Newly elected Chinese Academy of Sciences academicians in chemistry division in 2021

Advances in Soft Functional Materials Research

This special issue of Advanced Materials celebrates the 20th anniversary of the National Center for Nanoscience and Technology of China (NCNST), showcasing a diverse array of cutting-edge research in nanoscience and nanotechnology. This issue highlights recent advances in nanomaterials for devices, nanomedicine, energy, and catalysis applications. NCNST is a pioneering institution established on December 31, 2003 and supported by the National Development and Reform Commission. NCNST is the first state-level hub of the nation, dedicated to nanoscience innovation. The collaboration between the Chinese Academy of Sciences (CAS) and the Ministry of Education has place NCNST at the forefront of doing research, fostering talents, and engaging international exchange in the field of nanoscience and nanotechnology. Guided by the visionary leadership of Prof. Chunli Bai, former CAS president, NCNST has firmly established itself as a forerunner in nanoscience and nanotechnology over the past two decades. In 2021, 5 researchers from NCNST were honored as "Highly Cited Researchers" by Clarivate.[1] To connect the various disciplines within nanoscience and nanotechnology, three high impact nanoscience journals, i.e., Nanoscale, Nanoscale Advances, and Nanoscale Horizons, are published as a collaborative venture between NCNST and the Royal Society of Chemistry Publishing Group. In addition to these outstanding academic achievements, NCNST has successfully developed critical industrial technologies, resulting in innovations such as the "injectable irinotecan hydrochloride (nano) micelle product," which has garnered considerable commercial interest. The institute's strategic initiatives in research and technical standardization have played a pivotal role in shaping China's nanomeasurement standards, thus establishing a comprehensive array of standard substances and methodologies and positioning China as a leader in nano standards. NCNST's commitment to standards and regulations is evident from its affiliations with prominent bodies like the National Technical Committee 279 on Nanotechnology of Standardization Administration of China (SAC/TC 279), and the Special Committee on Nanotechnology of China National Accreditation Service for Conformity Assessment (CNAS). With rapid development for two decades, currently, NCNST has a faculty of 99 full professors and 110 associate professors, including 3 academicians of CAS, 15 Distinguished Young Scholars, and 26 Excellent Young Scholars from the National Natural Science Foundation of China. NCNST offers several doctoral and master's programs spanning a vast array of scientific disciplines, along with postdoctoral research opportunities. China's Academic Degrees Committee State Council approved "Nanoscience and Engineering" as a distinct academic discipline in 2022,[2] thus marking a pivotal milestone in the educational journey of the institute. The NCNST has three CAS Key laboratories including the Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, the Key Laboratory for Standardization and Measurement for Nanotechnology, and the Key Laboratory for Nanosystem and Hierarchical Fabrication. NCNST launched the Key Laboratory of Nanophotonic Materials and Devices to enhance its capabilities in 2020. The institute established specialized state-of-art labs for theoretical exploration, nanofabrication, and smart nanosensing, along with a Nanotechnology Development Department committed to establishing public research platforms and fortifying the study of nanotechnology. Celebrating its 20th anniversary, Advanced Materials honored NCNST by dedicating a special issue featuring 23 articles highlighting groundbreaking research in the fields of nanomaterials and devices, nanobiology and nanomedicine, energy and catalysis, etc. In the field of nanomaterials and devices, Prof. Ning Deng et al. (https://doi.org/10.1002/adma.202302658) present a novel M3D-SAIL chip architecture achieved through the monolithic 3D integration of a photosensor array, analog computing-in-memory (CIM), and Si CMOS logic circuits. This innovation demonstrates significant advantages for energy-efficient computing near sensors. Prof. Jin Zhang et al. (https://doi.org/10.1002/adma.202306129) explore the optimization of internal structure, including crystallinity, orientation, and porosity, of SWNTs in PBIA fibers. Prof. Xiangnan Sun et al. (https://doi.org/10.1002/adma.202301854) delve into the performance and functionalities of diverse emerging spintronic material systems. Prof. Erjun Zhou et al. (https://doi.org/10.1002/adma.202300175) review material development and voltage loss for A2-A1-D-A1-A2-type small molecules and their applications in ternary and indoor organic photovoltaics. Prof. Zhenxing Wang et al. (https://doi.org/10.1002/adma.202301472) discuss recent advances of 2D vdW ferroelectric materials in ferroelectricity origin and practical applications, especially in artificial intelligence. Prof. Luqi Liu et al. (https://doi.org/10.1002/adma.202303014) highlight recent advances on clean vdW interfaces to unlock potential of 2D materials in electronics and optoelectronics. Prof. Weiguo Chu et al. (https://doi.org/10.1002/adma.202303001) introduce the tailored nanostructure-dominated SPP effects for SPPs-based meta-devices and SERS meta-sensors. Prof. Xinghua Shi et al. (https://doi.org/10.1002/adma.202305758) provide an in-depth examination of principles and their implementation in machine learning interatomic potentials, focusing on applications in nanomaterial surface/interface systems and discussing the challenges inherent in this potent methodology. In the field of nanobiology and nanomedicine, Prof. Guangjun Nie et al. (https://doi.org/10.1002/adma.202211609) present a cell reprogramming-responsive hydrogel fabricated using a synthetic biology-based strategy. This hydrogel induces the formation of Yes-associated protein (YAP) biomolecular condensates at the appropriate stage during cell reprogramming, ensuring more efficient generation of induced pluripotent stem cells (iPSCs) than conventional methods. Prof. Yaoxin Lin et al. (https://doi.org/10.1002/adma.202306248) delineate an innovative tumor microenvironment-responsive nanorobot capable of effectively delivering nucleic acid drugs to TLR9-positive tumors. This research also demonstrates that CpG-loaded nanorobots have significant antitumor efficacy in cancer immunotherapy by inducing autophagy-mediated immunogenic cell death. Prof. Yuhong Cao et al. (https://doi.org/10.1002/adma.202303321) present a rapid and efficient method using wood-derived cellulose (WMC) to remove up to 98% of double-stranded RNA impurities from mRNA therapeutics within just 5 min. Prof. Baoquan Ding et al. (https://doi.org/10.1002/adma.202301035) provide an overview of recent advances in extracellular vesicle analysis using a variety of DNA-based nanomaterials and discuss unresolved challenges and future directions in this field. Prof. Chunying Chen et al. (https://doi.org/10.1002/adma.202303266) explore five different levels of physiological barriers faced by lipid-based nanoparticles for nucleic acid drug delivery and current coping strategies. Prof. Hao Wang et al. (https://doi.org/10.1002/adma.202305099) present a systematic and comprehensive overview of intelligent biomaterialomics to clarify the definition, formation mechanism, advanced characterization methods, potential applications, and future development directions. Prof. Hai Wang et al. (https://doi.org/10.1002/adma.202303180) discuss therapeutic strategies and clinical progress of ultrasound in neurological diseases, with a focus on the potential of ultrasound therapy based on upconversion nanoparticles (USINs) for neurological diseases. Prof. Xingjie Liang et al. (https://doi.org/10.1002/adma.202301770) explore the development of nanobiotechnology to enhance T-cell immunotherapy for disease treatment. Prof. Jiashu Sun et al. (https://doi.org/10.1002/adma.202303092) overview the recent advances in extracellular vesicle analysis using a variety of DNA-based nanomaterials, including linear DNA probes, DNA nanostructures, and hybrid DNA nanomaterials, and discuss unresolved challenges and perspective directions in this field. Prof. Lele Li et al. (https://doi.org/10.1002/adma.202302972) introduce modular engineering of aptamer-based nanotechnology, allowing conditional control of ATP sensing and imaging with high spatial precision from subcellular organelles to living animals. In the field of energy and catalysis, Prof. Zhiyong Tang et al. (https://doi.org/10.1002/adma.202305508) develop a structured p-CuSiO3/CuO for efficient CO2 reduction, demonstrating high stability and significant C2+ faradaic efficiency. Prof. Jianru Gong et al. (https://doi.org/10.1002/adma.202211008) present a porous cover structure with tunable pore sizes designed to enhance interfacial charge, mass transfer kinetics, and intrinsic catalytic activity of 2D-covered catalysts for improved photoelectrochemical water-oxidation reactions. Prof. Huiqiong Zhou et al. (https://doi.org/10.1002/adma.202303844) report semitransparent organic solar cells with homogeneous transmission and colorful reflection enabled by an ITO-free microcavity architecture. Prof. Zhixiang Wei et al. (https://doi.org/10.1002/adma.202302915) discuss molecular design and device optimization strategies for overcoming device performance bottlenecks in all-small-molecule organic solar cells, with a focus on improving charge management and reducing energy loss. Prof. Gang Liu et al. (https://doi.org/10.1002/adma.202301307) summarize the fundamental principles, synthetic methods, and latest progress of noble-metal-free single-atom catalysts (SACs) and dual-atom catalysts (DACs) in solar-light-driven artificial photosynthesis. We are honored to publish this special issue featuring innovations in nanomaterials at NCNST. We believe that the innovative spirit of research at NCNST, showcased in this Editorial, will propel the institute forward to greater achievements. Finally, we sincerely appreciate the tremendous support and kind cooperation of Dr. Sneha K Rhode, Dr. Xiaoge Hu, Dr. Yuhong Cao, Dr. Yanhong Ma, and the entire editorial team of Advanced Materials. The authors declare no conflict of interest. Qing Dai received his Ph.D. from the University of Cambridge and joined NCNST as a distinguished professor in 2012. He received the National Science Fund for Distinguished Young Scholars and the Science and Technology Award for Chinese Youth in 2019. Currently, he serves as a distinguished professor at the Chinese Academy of Sciences and a fellow of the Royal Society of Chemistry. His research interests include the synthesis of ultrathin 2D nanomaterials and the fabrication of low-dimensional nanomaterial devices for various applications. Zhixiang Wei received his Ph.D. from the Institute of Chemistry, Chinese Academy of Sciences, in 2003. He earned his B.S. and M.S. degrees from Xi'an Jiaotong University in 1997 and 2000, respectively. He served as a postdoctoral fellow at the Max Planck Institute of Colloids and Interfaces and the University of Toronto in 2003–2004 and 2005, respectively. Prof. Wei joined the NCNST as a Principal Investigator in 2006. His research interests include organic functional nanomaterials and flexible devices. Zhiyong Tang, the Director-General of NCNST, was elected as Member of the Chinese Academy of Sciences in 2023. He earned his Ph.D. from Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, in 2000 and his B.S. and M.S. degrees from Wuhan University in 1993 and 1996, respectively. Following 6 years of experience as a postdoctoral fellow at Swiss Federal Institute of Technology, Zurich, Oklahoma State University, and University of Michigan, he joined NCNST as a Principal Investigator in November 2006. His research interests primarily focus on the fabrication, assembly, and applications of inorganic nanomaterials in energy and catalysis. Yuliang Zhao was elected as Member of the Chinese Academy of Sciences in 2017 and a fellow of the World Academy of Sciences in 2018. He graduated from Sichuan University in 1985, and received his Ph.D. from Tokyo Metropolitan University in 1999. Prof. Zhao joined the Chinese Academy of Sciences as a Principal Investigator in 2001. His research interest primarily focuses on the toxicity study of engineered nanomaterials and cancer nanomedicine. He served as the Director-General of NCNST from September 2018 to October 2023.

<i>ChemNanoMat</i>-A New Journal for Small Science with a Big Impact

First of all, I, together with my colleagues and friends, would like to send our best wishes to Professor Daoben Zhu on the occasion of his 75th birthday. Professor Zhu began his chemistry studies at East China University of Science and Technology (ECUST) in 1965 and graduated in 1968. He then joined the Institute of Chemistry, Chinese Academy of Sciences as an assistant professor, and was promoted to associate professor in 1985 and professor at 1987. He was a visiting scholar at the Max-Planck Institute for Medical Research in Heidelberg, Germany, from 1977 to 1979. He again worked as a visiting scientist at the same Max-Planck Institute in 1985 and 1986. Professor Zhu is one of the pioneers in the area of molecular materials and devices in China. He has been the director of the CAS Key Laboratory of Organic Solids since its establishment. He and his co-workers have made remarkable contributions to interdisciplinary cutting-edge research areas including organic conductors and superconductors, functional Langmuir–Blodgett films, fullerene chemistry and physics, light-emitting materials and devices, organic semiconductors and devices, and organic thermoelectronic materials and devices. These research achievements have provided in-depth understanding of the electronic processes and related phenomena in organic solids, thus boosting research into molecular materials and devices. Professor Zhu has published two books and more than 1000 papers in scientific journals, which have received more than 24 000 citations, and has an H-index of 90. His research accomplishments have been well recognized by the scientific community. He has received National Natural Sciences of China second-class prizes five times, in 1988, 2002, 2004, 2007 and 2014. He was the winner of the Chinese Chemical Society—the China Petroleum and Chemical Corporation Chemical Contribution Award in 2008, and he won the Tan Kah Kee Science Award in chemistry in 2012. Professor Zhu was elected as a Chinese Academy of Sciences Academician in 1997 and a member of the World Academy of Sciences for the advancement of science in developing countries in 2009. In 2014 and 2015, Professor Zhu was selected by Thomson Reuters as one of the world's most influential scientific minds both in chemistry and materials science. Apart from doing scientific research, Professor Zhu has made great contributions to the administration and management of scientific research in China. Among the administration positions he has held, he was the director of the Institute of Chemistry, Chinese Academy of Sciences from 1992 to 2000, vice president of the National Natural Science Foundation of China from 2000 to 2007, president of the Chinese Chemical Society from 1994 to 1997, and vice president of the Chinese Materials Society from 2001 to 2005. He was the vice chairman of the second, fourth and fifth advisory committees of the National Basic Research Program of China (973 Program). He is now the vice chairman of the Academic Committee of Chinese Academy of Sciences (CAS) and the committee chair of the Academic Division of Chemistry, CAS. Professor Zhu has continuously supported and actively promoted scientific exchanges and collaborations between Chinese scientists and leading scientists across the world. We publish this special issue to celebrate the 75th birthday of Professor Zhu and express sincere thanks to him for his continuous support over many years. This special issue collects research communications, full research papers, and reviews that cover the following topics: organic semiconductors, doping of organic semiconductors and field-effect transistors, graphdiyne and carbon ene-yne nanoribbon, photovoltaic cells and photodetectors, bioelectronics, and organic nonlinear optical materials. We would like to take this opportunity to thank the distinguished authors who contributed to this special issue, and the editorial staff of Advanced Electronic Materials for enabling its publication. Professor Yuliang Li has worked at the Institute of Chemistry, Chinese Academy of Sciences since 1975. He was a visiting scholar in the Department of Chemistry at University of Amsterdam (The Netherlands) from 1987 to 1989, was a visiting professor at the Radiation Lab at University of Notre Dame (USA) from August 1998 to March 1999, and worked in the Department of Chemistry at the University of Hong Kong from September 1999 to February 2000. His research interests include the growth of low-dimensional and two-dimensional carbon nanostructures, covalently and non-covalently assembled molecular materials, and supramolecular chemistry.

Open AccessCCS ChemistryRESEARCH ARTICLE7 Dec 2022Tumor-Selective Cascade-Amplified Dual-Prodrugs Activation for Synergistic Oxidation-Chemotherapy Xuan Xiao†, Qingyu Zong†, Jisi Li and Youyong Yuan Xuan Xiao† School of Biomedical Sciences and Engineering, South China University of Technology, Guangzhou 511442 National Engineering Research Center for Tissue Restoration and Reconstruction, South China University of Technology, Guangzhou 510006 †X. Xiao and Q. Zong contributed equally to this work.Google Scholar More articles by this author , Qingyu Zong† National Engineering Research Center for Tissue Restoration and Reconstruction, South China University of Technology, Guangzhou 510006 School of Medicine, South China University of Technology, Guangzhou 510006 †X. Xiao and Q. Zong contributed equally to this work.Google Scholar More articles by this author , Jisi Li National Engineering Research Center for Tissue Restoration and Reconstruction, South China University of Technology, Guangzhou 510006 School of Medicine, South China University of Technology, Guangzhou 510006 Google Scholar More articles by this author and Youyong Yuan *Corresponding author: E-mail Address: [email protected] School of Biomedical Sciences and Engineering, South China University of Technology, Guangzhou 511442 National Engineering Research Center for Tissue Restoration and Reconstruction, South China University of Technology, Guangzhou 510006 Key Laboratory of Biomedical Materials and Engineering of the Ministry of Education, South China University of Technology, Guangzhou 510006 Guangdong Provincial Key Laboratory of Biomedical Engineering, South China University of Technology, Guangzhou 510006 Google Scholar More articles by this author https://doi.org/10.31635/ccschem.022.202101564 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Efficacy of prodrugs in cancer therapy requires selective and efficient drug activation in cancer cells. Here, we report a novel dual-prodrug delivery system with tumor-selective cascade-amplified prodrug activation for synergistic oxidation-chemotherapy. Cancer cells overexpressing cathepsin B-activatable near-infrared (NIR) hemicyanine prodrug (CyNH-Citval) were encapsulated by the reactive oxygen species (ROS)-responsive polyprodrug of doxorubicin (DOX) (PTKDOX) to obtain PTKDOX/Cy. Upon uptake of PTKDOX/Cy by cancer cells and subsequent prodrug CyNH-Citval activation, NIR fluorescence was turned on and toxicity toward mitochondria was restored, thereby elevating intracellular ROS levels, which subsequently activated the polyprodrug PTKDOX to initiate the cascade and amplify DOX. Overall, these results indicate that enzyme-mediated initiation of drug activation and amplification of cascade ROS ultimately causes selective and efficient prodrug activation in tumors with synergistic oxidation and chemotherapy. These findings provide new insights to inform precise cooperative cancer therapy. Download figure Download PowerPoint Introduction Although chemotherapy is a major clinical approach for tumor therapy, its application remains constrained by poor selectivity and serious side effects.1–3 To improve the selectivity and therapeutic efficacy of chemotherapy, various stimulus-responsive drug delivery systems (DDSs) have been developed in the past decade.4–6 For example, numerous research has focused on prodrugs that are specifically activated by tumor associated stimuli to release the potent naïve drug which allows them to improve selectivity of chemotherapy.6–8 Various stimuli, including pH,9,10 glutathione,11,12 reactive oxygen species (ROS),13–15 and enzymes,16,17 are present in tumor microenvironments. Thus, tumor-associated enzyme-activated prodrugs have received numerous attention due to the high selectivity of enzymes overexpressed in cancer cells.18–23 However, use of enzyme-activated prodrugs is limited by ineffective drug activation owing to the paucity of tumor-associated enzymes that represent an essential step for the functioning of the prodrug.24,25 For example, Chen and co-workers26 amplified prodrug activation by sequentially delivering combretastatin A4 to upregulate metalloproteinase 9 (MMP9) and MMP9-activated doxorubicin (DOX) prodrug and promoted activation of tumor-selective prodrug for cancer therapy. In addition, Yin and co-workers27 reported that a pro-protein therapy was activated by self-amplified hypoxia associate enzymes. Consequently, development of an enzyme-responsive prodrug, which can simultaneously retain selectivity of enzyme-responsiveness for tumor targeting and amplification of the enzyme response signal for enhanced therapeutic efficiency, remains a great challenge. Recently, numerous research groups have exploited the ability of cancer cells to overproduce ROS to develop ROS-responsive DDSs containing oxidation-labile groups, such as thioketal, boronic ester, and proline, for cancer treatment.28 However, intracellular concentration of ROS is still not high enough for efficient drug activation, which represents an intrinsic limitation for the ROS-responsive systems despite their great potential.29–31 For example, Mokhir and co-workers29 reported an ROS-dependent aminoferrocene-based prodrug that amplified intracellular ROS level for efficient cancer therapy. Therefore, development of new strategies for enzyme-activated ROS generation is imperative to improvement of tumor selectivity. The generated ROS can be further utilized for efficient prodrug activation. In this study, we developed a tumor-selective cascade-amplified dual-prodrug activation system (denoted PTKDOX/Cy) consisting of cancer cells overexpressing cathepsin B (CTB), CTB-activated hemicyanine (CyNH2) prodrug (CyNH-Citval), and ROS-responsive polyprodrug of DOX (PTKDOX) conjugated on the side chain of poly(thioketal) (PTK; Schemes 1a and 1b). Previous studies have shown that amino containing near-infrared (NIR) CyNH2 can selectively accumulate in mitochondria and efficiently lower their membrane potential, thereby increasing intracellular ROS levels to cause oxidation-induced cell death.32 Prior to activation, the prodrug CyNH-Citval shows a weak fluorescence due to intramolecular charge transfer (ICT) and low toxicity, which can reduce its toxicity to normal cells.33,34 Upon interacting with CTB overexpressed in cancer cells, CyNH2 is activated to restore toxicity, and NIR fluorescence is triggered for drug activation monitoring. Activated CyNH2 leads to mitochondrial dysfunction in cancer cells, thereby elevating levels of intracellular ROS. Consequently, high ROS levels mediate activation of the polyprodrug PTKDOX, thereby initiating a cascade and amplifying the DOX prodrug. More importantly, CyNH2 and DOX showed synergistic oxidation and chemotherapy. Moreover, CyNH-Citval exhibited low toxicity and insignificant elevation of ROS levels in normal cells due to the low CTB expression. This phenomenon disrupted initiation of cascade DOX activation and resulted in low cytotoxicity of PTKDOX/Cy to normal cells. Integrating dual prodrugs into a single PTKDOX/Cy with cascade and amplified drug activation may increase tumor selectivity and efficiency of drug activation for synergistic oxidation-chemotherapy of cancer. Scheme 1 | Profile of the tumor-selective cascade-amplified dual-prodrug activation system (PTKDOX/Cy) developed in this research. (a) Chemical structure. (b) Schematic representation of the tumor-selective cascade-amplified dual-prodrugs activation for synergistic oxidation-chemotherapy. Download figure Download PowerPoint Experimental Methods Details of the materials and instruments utilized are provided in the Supporting Information. Preparation of PTKDOX and PTKDOX/Cy CyNH-Citval was synthesized by conjugating CyNH2 with CTB-specific citrulline-valine (Cit-Val) peptide linker. PTK was obtained by fast polycondensation of 1,3-dimercapto-2-propanol and acetone, with a molar ratio of 1∶1.05, in the presence of concentrated hydrogen chloride (HCl). Then PTK pyridine (PTK-SS) was obtained by the disulfide-thiol exchange reaction of PTK with 2,2′-dithiodipyridine at a molar ratio of 1∶3. Finally, PEG-TK-DOX (TK = polythioketone) was first synthesized via conjugating DOX and PEG with a fixed ratio of 10∶1 to the hydroxyl groups of PTK-SS. Then PEG-PTK-DOX (30 mg) was dissolved in 1 mL of dimethyl sulfoxide (DMSO), and then gradually added into 9 mL of ultrapure water under stirring. After additional stirring for 2 h, the solution was transferred into a dialysis bag (MWCO 3500) to remove DMSO against ultrapure water for 24 h, and then the solution was filtered through a 0.45 μm filter to obtain PTKDOX. The preparation of PTKDOX/Cy was similar to that for PTKDOX, but the polymer PEG-PTK-DOX was replaced with PEG-PTK-DOX and CyNH-Citval (1.0 mg). Cell culture and tumor model Mouse breast cancer cell line 4T1 cells were cultured in Roswell Park Memorial Institute 1640 medium with 10% fetal bovine serum and 1% penicillin-streptomycin. Cell cultures were incubated in a 5% CO2 and 21% O2 incubator at 37 °C. Female BALB/c mice and BALB/c nude mice (20 ± 2 g, 6–8 weeks old) were purchased from Hunan SJA Laboratory Animal Co. Ltd (Hunan, China). 4T1 cells (1 × 106) were injected into the right mammary fat pads to establish an orthotopic 4T1 tumor model. After the tumor volumes reached 100 mm3, the mice were used for subsequent experiments. At the end of experiments, all mice were killed by CO2 inhalation. All animal experiments were approved by the Ethics Committee of the South China University of Technology (Guangzhou, China). All detailed experimental methods are available in the Supporting Information. Results and Discussion Preparation and characterization of PEG-TK-DOX and CyNH-Citval A summary of synthetic routes to the NIR CyNH2 is presented in Supporting Information Scheme S1. The structure and purity of CyNH2 and intermediates were confirmed by 1H NMR spectra ( Supporting Information Figures S1–S6). The synthetic method for preparation of the prodrug CyNH-Citval is displayed in Supporting Information Scheme S2. Briefly, CyNH2 was conjugated with CTB-specific Cit-Val peptide linker to obtain the prodrug CyNH-Citval with a yield of 11.6%. Thereafter, the prodrug and its intermediates were verified via 1H NMR spectra ( Supporting Information Figures S7 and S8). The synthetic route of polyprodrug PTKDOX is shown in Supporting Information Scheme S3. In brief, PTK was obtained by rapid polycondensation of 1,3-dimercapto-2-propanol and acetone, with a molar ratio of 1∶1.05, in the presence of concentrated HCl. PTK appeared as a colorless waxy solid, with a 47% yield and 14 repetitive units, after contrastive analysis of integration intensities of peaks 1 (methylene protons of PTK) and 2 (sulfhydryl protons of 1,3-dimercapto-2-propanol) from the 1H NMR spectra ( Supporting Information Figures S9 and S10). Subsequently, PTK-SS was obtained, as a light-yellow solid, by the disulfide-thiol exchange reaction of PTK with 2,2′-dithiodipyridine, at a molar ratio of 1∶3. Next, PTK-SS was activated with N,N′-carbonyldiimidazole (CDI) then conjugated with DOX and amino-terminated methoxy poly(ethylene glycol) (PEG) to obtain polyprodrug PTKDOX. 1H NMR spectra revealed that the grafting rate for DOX was about 50% ( Supporting Information Figure S13). Moreover, 1H NMR spectra, 13C NMR spectra, MS spectra, and gel permeation chromatography studies were used for characterization analysis of the new compounds, polymers, and their intermediates ( Supporting Information Figures S1–S32 and S34A). The fluorescence change of CyNH-Citval in response to papain Results of analysis of CyNH2 and CyNH-Citval absorption are shown in Supporting Information Figure S34b. Summarily, CyNH2 had a maximum absorption of 710 nm, whereas that of CyNH-Citval blue-shifted to 615 nm, which is attributed to ICT of CyNH-Citval.33,34 In addition, CyNH2 exhibited a strong fluorescence intensity, whereas that of CyNH-Citval was weak, further affirming the ICT of CyNH-Citval ( Supporting Information Figure S34c). Next, we chose papain as a substitute enzyme for analysis of CyNH-Citval’s enzyme-response behavior, due to its similar enzyme activity to CTB,35 and investigated fluorescence changes of CyNH-Citval after treatment with different concentrations of papain over time. CyNH-Citval’s fluorescence intensity increased with prolonged incubation times, reaching saturation after 6 h with a papain concentration of 10 mM ( Supporting Information Figure S34d). In addition, CyNH-Citval’s fluorescence intensity increased upon increased papain concentration, reaching saturation upon addition of 10 μM papain after 6 h (Figure 1a). Notably, this fluorescence intensity increased ∼15-fold and exhibited papain concentration dependence over a wide range (0–10 μM). These results indicated that papain could effectively cleave the amide bond of CyNH-Citval, and release CyNH2 with strong fluorescence activation. Therefore, a high concentration of CTB in cancer cells may cause a release of CyNH2 and turn-on NIR fluorescence. Figure 1 | (a) Fluorescence spectra of CyNH-Citval treated with different concentrations of papain. (b) UV–vis absorbance spectra of DOX, CyNH-Citval, and PTKDOX/Cy. (c) Changes in hydrodynamic diameter of PTKDOX/Cy after treatment with H2O2, ClO−, or ·OH. (d) 1H NMR spectrum for H2O2-responsive degradation of PTK-SS with generation of acetone after treatment with DMSO-d6 and H2O2 (10 mM) at 37 °C. (e) Fluorescence spectra for DOX, PTKDOX, and PTKDOX/Cy. (f) Cumulative release of DOX from PTKDOX/Cy in the presence of different concentrations of H2O2. Download figure Download PowerPoint In vitro ROS-responsive degradation and DOX release Next, we employed a nanoprecipitation method to prepare PTKDOX/Cy by self-assembly from PEG-PTK-DOX via encapsulation of CyNH-Citval. Results showed that PTKDOX/Cy had a hydrodynamic diameter of ∼107 nm in phosphate-buffered saline (PBS) (Figure 1c). In addition, PTKDOX/Cy exhibited an absorbance spectrum with similar absorbance to DOX and CyNH-Citval, with maximum absorption at 480 and 615 nm, respectively (Figure 1b and Supporting Information Figure S34b), indicating that DOX and CyNH-Citval were successfully loaded. DOX and CyNH-Citval had loading capacities of 33.67 ± 0.23 and 9.13 ± 0.25%, respectively. Meanwhile, PTKDOX/Cy’s hydrodynamic diameter changed from 107 nm in PBS, to 10 nm after treatment with H2O2, ClO− or ·OH (Figure 1c), indicating that it was degraded in response to ROS. Also, transmission electron microscopy (TEM) and scanning electron microscopy images recorded for PTKDOX/Cy are shown in Supporting Information Figures S33a and S33c, and the TEM image recorded for PTKDOX/Cy after treatment with 10 mM H2O2 and 10 μM papain is shown in Supporting Information Figure S33b. Furthermore, 1H NMR spectra revealed H2O2-triggered degradation of PTK-SS (Figure 1d) as well as the disassociation mechanism of PTKDOX ( Supporting Information Figure S35). Degradation of PTK-SS (15 mg mL−1) was detected using a commixture of DMSO-d6 and H2O2 (10 mM), while the thioketal of PTK-SS eventually turned into acetone (Figure 1d). The fluorescence of DOX in PTKDOX/Cy was inhibited by the Förster resonance energy transfer of DOX to CyNH2 and aggregation-caused quenching of DOX (Figure 1e). Next, we studied drug release of the PTKDOX/Cy and found almost no or moderate release of free DOX in the presence of PBS and 1 mM H2O2, respectively (Figure 1f). Conversely, large amounts of DOX were released in the presence of 10 mM H2O2, indicating that more drug could be released in cells with high H2O2 concentrations. The critical micelle concentration of PTKDOX PTKDOX can itself induce the formation of polymeric nanoparticles. To evaluate the critical micelle concentration (CMC), we measured the count rates of nanoparticles at different concentrations according to the previous literature.36 As shown in Supporting Information Figure S36a, the CMCs of PTKDOX nano-assembly is 0.0728 mg/mL. The dynamic light scattering data revealed that the size of obtained PTKDOX nanoparticles was about 73.2 nm ( Supporting Information Figure S36b). In vitro CyNH2 release and the cellular uptake mechanism for the PTKDOX/Cy Analysis of the release behavior of CyNH2 from PTKDOX/Cy in the presence of both ROS (10 mM H2O2) and enzyme (10 μM papain) ( Supporting Information Figure S37a) shows the cumulative release of CyNH2 was <5% in phosphate buffer at 37 °C after 48 h, which means negligible leakage before the prodrug reaches the tumor site. When H2O2 or papain was added, the release of CyNH2 was <10%. In contrast, the cumulative release amount of CyNH2 was 72.4% after 48 h in the presence of H2O2 and papain. These results indicate that CyNH2 only can be released when H2O2 and papain were simultaneously present. The endocytic pathway of PTKDOX/Cy by cancer cells was investigated in the presence of several endocytosis inhibitors including chlorpromazine (inhibitor of clathrin-mediated endocytosis), methyl-β-cyclodextrin (inhibitor of caveolae-mediated endocytosis), and amiloride (inhibitor of giant pinocytosis). As shown in Supporting Information Figure S37b, the cells treated with chlorpromazine at 4 °C showed lower nanoparticle internalization, suggesting that PTKDOX/Cy is susceptible to a clathrin-mediated endocytotic pathway in 4T1 cells in an energy-dependent manner. Intracellular fluorescence recovery of PTKDOX/Cy Next, we performed confocal image analysis on mouse breast cancer cell line 4T1 and the mouse embryonic fibroblast (MEF) cell line MEF to evaluate PTKDOX/Cy’s applicability in cancer therapy and imaging. Results revealed strong red fluorescence signals in both CyNH-Citval and PTKDOX/Cy-treated 4T1 cells, with ∼10- and 6-fold increases in the mean fluorescence intensity (MFI), respectively, relative to MEF cells (Figure 2a and Supporting Information Figure S38). In contrast, pretreatment of 4T1 cells with CA-074 methyl ester (CA-074-Me), a CTB inhibitor, resulted in diminished fluorescence. Overall, these results indicated selective activation of CyNH-Citval and PTKDOX/Cy fluorescence in 4T1 tumor cells, making it promising for tumor-specific intelligent images. Figure 2 | (a) Confocal microscopy images showing fluorescence of CyNH2 (red) in 4T1 and MEF cells after incubation with CyNH-Citval or PTKDOX/Cy for 6 h. Inhi. represents the CTB inhibitor CA-074-Me, which was preincubated with the cells for 2 h. (b) Confocal microscopy images showing intracellular ROS levels stained with DCFH-DA (green) in 4T1 and MEF cells after different treatments. VC represents ROS scavenger vitamin C. (c) Cytotoxicity of 4T1 and MEF cells incubated with CyNH2 or CyNH-Citval. (d) Cytotoxicity of 4T1 cells treated with PTKDOX, PTKDOX/Cy, and PTKDOX/Cy+VC. Statistical significance: *P < 0.05, **P < 0.01. Download figure Download PowerPoint Colocalization of CyNH2 with mitochondria and mitochondrial membrane potential study Furthermore, we found good colocalization between CyNH2 and MitoTracker Green-labeled mitochondria, as evidenced by a colocalization coefficient of 0.83 ( Supporting Information Figure S39). Next, we explored mitochondrial membrane potentials (MMPs) using in 4T1 cells the probe 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethyl-imidacarbocyanine iodide (JC-1). Results showed that JC-1 could assemble into J-aggregates, with red fluorescence in high MMP mitochondrial matrix, but dispersed into the cytoplasm in a monomeric form with green fluorescence in low MMP mitochondrial matrix. Notably, cells treated with CyNH-Citval and CyNH2 exhibited marked green fluorescence ( Supporting Information Figure S40), indicative of a gradual decrease in MMP, although cells treated with CyNH-Citval+Inhi CTB inhibitor exhibited a weak green fluorescence. Intracellular ROS level The decrease in MMP, by may be attributed to ROS explored and ROS in 4T1 cells using the ROS which is by ROS and subsequently into with green fluorescence. Results revealed strong green fluorescence in cells treated with CyNH2 and PTKDOX/Cy, with an and increase in the respectively, relative to PBS or DOX (Figure and Supporting Information Figure in the which had been with ROS scavenger vitamin and CTB inhibitor CA-074-Me, exhibited a weak fluorescence these results confirmed that CyNH2 can intracellular ROS which can be further utilized to DOX. Intracellular DOX release To ROS levels by released CyNH2 could amplify DOX activation, we employed confocal scanning to intracellular DOX release from PTKDOX and PTKDOX/Cy in 4T1 cells. Results showed that 4T1 cells exhibited red fluorescence after incubation with PTKDOX and PTKDOX/Cy for 6 h (Figure A further h incubation resulted in a weak red fluorescence signal in the with indicating that only a amount of DOX was released in cells treated with PTKDOX. Conversely, a strong red fluorescence signal was in the of cells treated with PTKDOX/Cy, indicative of enhanced activation of DOX with PTKDOX/Cy. Next, we employed to evaluate concentrations of DOX in 4T1 cells, after incubation with PTKDOX and PTKDOX/Cy over time. Results showed that cells treated with PTKDOX/Cy had a increase in the amount of released DOX relative to treated with PTKDOX at h ( Supporting Information Figure These results indicated that the released CyNH2 from PTKDOX/Cy with ROS levels amplified the DOX activation in the tumor cells. In vitro cytotoxicity and cellular Next, we employed the to the cytotoxicity of CyNH-Citval and CyNH2 to more of cell cancer cell mouse cancer cell line and mouse cell line cells and cells had lower MEF and cells (Figure and Supporting Information Figure indicating that CTB-activated prodrug CyNH-Citval tumor-specific Moreover, DOX and CyNH2 had a synergistic on 4T1 cells, as evidenced by a of ( Supporting Information Figure Furthermore, we investigated PTKDOX, PTKDOX/Cy, and cytotoxicity on 4T1 cells, at different DOX and found that PTKDOX whereas PTKDOX/Cy had toxicity PTKDOX and the concentration of in 4T1 cells (Figure In contrast, PTKDOX/Cy had low activity in the presence of indicating that increased activation of DOX was on this marked cytotoxicity of PTKDOX/Cy to 4T1 cells, we explored cellular using the Results showed that PTKDOX/Cy treatment cellular PTKDOX, whereas cell increased addition of VC or the inhibitor ( Supporting Information Figure which results from the In study of PTKDOX/Cy Results from in NIR fluorescence images of PTKDOX/Cy in 4T1 nude mice revealed strong fluorescence in tumors of mice injected with PTKDOX/Cy to treated with and the fluorescence was in the tumors to 48 h (Figure and Supporting Information Figure the tumors and major 48 h after of PTKDOX/Cy and to obtain images. Results revealed fluorescence intensity in tumors of mice treated with PTKDOX/Cy relative to the while a weak intensity was in the treated with ( Supporting Information Figure These results indicated that PTKDOX/Cy was selectively in and precise in images. To the efficacy of PTKDOX/Cy in we fluorescence intensity of CyNH2 and ROS levels in tumor after treatment with PTKDOX/Cy and Results showed strong fluorescence intensities in and CyNH2 from PTKDOX/Cy-treated but weak in ( Supporting Information Figure the release of CyNH2 and elevation of ROS levels in tumor which was with results from the in vitro cell these results provide further that CyNH2 from PTKDOX/Cy is activated with NIR fluorescence for drug activation and the activated CyNH2 causes mitochondria dysfunction in cancer cells and increases levels of intracellular ROS in tumor Figure | (a) In NIR fluorescence images of nude mice 4T1 after with PTKDOX/Cy and fluorescence images. (b) Changes in tumor volumes in 4T1 mice under different treatments. (c) tumor of mice under different treatments. (d) of tumors in mice after and at the end of the therapy in response to different treatments. = 100 Statistical significance: *P < 0.05, **P < < Download figure Download PowerPoint In of PTKDOX/Cy Next, we efficacy of PTKDOX/Cy in using mice 4T1 The mice were the tumors to mm3, into groups, and treated with PBS, free DOX, PTKDOX, and PTKDOX/Cy mg respectively, via Thereafter, we measured and recorded the tumor volumes and 2 Results showed that mice treated with DOX and PTKDOX exhibited tumor to relative to in the PBS (Figure However, tumors in mice treated with PTKDOX/Cy and were Notably, PTKDOX/Cy treatment exhibited the therapeutic efficiency, as evidenced by a tumor rate of with the tumor relative to the results were in tumor and images (Figure and Supporting Information Figure Notably, of mice treated with PTKDOX/Cy were almost indicating great of the prodrug PTKDOX/Cy to mice ( Supporting Information Figure Moreover, results from and of major revealed a negligible after PTKDOX/Cy relative to PBS, which PTKDOX/Cy’s ( Supporting Information Figure Furthermore, analysis of tumors from mice in the PTKDOX/Cy revealed that a great of tumor cells was and the (Figure results were obtained after end as evidenced by the green fluorescence. successfully a dual-prodrug delivery a tumor-selective cascade amplified prodrug activation, for synergistic oxidation-chemotherapy. prodrug, not only therapy with high tumor selectively but ROS for efficient activation of prodrug DOX. CyNH-Citval could be activated by CTB overexpressed in 4T1 tumor cells, relative to normal MEF cells, whereas activated CyNH2 a increase in intracellular ROS which further enhanced DOX activation by to PTKDOX. Moreover, PTKDOX/Cy resulted in the in therapeutic efficacy against 4T1 as evidenced by a tumor which was in to PTKDOX these findings indicate that dual-prodrugs with enzyme-responsive drug release is a promising for selectivity and therapeutic efficacy of cancer therapy. The was through of all All have to the of the Supporting Information Supporting Information is available and the of the and TEM images as well as the of in vitro DOX the fluorescence change of CyNH-Citval in response to confocal image and colocalization of CyNH2 with mitochondria, MMP study, intracellular ROS level intracellular DOX in vitro cytotoxicity and cellular in study, in of PTKDOX/Cy, and additional Figures of The no This was by the National of China and the and Technology of Guangzhou Guangdong Provincial the for the of Key in Guangzhou Key Laboratory of and as an for Cancer Google Scholar and Google Scholar on A in the against Cancer with a Google Scholar for Google Scholar in Google Scholar Xiao Yuan with a for Synergistic Google Scholar for and Cancer Google Scholar Chen for the of and of Google Scholar Li A for to in Cancer Google Scholar C. of to Google Scholar for and Cancer Google Scholar Xiao Zong Yuan with and Activation for Google Scholar for Google Scholar a Google Scholar Chen Chen Materials for and Google Scholar Chen of for Google Scholar and of into Google Scholar in Cancer Google Scholar and Google Scholar for and Google Scholar for Google Scholar of Cancer and Google Scholar Park Park of for Cancer Google Scholar Park that in to Google Scholar for Google Scholar Li Chen A4 of Google Scholar Li Yin by a Google Scholar Chen Google Scholar Mokhir of as Google Scholar Li of a H2O2 for Google Scholar Chen by Google Scholar Cancer a with Google Scholar for of Google Scholar Yuan for between the and Google Scholar Li Q. and for and Google Scholar C. 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Open AccessCCS ChemistryCOMMUNICATIONS2 Sep 2022Towards Efficient Blue Delayed-Fluorescence Molecules by Modulating Torsion Angle Between Electron Donor and Acceptor Jinke Chen, Xing Wu, Hao Liu, Nuoling Qiu, Zhangshan Liu, Dezhi Yang, Dongge Ma, Ben Zhong Tang and Zujin Zhao Jinke Chen State Key Laboratory of Luminescent Materials and Devices, Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates, South China University of Technology, Guangzhou 510640 , Xing Wu State Key Laboratory of Luminescent Materials and Devices, Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates, South China University of Technology, Guangzhou 510640 , Hao Liu State Key Laboratory of Luminescent Materials and Devices, Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates, South China University of Technology, Guangzhou 510640 , Nuoling Qiu State Key Laboratory of Luminescent Materials and Devices, Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates, South China University of Technology, Guangzhou 510640 , Zhangshan Liu State Key Laboratory of Luminescent Materials and Devices, Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates, South China University of Technology, Guangzhou 510640 , Dezhi Yang State Key Laboratory of Luminescent Materials and Devices, Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates, South China University of Technology, Guangzhou 510640 , Dongge Ma State Key Laboratory of Luminescent Materials and Devices, Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates, South China University of Technology, Guangzhou 510640 , Ben Zhong Tang School of Science and Engineering, Shenzhen Institute of Aggregate Science and Technology, The Chinese University of Hong Kong, Shenzhen, Guangdong 518172 AIE Institute, Guangzhou Development District, Huangpu, Guangzhou 510530 and Zujin Zhao *Corresponding author: E-mail Address: [email protected] State Key Laboratory of Luminescent Materials and Devices, Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates, South China University of Technology, Guangzhou 510640 https://doi.org/10.31635/ccschem.022.202202196 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Constructing blue thermally activated delayed-fluorescence materials for high-performance organic light-emitting diodes (OLEDs) remains challenging due to the intrinsically strong intramolecular charge transfer nature of the nearly orthogonal connection of electron donor (D) and acceptor (A), which results in long-wavelength emission. Herein, an effective delayed-fluorescence design strategy of modulating D–A torsion angles is proposed and efficient sky-blue, pure-blue, and deep-blue delayed-fluorescence molecules consisting of a xanthenone acceptor and carbazole-based donors are created by decreasing the torsion angles. They exhibit strong delayed fluorescence with high photoluminescence quantum yields of 85–94% in doped films, and their delayed-fluorescence lifetimes are elongated from 1.0 to 27.6 μs as the torsion angles decrease. These molecules can function as excellent emitters in OLEDs, providing efficient electroluminescence peaking at 442 nm (CIEx,y = 0.15, 0.08), 462 nm (CIEx,y = 0.15, 0.18), and 482 nm (CIEx,y = 0.17, 0.30) with state-of-the-art external quantum efficiencies of up to 22.2%, 33.7%, and 32.1%, respectively, demonstrating the proposed molecular design for efficient blue delayed-fluorescence molecules is successful and promising. Download figure Download PowerPoint Introduction Efficient blue organic luminescent materials are highly desired because they are one of the fundamental elements of the three primary colors in organic light-emitting diodes (OLEDs).1–7 Organic fluorescence molecules with blue emission, which are employed as the first-generation luminescent materials in OLEDs, can be readily designed, but only 25% of the electro-generated excitons under electrical excitation are used, leading to low external quantum efficiency with an upper limit of 5–7.5%.8–10 Several strategies, such as triplet–triplet fusion11–13 and hybridized local and charge-transfer excited states,14–17 have been proposed to enhance triplet exciton utilization of fluorescence molecules, but full exciton harvesting remains difficult. Second-generation noble-metal-containing phosphorescence materials have been developed, which can reach unity exciton utilization by converting singlet excitons to triplet excitons via intersystem crossing based on heavy-atom induced large spin–orbit coupling (SOC). But, because of the intrinsic metal-to-ligand charge-transfer (CT) characteristics, pure blue emissions are hardly achieved in most phosphorescence materials, and the long lifetimes of triplet excitons result in poor stability of these materials in OLEDs.18–21 After decades of continuous research, purely organic thermally activated delayed-fluorescence (TADF) molecules have been invented and are currently emerging as the third-generation luminescent materials for the fabrication of high-performance OLEDs, thanks to the advantages of easy molecular design, high exciton utilization, noble metal-free structures, and so on.1,22–28 The reported TADF molecules generally have a highly twisted conformation, consisting of an electron donor (D) and acceptor (A) connected in a nearly perpendicular manner, to minimize the exchange integral between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). Thus, the energy split (ΔEST) between the lowest singlet excited (S1) state and the lowest triplet excited (T1) state can be reduced to allow fast reverse intersystem crossing (RISC), which results in the occurrence of delayed fluorescence.3,29–31 Although numerous efficient sky-blue to red TADF molecules have been successfully explored based on this design method,24,31–37 deep-blue to blue TADF molecules are still challenging because these nearly orthogonal D–A systems are inevitably accompanied by a strong intramolecular charge-transfer (ICT) effect that causes redshifted emissions.38–41 Weakening the ICT effect by choosing weak D and A groups3,42–44 or designing a through-space CT framework45,46 can to some extent shift the emission peaks to the short-wavelength region, but the corresponding electroluminescence (EL) efficiencies are often unsatisfactory. Therefore, modulating the torsion angles of proper D and A groups could be a promising strategy to explore high-efficiency deep-blue and pure-blue TADF molecules. As a proof of concept, we wish to report an effective design of blue luminescent molecules based on a xanthenone (XT) acceptor and two carbazole (Cz) donors (Figure 1a–c). XT is selected as electron acceptor because of its relatively weak electron-withdrawing nature, high structural rigidity, and ability to promote RISC by enlarging SOC stemming from the n−π* transition of the carbonyl group.40 A previous study demonstrated the ability to tune the color of blue TADF emitters by the introduction of methyl substituents.47 Here, the torsion angles between XT and Cz are tuned progressively by introducing methyl groups at the 1 and 8 positions of Cz, and the strength of the D–A interaction is further optimized by modification at the 3 and 6 positions of Cz with electron-donating tert-butyl groups. We found that the ICT effect is weakened sequentially as the torsion angles between XT and Cz diminishes, gradually blueshifting the emissions from 2MCz-XT to MCz-XT and then to Cz-XT. The introduction of tert-butyl groups can enhance the ICT effect, leading to moderately redshifted emission of 2TBCz-XT relative to Cz-XT. Meanwhile, all these molecules exhibit apparent delayed fluorescence, while the lifetimes of the delayed fluorescence are closely associated with the torsion angles and the strength of the ICT effect. By adopting these new molecules as emitters, highly efficient deep-blue, pure-blue, and sky-blue OLEDs with EL peaks at 442, 462, and 482 nm and outstanding maximum external quantum efficiencies (ηext,maxs) of 22.2%, 33.7%, and 32.1%, respectively, are obtained. These impressive EL performances demonstrate the significance of modulating torsion angles in the design of blue TADF emitters. Figure 1 | (a) Molecular design strategy. (b) Chemical structures of the new molecules with calculated torsion angles and (c) crystal structures of Cz-XT and 2MCz-XT with observed torsion angles. (d) Distributions of HOMOs and LUMOs and the calculated energy splits (ΔESTs) of the new molecules. Download figure Download PowerPoint Results and Discussion The target molecules Cz-XT, MCz-XT, 2MCz-XT, and 2TBCz-XT were facilely synthesized in good yields by palladium-catalyzed Buchwald–Hartwig C–N coupling reactions of 3,6-dibromoxanthen-9-one with Cz and Cz derivatives ( Supporting Information Scheme S1). The molecular structures were characterized by 1H NMR and 13C NMR ( Supporting Information Figures S1–S4) and high-resolution mass spectrometry with satisfactory results. They are thermally and morphologically stable with high decomposition temperatures of 397–459 °C and high glass-transition temperatures over 210 °C, as determined by thermogravimetry analysis and differential scanning calorimetry measurements, respectively ( Supporting Information Figure S5). Their electrochemical properties were measured by cyclic voltammetry using ferrocene as the calibration compound ( Supporting Information Figure S6). The experimental HOMO and LUMO energy levels of Cz-XT, MCz-XT, 2MCz-XT, and 2TBCz-XT are calculated to be −5.69 and −2.92; −5.66 and−2.93; −5.56 and −2.94; and −5.60 and −2.92 eV, respectively. Single crystals of Cz-XT and 2MCz-XT were obtained from a mixture of n-hexane and dichloromethane via slow solvent evaporation. Single-crystal X-ray crystallography analysis reveals that 2MCz-XT adopts a highly twisted D–A connection with large torsion angles of 83° and 91°, due to the severe steric hindrance imposed by the two methyl groups at the 1 and 8 positions of Cz. In contrast, Cz-XT shows a more planar molecular conformation, in which the torsion angles are decreased to 37° and 40°, indicating Cz-XT has a better π-conjugation between Cz and XT than 2MCz-XT. The optimized structures and molecular orbitals of these new molecules were calculated employing a density functional theory (DFT) method.48 As depicted in Figure 1d and Supporting Information Figure S7, the optimized geometry of 2MCz-XT has a similar highly twisted conformation to its crystal structure, with large torsion angles of 83°–84° between XT and Cz. However, MCz-XT and Cz-XT show gradually decreased torsion angles of 70° and 51°–52° due to the reduced steric hindrance. Similar molecular geometry is simulated for 2TBCz-XT compared with Cz-XT. The electron clouds of the HOMOs and LUMOs of these molecules are primarily distributed on Cz and XT, respectively. Due to the highly twisted molecular geometry, 2MCz-XT has the highest degree of separation between the HOMO and LUMO, which leads to the smallest ΔEST of 0.01 eV. The ΔEST of MCz-XT is increased to 0.12 eV due to decreased torsion angles. Cz-XT and 2TBCz-XT have overlapping HOMOs and LUMOs because of the relatively planar conformation. Thus, they have much larger ΔESTs of 0.23 and 0.21 eV than 2MCz-XT and MCz-XT. As displayed in Figure 2a, Cz-XT and 2TBCz-XT have strong absorption maxima at 365 and 384 nm in tetrahydrofuran (THF) solution, which are mainly comprised of the π–π* transitions. MCz-XT and 2MCz-XT have relatively weak absorption maxima at 362 and 368 nm, associated with the ICT states. 2MCz-XT exhibits a green photoluminescence (PL) peak located at 501 nm in THF solution, whereas the PL peaks are blueshifted progressively to 481 nm for MCz-XT and 459 nm for Cz-XT (Figure 2b) due to the weakened ICT effect. The PL peak of 2TBCz-XT is redshifted to 481 nm, which is ascribed to the strengthened ICT effect due to the presence of the tert-butyl groups. To evaluate the ICT effect, the PL spectra of the four molecules in various solvents are tested ( Supporting Information Figure S8). The spectral displacements gradually increase from Cz-XT (60 nm) to MCz-XT (63 nm) and then to 2MCz-XT (71 nm), in good agreement with the increased dihedral angles and strengthened ICT effect. 2TBCz-XT exhibits a larger spectral displacement of 70 nm than Cz-XT (60 nm) because of a stronger ICT effect. These solvation effects further validate that both enlarging D–A dihedral angles and introducing electron-donating groups strengthen the ICT effect of the molecules. When doped in (diphenylphosphoryl)-dibenzo[b,d]-furan (PPF) host at a concentration of 15 wt %, Cz-XT shows a PL peak at 459 nm, similar to that in THF solution, whereas MCz-XT and 2MCz-XT have redshifted PL peaks at 466 and 483 nm, respectively. The PL peak of 2TBCz-XT is located at 468 nm, which is redshifted by 9 nm compared with that of Cz-XT. The photoluminescence quantum yields (ΦPLs) of these molecules in doped films are in the range of 85–94%, higher than those in THF solution (Table 1). The molecular motions are active in solution, largely dissipating the excited-state energy and thus leading to low ΦPL values. But in the doped films, the intramolecular motions of the molecules are greatly suppressed so that the nonradiative dissipation pathways are blocked, accounting for the significantly improved ΦPL values.16,35 Figure 2 | (a) Absorption and (b) photoluminescence (PL) spectra of the new luminogens in THF solutions (10−5 M) and in doped films with a doping concentration of 15 wt % in PPF. Temperature-dependent transient PL decay spectra of (c) Cz-XT, (d) MCz-XT, (e) 2MCz-XT, and (f) 2TBCz-XT doped in PPF host with a doping concentration of 15 wt %, measured under nitrogen. Download figure Download PowerPoint Table 1 | Photophysical Properties of the New Molecules Solutiona Doped Filmb λabs (nm) λem (nm) ΦPLc (%) λem (nm) ΦPLc (%) τdelayedd (μs) Rdelayede (%) kFf (×107 s−1) kICg (×107 s−1) kRISCh (×105 s−1) ΔESTi (eV) Cz-XT 365 459 47 459 85 27.6 64 9.9 1.7 1.0 0.15 MCz-XT 362 481 52 466 86 11.3 51 7.0 1.1 1.8 0.04 2MCz-XT 368 501 47 483 91 1.0 60 1.1 0.1 25.0 0.01 2TBCz-XT 384 481 71 468 94 17.0 50 12.4 0.8 1.2 0.10 aMeasured in THF solution (10−5 M) at room temperature. bVacuum-deposited on a quartz substrate with a doping concentration of 15 wt % in PPF. cPhotoluminescence quantum yield (ΦPL) determined by a calibrated integrating sphere under nitrogen at room temperature. dDelayed fluorescence lifetime (τdelayed) evaluated at 300 K under nitrogen. eRatio of delayed component. fFluorescence decay rate. g Internal conversion decay rate from S1 to S0. hRate constant of RISC process. iEstimated from the high-energy onsets of fluorescence and phosphorescence spectra at 77 K. From the onsets of fluorescence and phosphorescence spectra of doped films ( Supporting Information Figure S9), the experimental ΔESTs of these molecules are calculated to be 0.01–0.15 eV, which are small enough to ensure the occurrence of RISC and thus delayed fluorescence (Figure 2c–f). By progressively reducing the torsion angles between Cz and XT, the ΔEST increases from 0.01 eV of 2MCz-XT to 0.04 eV of MCz-XT and to 0.15 eV of Cz-XT. The ΔEST of 2TBCz-XT is 0.10 eV, smaller than that of Cz-XT, although both molecules adopt nearly identical molecular conformations. These results demonstrate that enlarging the torsion angles and strengthening the ICT effect between D–A groups are conducive to achieving a small ΔEST. Because of the smaller ΔEST, 2MCz-XT exhibits a shorter delayed-fluorescence lifetime (τdelayed) of 1.0 μs and faster RISC, rate constant (kRISC) of 2.5 × 106 s−1, than Cz-XT (27.6 μs, 1.0 × 105 s−1) and MCz-XT (11.3 μs, 1.8 × 105 s−1). Compared with Cz-XT, 2TBCz-XT displays faster RISC, corresponding to a shorter τdelayed of 17.0 μs and a larger kRISC of 1.2 × 105 s−1 (Table 1). The temperature-dependent transient PL decay spectra indicate that Cz-XT and 2TBCz-XT have greatly promoted RISC with apparently enhanced delayed components (Rdelayeds) at high temperatures ( Supporting Information Table S1). However, the change in delayed fluorescence of 2MCz-XT by increasing temperature is obviously diminished, and its τdelayed and Rdelayed vary slightly from 77 to 300 K. These results manifest that the very small ΔEST allows 2MCz-XT to enjoy fast RISC even at low temperatures, while the large ΔESTs make Cz-XT and 2TBCz-XT more dependent on the thermal activation for sufficient RISC. The energy levels of Cz-based donors, XT acceptor, and the new molecules are measured from the phosphorescence spectra and shown in Supporting Information Figure S10. Generally, the locally excited triplet (3LE) energy levels of the donors are close to the 1CT states of MCz-XT, 2MCz-XT, and 2TBCz-XT, whereas the 3LE energy level of XT is close to the 1CT state of Cz-XT. For 2MCz-XT, the 3LE energy level of the donor is close to both 1CT and 3CT states, which may contribute to the fastest RISC and most efficient delayed fluorescence.49 Furthermore, the time-dependent DFT method is employed to gain insights into the RISC in these blue molecules. The natural transition orbital analysis reveals that the S1 and T1 states of the four molecules are dominated by CT transition, whereas the second triplet excited (T2) states are energetically close to the T1 states with LE transition characteristics ( Supporting Information Figures S11 and S12). The different transition natures of S1 and T2 are favorable for RISC.50,51 Furthermore, the calculated SOC matrix elements are also considerable between S1 and T2. These results suggest T2 is involved in RISC and facilitates the occurrence of delayed fluorescence in these molecules, which could be important for Cz-XT and 2TBCz-XT, who have small torsion angles and relatively large ΔESTs. To evaluate the EL performances of these blue molecules, doped OLEDs are fabricated with the configuration of indium tin oxide (ITO)/hexaazatriphenylenehexacabonitrile (HATCN) (5 nm)/1,10-bis(di-4-tolylaminophenyl)cyclohexane (TAPC) (50 nm)/tris[4-(carbazol-9-yl)phenyl]amine (TcTa) (5 nm)/1,3-di(carbazol-9-yl)benzene (mCP) (5 nm)/emitting layer (EML) (20 nm)/PPF or diphenyl-4-triphenylsilylphenyl-phosphine oxide (DPEPO) (5 nm)/3,3′-[5′-[3-(3-pyridinyl)phenyl][1,1′:3′,1″-terphenyl]-3,3″-diyl]bispyridine (TmPyPB) (30 nm)/lithium fluoride (LiF) (1 nm)/Al (Figure 3a–d), where the doped films of these molecules in PPF or DPEPO hosts with varied doping concentrations of 10, 15, and 20 wt % work as EMLs, HATCN and LiF serve as hole- and electron-injection layers, respectively, TAPC and TmPyPB perform as hole- and electron-transporting layers, respectively, TcTa serves as electron-blocking layer, PPF and DPEPO work as hole-blocking layers, and mCP functions as exciton-blocking layer. The key performance data of all the devices with corresponding configurations are summarized in Supporting Information Figures S13–S20 and Tables S2–S5. In general, these devices turn on at low voltages of 2.7–3.6 V and radiate strong light in deep-blue to sky-blue regions. In comparison with Cz-XT, MCz-XT and 2MCz-XT exhibit apparently redshifted EL emissions, and 2TBCz-XT shows redder EL emission than Cz-XT (Table 2). These EL behaviors are consistent with their PL behaviors. Cz-XT and MCz-XT have better EL efficiencies in the DPEPO host, whereas 2MCz-XT and 2TBCz-XT give better EL efficiencies in the PPF host. Whether in PPF or DPEPO, the EL spectra remain stable with minor redshifts less than 8 nm, but the maximum luminance (Lmax) is enhanced greatly by increasing doping concentrations from 10 to 20 wt %. Figure 3 | (a) Energy level diagram and chemical structures of the functional layers. (b) EL spectra at 4 V. (c) Plots of luminance–voltage–current density and (d) external quantum efficiency–luminance of the OLEDs based on the new luminogens. EML, doped films of the new molecules in PPF or DPEPO hosts. Download figure Download PowerPoint Table 2 | EL Performances of the Doped OLEDs Based on the New Molecules Emitter Von (V) ηC (cd A−1) ηP (lm W−1) ηext (%) Lmax (cd m−2) CIE (x, y) λEL (nm) Maximum Value/at 100/at 500 cd m−2 Cz-XT 3.5 15.9/10.3/5.8 13.9/7.5/3.5 22.2/14.4/8.0 1989 (0.15, 0.08) 442 MCz-XT 3.5 29.7/26.4/21.6 25.9/19.3/13.8 24.0/21.3/17.5 5751 (0.15, 0.15) 460 2MCz-XT 3.0 64.4/57.6/53.3 65.2/47.6/38.9 32.1/28.7/26.6 42250 (0.17, 0.30) 482 2TBCz-XT 2.9 47.9/38.6/31.9 50.2/33.7/24.5 33.7/27.1/22.4 20370 (0.15, 0.18) 462 Abbreviations:Von, turn-on voltage at 1 cd m−2; ηC, current efficiency; ηP, power efficiency; ηext, external quantum efficiency; Lmax, maximum luminance; CIE, Commission Internationale de I'Eclairage coordinates; λEL,EL peak. Cz-XT radiates deep blue-light with an EL peak at 442 nm, Commission Internationale de l'Eclairage (CIE) color coordinates of (0.15, 0.08), and an Lmax of 1989 cd m−2 in DPEPO host at a doping concentration of 10 wt %. The full width at half maxima value of the EL spectrum is 63 nm, similar to that of the PL spectrum (64 nm). The maximum current efficiency (ηC,max), maximum power efficiency (ηP,max), and ηext,max are 15.9 cd A−1, 13.9 lm W−1, and 22.2%, respectively. More importantly, 2TBCz-XT shows pure-blue light with an EL peak at 462 nm (CIEx,y = 0.15, 0.18) and a Lmax of 20370 cd m−2 in PPF host at a doping concentration of 20 wt %. The ηC,max, ηP,max, and ηext,max are 47.9 cd A−1, 50.2 lm W−1, and 33.7%, respectively. The device comprised of 2MCz-XT in PPF host at a doping concentration of 10 wt % displays sky-blue light with an EL peak at 482 nm (CIEx,y = 0.17, 0.30) and provides an ηext,max of 32.1% similar to that of 2TBCz-XT ( Supporting Information Tables S2–S5). In addition to the efficient RISC that ensures nearly full exciton utilization and excellent ΦPLs of 91% (2MCz-XT) and 94% (2TBCz-XT), the high horizontal orientation ratios of 78.0% and 84.0% of 2MCz-XT and 2TBCz-XT (Figure 4a,b), respectively, account for the outstanding ηext,maxs exceeding 30%.7,24,25,34,35,52,53 To the best of our knowledge, these impressive ηext,maxs demonstrate Cz-XT and 2TBCz-XT are among the currently reported state-of-the-art deep-blue and pure-blue TADF materials ( Supporting Information Table S6). Figure 4 | PL of (a) 2MCz-XT and (b) 2TBCz-XT in doped Download figure Download PowerPoint TADF molecules are in highly twisted D–A structures, which to efficient blue emissions because of a strong ICT effect. To this we a and effective strategy of modulating torsion angles of D–A groups for the of efficient blue delayed-fluorescence materials, based on a of deep-blue and pure-blue luminescent molecules consisting of Cz donor and XT By gradually decreasing the torsion the PL peak of Cz-XT is apparently blueshifted relative to those of MCz-XT and 2MCz-XT, accompanied by increased ΔEST and elongated By the electron-donating ability of Cz via the introduction of tert-butyl 2TBCz-XT shows a moderately redshifted PL and its ΔEST and τdelayed smaller and respectively, in comparison with Cz-XT. Although Cz-XT and 2TBCz-XT have more planar structures and larger they strong deep-blue and pure-blue delayed fluorescence in doped films with excellent ΦPLs of and respectively. The EL emissions of these molecules the as the PL emissions, thus achieving blue high-performance The device using Cz-XT as radiates deep-blue light with an EL peak at 442 nm (CIEx,y = 0.15, 0.08) and a high ηext,max of more efficient OLEDs are achieved by adopting 2TBCz-XT and 2MCz-XT as emitters, providing pure-blue and sky-blue light peaking at 462 nm (CIEx,y = 0.15, 0.18) and 482 nm (CIEx,y = 0.17, 0.30) with outstanding ηext,maxs of and 32.1%, respectively. These OLEDs are among the current state-of-the-art TADF OLEDs with similar which may the of efficient blue organic luminescent materials by of D–A torsion Supporting Information Supporting Information is and and fabrication and crystal data of Cz-XT and 2MCz-XT, analysis and differential scanning calorimetry cyclic transient PL decay fluorescence and phosphorescence and device performance of The of study is by the Science of China the Science of Guangdong and the State Key of Luminescent Materials and Devices, South China University of TADF Emitter and Efficient and Doped OLEDs with Wu Chen Ma Zhao Tang OLEDs with and by a of Efficient Materials for Blue Organic Efficient in Organic Yang Efficient by for Chen Wu of Blue and and Their OLEDs with Efficient Blue Based on and from and Their to Organic for Blue Organic Efficient Blue Based on Single and Organic The Key of Chen Wu for Efficient

Journal of Polymer Science Part A: Polymer ChemistryVolume 34, Issue 9 p. 1815-1818 Rapid Communication Effect of benzylic halides on cationic polymerization of 1,3-pentadiene Y. X. Peng, Corresponding Author Y. X. Peng Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, P.O. Box 415, Chengdu 610041, ChinaChengdu Institute of Organic Chemistry, Chinese Academy of Sciences, P.O. Box 415, Chengdu 610041, ChinaSearch for more papers by this authorY. J. Dong, Y. J. Dong Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, P.O. Box 415, Chengdu 610041, ChinaSearch for more papers by this authorJ. L. Liu, J. L. Liu Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, P.O. Box 415, Chengdu 610041, ChinaSearch for more papers by this authorH. S. Dai, H. S. Dai Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, P.O. Box 415, Chengdu 610041, ChinaSearch for more papers by this authorL. F. Cun, L. F. Cun Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, P.O. Box 415, Chengdu 610041, ChinaSearch for more papers by this author Y. X. Peng, Corresponding Author Y. X. Peng Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, P.O. Box 415, Chengdu 610041, ChinaChengdu Institute of Organic Chemistry, Chinese Academy of Sciences, P.O. Box 415, Chengdu 610041, ChinaSearch for more papers by this authorY. J. Dong, Y. J. Dong Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, P.O. Box 415, Chengdu 610041, ChinaSearch for more papers by this authorJ. L. Liu, J. L. Liu Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, P.O. Box 415, Chengdu 610041, ChinaSearch for more papers by this authorH. S. Dai, H. S. Dai Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, P.O. Box 415, Chengdu 610041, ChinaSearch for more papers by this authorL. F. Cun, L. F. Cun Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, P.O. Box 415, Chengdu 610041, ChinaSearch for more papers by this author First published: 15 July 1996 https://doi.org/10.1002/(SICI)1099-0518(19960715)34:9<1815::AID-POLA20>3.0.CO;2-8Citations: 4AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume34, Issue915 July 1996Pages 1815-1818 RelatedInformation

As two pivotal functional segments, triazine and porphyrin can be coupled to form a highly cross-linked conjugated polymer. Although the obtained conjugated polymers are almost insoluble in most so...

Classical Julia–Kocienski fluoroolefination represents an indispensable platform for the construction of monofluoroalkenes. Nevertheless, its complex multistep mechanistic manifold along with the u...

Advanced MaterialsVolume 19, Issue 13 p. 1662-1662 CorrectionFree Access Optical Detection of Mercury(II) in Aqueous Solutions by Using Conjugated Polymers and Label-Free Oligonucleotides This article corrects the following: Optical Detection of Mercury(II) in Aqueous Solutions by Using Conjugated Polymers and Label-Free Oligonucleotides X. Liu, Y. Tang, L. Wang, J. Zhang, S. Song, C. Fan, S. Wang, Volume 19Issue 11Advanced Materials pages: 1471-1474 First Published online: May 9, 2007 X. Liu, X. Liu Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800 (P.R. China)Search for more papers by this authorY. Tang, Y. Tang Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100080 (P.R. China)Search for more papers by this authorL. Wang, L. Wang Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800 (P.R. China)Search for more papers by this authorJ. Zhang, J. Zhang Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800 (P.R. China)Search for more papers by this authorS. Song, S. Song Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800 (P.R. China)Search for more papers by this authorC. Fan, C. Fan fchh@sinap.ac.cn Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800 (P.R. China)Search for more papers by this authorS. Wang, S. Wang wangshu@iccas.ac.cn Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100080 (P.R. China)Search for more papers by this author X. Liu, X. Liu Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800 (P.R. China)Search for more papers by this authorY. Tang, Y. Tang Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100080 (P.R. China)Search for more papers by this authorL. Wang, L. Wang Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800 (P.R. China)Search for more papers by this authorJ. Zhang, J. Zhang Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800 (P.R. China)Search for more papers by this authorS. Song, S. Song Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800 (P.R. China)Search for more papers by this authorC. Fan, C. Fan fchh@sinap.ac.cn Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800 (P.R. China)Search for more papers by this authorS. Wang, S. Wang wangshu@iccas.ac.cn Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100080 (P.R. China)Search for more papers by this author First published: 26 June 2007 https://doi.org/10.1002/adma.200790049Citations: 18AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume19, Issue13July, 2007Pages 1662-1662 RelatedInformation

New Members of the Editorial Board and International Advisory Board of <i>Angewandte Chemie</i>

Developing a descriptor to understand the reactivity of a catalyst is critical in achieving the rational design of heterogeneous catalysts. Ideally, the descriptor should be simple, predictive, as ...

We are pleased to introduce this Special Issue of Advanced Materials, which showcases the exciting and innovative work carried out at the Tianjin Collaborative Innovation Center of Chemical Science and Engineering (CICCSE). Cushioned in the center of Tianjin—the fourth largest city in China—the CICCSE is a joint research center hosted by Tianjin University (TJU) and Nankai University (NKU). TJU is recognized as the first modern higher education institution in China, established in 1895 as Imperial Tientsin University and later Peiyang University. In 1951, upon restructuring, the University was re-named Tianjin University and has since become one of the largest multidisciplinary engineering universities in China. Coincidentally, this year TJU will be celebrating her 120th anniversary. NKU was founded as a private institution in 1919 by prominent educators Zhang Boling and Yan Fansun and is one of the most prestigious universities in China. The CICCSE serves as the nationwide home for collaborative research in materials science and engineering, chemical science and engineering, physics, and other related disciplines. The establishment of the CICCSE was initialized by the two universities in 2011 and was formally approved and financially supported (ca. $8M per year) by the Ministry of Education on April 4th, 2013. The CICCSE is constructed with the combination of the core disciplines of chemistry of Nankai University and chemical engineering and materials science of Tianjin University. The Institute of Process Engineering of Chinese Academy of Sciences, the Sinopec Group, and the Tianjin Bohai Chemical Group are also core members of the CICCSE. The Center's missions are to discover and characterize new materials that involve the interactions with light, electricity, and heat at the molecular scale, and to scale up the synthetic processes based on the successful employment of unit operations and chemical-engineering fundamentals for efficient conversion of energy and resources for the national steady growth of economy. The goals of the CICCSE are also to provide opportunities for young researchers to develop the skills needed to excel in a global research environment; and to integrate materials/chemical research experiences with an awareness of environmental, health, and energy issues into the undergraduate and graduate curricula. The Center's research program is highly cross-disciplinary and is organized into five platforms including: i) catalytic materials and processes for efficient conversion of syngas and CO2; ii) photoelectric conversion and energy-storage science and technology; iii) design, synthesis, and applications of artificial biomaterials; iv) the structural effect of functional materials; and v) invention and conversion of chiral materials. These platforms currently contain 32 teams with around 200 faculty and staff members and approximately 1700 graduate students; each team has extensive expertise in materials/chemical synthesis, characterization, theoretical modeling, and device design and fabrication. These collaborative teams also comprise joint faculty members from multiple institutions including Tsinghua University, Peking University, the University of Science and Technology of China, Lanzhou University, the Chinese Academy of Sciences, etc. This special issue contains 2 Progress Reports, 4 Reviews, and 9 Research News articles. These contributions indicate that the materials research is deeply embedded in the majority of Science and Engineering Departments throughout the campus of TJU and NKU. The authors are primarily from the School of Chemical Engineering and Technology (TJU), the School of Chemistry (NKU), the School of Materials Science and Engineering (TJU), the College of Sciences (TJU), and the School of Physics (NKU). Particularly, a young generation of investigators has also emerged, who inherit the ideals and goals of the center. In the area of supramolecular materials, Prof. Yu Liu and co-workers present the construction and functions of cyclodextrin-based one-dimensional supramolecular strands and their secondary assemblies. Prof. Wen-Ping Hu and his group introduce surfactant-assisted self-assembly of supramolecular porphyrin with 1D structures. In the area of carbon-based materials, Prof. Yongsheng Chen leads the discussion of graphene-based materials for lithium-ion hybrid supercapacitors. Prof. Xiaobin Fan and co-workers overview graphene-based binder-free electrodes for high-performance energy storage. Prof. Quan-Hong Yang and co-workers discuss the synthesis and ion transport properties of 2D porous carbons. Prof. Naiqin Zhao and co-workers demonstrate the employment of in situ synthesis of carbon nanotubes and graphene-reinforced composites for structural materials and electrochemical applications. A number of papers are also presented regarding advances in porous materials. Prof. Xianhe Bu and co-workers summarize recent advances and applications of flexible metal–organic frameworks (MOFs). Prof. Xun Wang and co-workers provide an introduction of well-defined MOF hollow nanostructures for gas-phase catalytic reactions. Prof. Zhongyi Jiang and co-workers report on the recent development of nanostructured ion-exchange membranes for fuel cells. In the field of photoelectric conversion and energy-storage materials, Prof. Jun Chen and co-workers discuss a number of functional cathode materials for sodium-ion batteries. Prof. Shizhang Qiao and co-workers describe the fundamentality and functionality regarding the engineering of advanced electrocatalysts for energy conversion. Prof. Ji-Jun Zou and co-workers review the utilization of tungsten oxides for photocatalysis, electrochemistry, and phototherapy applications. Prof. Jinlong Gong and co-workers provide mechanistic understandings of the plasmonic enhancement effect for solar water splitting. In the field of metallic materials, Prof. Xiwen Du and co-workers introduce the synthesis, characterization, and applications of freestanding ultrathin metallic nanosheets. Prof. Jianguo Tian and co-workers discuss the emergent functionality and controllability in few-layer metasurfaces. The Guest Editors would like to thank all the authors for their excellent contributions and the referees for their dedication and responsibility. We are indebted to Prof. Jiannian Yao (the Director of CICCSE) and Prof. Yaqing Feng (the Deputy Director of CICCSE), as well as other administrative members of staff for their constant encouragement and support. We are also happy to acknowledge Dr. Peter Gregory, Dr. Duoduo Liang, and Dr. Yan Li for their great support, excellent suggestions, and kind cooperation. Our gratitude also goes to the whole editorial team of Advanced Materials for their enthusiastic pushing forward and professional editing. We want to express appreciation for the efforts of our colleagues at the TJU and NKU, who involve the production of this special issue. Funding and support for this issue has been provided through the CICCSE, the School of Chemical Engineering and Technology at TJU, and the College of Chemistry at NKU. Jinlong Gong is a professor in the School of Chemical Engineering and Technology at Tianjin University and a Principle Investigator at CICCSE. He obtained his B.Sc. degree at Tianjin University and his Ph.D. at the University of Texas at Austin under the direction of Buddie Mullins. Upon the completion of postdoctoral training with Professor George M. Whitesides at Harvard University, he joined the faculty of Tianjin University. His research interests in catalytic materials include conversions of green energy, novel utilization of carbon oxides, and synthesis and applications of optoelectronic materials. Jun Chen is a professor in the College of Chemistry at Nankai University and a Principle Investigator at CICCSE. He obtained his B.Sc. and M.Sc. degrees from Nankai University in 1989 and 1992, respectively, and his Ph.D. from Wollongong University (Australia) in 1999. He held the NEDO fellowship at the National Institute of AIST Kansai Center (Japan) from 1999 to 2002. He was appointed as the chair professor of energy-materials chemistry at Nankai University in 2002, the outstanding young scientist from NSFC in 2003, the Cheung Kong Scholar from Ministry of Education in 2005, the chief scientist of the National Nano Key Science Research from Ministry of Science & Technology in 2010. His research expertise is energy-storage and conversion with batteries, fuel cells, and solar cells. Naiqin Zhao is a professor in the School of Materials Science and Engineering at Tianjin University and the Director of the Tianjin Key Laboratory of Composite and Functional Materials. She obtained her B.Sc. and Ph.D. at Tianjin University. She was a visiting scholar at Illinois Institute of Technology and The Hong Kong Polytechnic University; and a visiting professor at Tohoku University and Vanderbilt University. Her research interests focus on phase transformation and properties of alloys and composites, and the synthesis and characteristics of the carbon nanophase and its composites. Yu Liu is a professor in the College of Chemistry at Nankai University and a Principle Investigator at CICCSE. He graduated from the University of Science and Technology of China in 1977, and received his Ph.D. from the Himeji Institute of Technology, Japan, in 1991. Then, he was a postdoctoral fellow at the Lanzhou Institute of Chemical Physics. In 1993, he moved to Nankai University as a full professor. He is the chairman of the Asian and Oceanian Cyclodextrin League, a member of the International Cyclodextrin Advisory Committee, and a specially-appointed professor of “Cheung Kong Scholars Programme of China”. His research interests focus on organic supramolecular chemistry.

Catalytic [2+2+2] Tandem Cyclization with Alkyl Substituted Methylene Malonate Enabling Concise Total Synthesis of Four Malagasy Alkaloids

Open AccessCCS ChemistryCOMMUNICATIONS2 Sep 2022Phosphonium-Based Ionic Thermally Activated Delayed Fluorescence Emitters for High-Performance Partially Solution-Processed Organic Light-Emitting Diodes Xu-Lin Chen, Xiao-Dong Tao, Ya-Shu Wang, Zhuangzhuang Wei, Lingyi Meng, Dong-Hai Zhang, Fu-Lin Lin and Can-Zhong Lu Xu-Lin Chen State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials, Xiamen Institute of Rare Earth Materials, Haixi Institutes, Chinese Academy of Sciences, Xiamen, Fujian 361021 Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China, Fuzhou, Fujian 350108 , Xiao-Dong Tao State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials, Xiamen Institute of Rare Earth Materials, Haixi Institutes, Chinese Academy of Sciences, Xiamen, Fujian 361021 , Ya-Shu Wang State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials, Xiamen Institute of Rare Earth Materials, Haixi Institutes, Chinese Academy of Sciences, Xiamen, Fujian 361021 , Zhuangzhuang Wei State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials, Xiamen Institute of Rare Earth Materials, Haixi Institutes, Chinese Academy of Sciences, Xiamen, Fujian 361021 , Lingyi Meng State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials, Xiamen Institute of Rare Earth Materials, Haixi Institutes, Chinese Academy of Sciences, Xiamen, Fujian 361021 , Dong-Hai Zhang State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials, Xiamen Institute of Rare Earth Materials, Haixi Institutes, Chinese Academy of Sciences, Xiamen, Fujian 361021 , Fu-Lin Lin State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials, Xiamen Institute of Rare Earth Materials, Haixi Institutes, Chinese Academy of Sciences, Xiamen, Fujian 361021 and Can-Zhong Lu *Corresponding author: E-mail Address: [email protected] State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials, Xiamen Institute of Rare Earth Materials, Haixi Institutes, Chinese Academy of Sciences, Xiamen, Fujian 361021 Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China, Fuzhou, Fujian 350108 https://doi.org/10.31635/ccschem.022.202202145 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Ionic thermally activated delayed fluorescence (TADF) emitters are rarely investigated due to their poor photoluminescence and electroluminescence performance. Herein, highly efficient ionic TADF emitters with charged donor–acceptor (D–A+) and D–A+–D architectures are designed, innovatively based on the phosphonium cation electron acceptor. The symmetric D–A+–D compound in doped film exhibits a high photoluminescence quantum yield of 0.91 and a short emission lifetime of 1.43 microseconds. Partially solution-processed organic light-emitting diodes based on these ionic TADF emitters achieve a maximum external quantum efficiency (EQE) of 18.3% and a peak luminance of 14,532 candelas per square meter (cd/m2) and show a small efficiency roll-off of 7.1% (EQE = 17%) at a practical high luminance of 1000 cd/m2. These results demonstrate the high potential of phosphonium cations as promising electron acceptors to construct TADF emitters for high-performance electroluminescence devices. The current study opens up an appealing way for future exploitation of high-efficiency ionic TADF materials. Download figure Download PowerPoint Introduction Thermally activated delayed fluorescence (TADF) molecules have been developed as third-generation organic light-emitting diode (OLED) emitters, owing to their potential to realize an internal quantum efficiency of unity without using noble metals.1,2 While numerous highly efficient TADF-based OLEDs have been reported to date, some key challenges remain to be tackled for practical applications.3 For example, TADF-OLEDs usually suffer from severe efficiency roll-off during high-luminance operations owing to exciton annihilation.4–6 To prevent the formation of high-energy excitons and reduce efficiency roll-off in OLEDs, efficient TADF emitters with short emission lifetimes7–10 and fast reverse intersystem crossing (RISC)11–14 are highly desired. TADF emitters are generally composed of suitable electron-donor (D) and electron-acceptor (A) moieties that can create spatial separation of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). Finding the ideal D and A species is the priority in order to exploit TADF molecules. Unlike electron donors that are almost limited to arylamine derivatives,15 a wide variety of electron acceptors based on main-group elements have been utilized to construct TADF emitters,16 including arylboron,17–22N-heterocycle,23–26 cyano,1,27,28 sulfone,29 carbonyl30–35 groups, and so on. To date, the vast majority of TADF materials are constructed based on neutral D and A moieties ( Supporting Information Figure S5). Charged luminescent materials (e.g., cyanines, rhodamines, ionic metal complexes, etc.) have been utilized in versatile photonic applications due to their ionic nature, diverse photophysical properties, and unique solubility. For instance, many ionic organic dyes have been ultilized as chemosensors in living systems because of their excellent photophysical properties, appreciable water solubility, and biocompatibility.36,37 Ionic transition metal complexes have been employed as emitters in light-emitting electrochemical cells.38 Ionic luminescent compounds are often overlooked in OLED applications, owing to their poor photoluminescence/electroluminescence (PL/EL) properties and inability to be processed via vacuum deposition. However, their intrinsic ionic nature and unique solubility may offer possibilities for developing multilayer solution-processed OLEDs. Recently, a few ionic TADF materials39–47 containing anion/cation moieties or D/A ion-pairs have revealed their potential for PL and EL applications. Nevertheless, it remains a formidable challenge to realize high-performance OLEDs based on ionic TADF emitters ( Supporting Information Table S8). Owing to its 3s23p3 valence shell, phosphorus favors valences ranging from 3 to 5 in organophosphorus compounds. The lone-pair electrons can make trivalent phosphorus atoms act as a donor in organophosphorus molecules, but oxidation to pentavalent phosphine oxide or arylation/alkylation to tetravalent phosphonium cations drastically changes its properties to a typical electron acceptor. Compared with phosphine oxide, which has usually been employed as a weak electron-deficient unit to build n-type and ambipolar host materials for OLEDs,48,49 the phosphonium cation is a noticeably stronger electron acceptor,50,51 offering appealing opportunities to yield visible-light emitters with strong intramolecular charge-transfer (ICT) character. For example, Koshevoy and coworkers52,53 recently reported the unique PL behaviors in solvents of a series of D–π–A fluorophores containing phosphonium cation acceptors. Inspired by the intrinsic electron-deficient property of phosphonium cations, we have selected tetraphenylphosphonium cation as acceptor and designed two ionic TADF materials, namely DMAC-TPP[PF6] and 2DMAC-TPP[PF6] (Figure 1a). These emitters exhibit efficient TADF in doped films with high photoluminescence quantum yields (PLQYs) and short emission lifetimes. Partially solution-processed OLEDs based on these emitters achieve high external quantum efficiencies (EQEs) with only minor efficiency roll-off, demonstrating the high potential of phosphonium cation electron acceptors for the construction of high-performance ionic TADF materials. Figure 1 | (a) Chemical structures; (b) frontier orbital distributions (left: DMAC-TPP[PF6]; right: DMAC-TPP[PF6]); (c) crystal structure (DMAC-TPP[PF6]). Download figure Download PowerPoint Results and Discussion The electronic properties of these compounds were investigated by density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations at the M06-2X/6-311G(d,p) level. As shown in Figure 1b, each compound shows spatially separated frontier molecular orbitals, with the HOMO predominantly distributed over the acridinyl unit and the LUMO mainly located on the remainder of the molecule. The TD-DFT calculations predict that the S1 and T1 states are characterized by HOMO–LUMO ICT transitions Supporting Information Figure S1, with S1–T1 energy difference (ΔEST) of 0.07 eV for DMAC-TPP[PF6] and 0.01 eV for 2DMAC-TPP[PF6], respectively. Owing to the symmetrical molecular structure, the excited states of 2DMAC-TPP[PF6] appear in pairs degenerately (S1/S2, T1/T2, T3/T4, etc.). The calculated energy levels of excited states and spin–orbit coupling (SOC) constants are summarized in Supporting Information Table S1. For 2DMAC-TPP[PF6], the total SOC between S1/S2 and T1/T2 states which have dominant CT exciton characters was calculated to be 0.145 cm−1, while the calculated SOC between S1/S2 and higher-lying triplet states, namely T3/T4 and T5/T6, reach up to 3.807 and 4.021 cm−1, respectively. The same situation exists in the case of DMAC-TPP[PF6] with SOCS1–T1, SOCS1–T2, and SOCS1–T3 of 0.270, 1.946, and 1.171 cm−1, respectively. The first-order mixing coefficient between singlet and triplet states is proportional to their spin–orbit interaction and inversely proportional to the energy gap between them.2 Considering the large energy gaps (over 0.5 eV) between the higher-lying triplet states and S1 states, we speculate that the small ΔEST rather than the higher-lying triplet states play a key role in spin-flip conversion between the S1 and T1 states. These tetraarylphosphonium salts were synthesized in high yields via nickel-catalyzed coupling reactions52,54 between triarylphosphines and aryl bromides and the subsequent anion-exchange reactions (see Supporting Information for details). These compounds are quite air stable in the solid state as well as in solution. The powders survive in ambient conditions without decomposition over at least several months. As depicted in Supporting Information Figure S2, DMAC-TPP[PF6] and 2DMAC-TPP[PF6] show excellent thermal stability with high decomposition temperatures (Td, 5% weight loss) of 399 and 394 °C, respectively. Atomic-force microscopy (AFM) images ( Supporting Information Figure S3) reveal that the spin-coated doped films of these materials (30 wt % in PYD2, the same as the OLED-emitting layers) show fairly smooth surfaces with small root-mean-square surface roughness (Rq) values of 0.246 and 0.256 nm for DMAC-TPP[PF6] and 2DMAC-TPP[PF6], respectively. The excellent thermal stability and high-quality film morphologies support EL device fabrication via solution processes. The crystal structure of DMAC-TPP[PF6] (Figure 1c) reveals that the phosphorus atom (sp3-hybridization) adopts tetrahedral geometry with tetrahedral angles of approximately 109°. The cationic moiety exhibits nearly perpendicular D–A linkage with a dihedral angle of 81.4°, which can result in spatially well-separated frontier molecular orbitals and small ΔEST. Moreover, there exist significant intramolecular (Figure 1c) and intermolecular interactions ( Supporting Information Figure S4) in the lattice, which are expected not only to suppress nonradiative deactivation by rigidifying molecular conformation but also to facilitate the formation of high-quality thin films.55,56 The photophysical properties of these emitters were investigated in dichloromethane and 30 wt %-doped polymethyl methacrylate (PMMA) films. Both compounds exhibit similar absorption profiles, composed of two types of absorption bands (Figure 2a). The intense absorptions below 370 nm are assigned to the π–π* transition originating from the donor moieties while the much weaker absorption bands between 370 and 460 nm are attributed to the ICT transitions from the DMAC donor(s) to the tetraphenylphosphonium acceptor. From the onset of absorption spectra ( Supporting Information Figure S5), optical bandgaps (Eg) were calculated to be 2.76 and 2.74 eV for DMAC-TPP[PF6] and 2DMAC-TPP[PF6], respectively. The increased number of donors results in slightly red-shifted absorption bands. These compounds exhibit strong yellow emission (λmax = 563 and 567 nm, respectively) in degassed dichloromethane at room temperature. The broad and structureless PL spectra as well as their solvent-polarity-dependent behaviors ( Supporting Information Figure S14 and Table S4) confirm CT characteristics of the emissive states. The transient PL decay curves of the investigated emitters in dichloromethane before and after Ar bubbling were compared to verify the involvement of triplet states in the light-emitting process (Figure 2b). A conspicuous delayed decay with significantly increased intensity was observed after 15 min of Ar bubbling to remove dissolving oxygen which can quench the triplet excited states of emitters. This behavior clearly confirms the contribution of triplet states to the fluorescence processes. Remarkably, the delayed decay components of DMAC-TPP[PF6] and 2DMAC-TPP[PF6] in degassed dichloromethane were fitted with ultrashort single-exponential lifetimes of 600 and 549 ns ( Supporting Information Figures S9 and S10), respectively. Figure 2 | (a) Absorption and PL spectra measured in dichloromethane (c = 2 × 10−5 M) at room temperature; (b) transient PL decay curves in dichloromethane (c = 2 × 10−5 M) before/after Ar bubbling for 15 min at room temperature; (c) transient PL decay curves of 2DMAC-TPP[PF6] in 30 wt %-doped PMMA film at different temperatures; (d) time-resolved PL spectra in the 30 wt %-doped PMMA films at 77 K. Fluo.: fluorescence; Phos.: phosphorescence. The PL measurements were excited at 335 nm. Download figure Download PowerPoint The 30 wt %-doped PMMA films of DMAC-TPP[PF6] and 2DMAC-TPP[PF6] display bluish-green PL with emission maxima of 511 and 514 nm ( Supporting Information Figure S11 and Table 1) and PLQYs of 0.75 and 0.91, respectively. Compared with those recorded in dilute solution, for example, in dichloromethane, ethanol, and acetonitrile ( Supporting Information Figure S14 and Table S4), the PL spectra in 30 wt %-doped PMMA films significantly blue-shift. This behavior probably originates from two contributions. First, the solvation effect on the CT-excited states is considerably weakened in the doped nonpolar polymer films. Second, in the more rigid environment of the polymer films, intramolecular rotations and excited-state distortions are effectively restricted, thereby decreasing the vertical transition energies from the emissive ICT states (S1) to ground state (S0), resulting in significantly blue-shifted PL spectrum maxima. As shown in Figure 2c and Supporting Information Figure S12, temperature dependence of transient PL decay reveals that the intensity ratio of delayed fluorescence to prompt fluorescence increased when temperature was increased from 77 to 300 K. At ambient temperature (300 K), the observed emission originates from the S1 state, which is significantly populated via thermally-activated upconversion from the energetically lower-lying T1 state, demonstrating the TADF process. From onsets of the time-resolved PL spectra (fluorescence and phosphorescence spectra) taken at 77 K (Figure 2d and Supporting Information Figure S6), S1 and T1 energies and ΔEST are estimated to be 2.88, 2.82, and 0.06 eV for DMAC-TPP[PF6] and 2.86, 2.81, and 0.05 eV for 2DMAC-TPP[PF6], respectively. Such small ΔEST values would facilitate rapid upconversion of excitons from T1 to S1 through RISC process.57 At 300 K, the prompt fluorescence lifetimes (τPF) and delayed fluorescence lifetimes (τDF) were measured to be 16.6 ns and 1.67 μs for DMAC-TPP[PF6], and 18.2 ns and 1.43 μs for 2DMAC-TPP[PF6], respectively (see Supporting Information for detailed decay-curve fitting). The emission lifetimes are as short as those of representative phosphorescence Ir(III) complexes.58,59 Based on the PLQY and lifetime data, rate constants of the key photophysical processes were estimated using a previously reported method derived by Tsuchiya et al.60 (see Supporting Information for details). The radiative decay rate constants ( k r S ) from S1 to S0 are nearly the same and exceed 1.7 × 107 s−1 for both compounds, which are much higher than corresponding nonradiative rate constants ( k nr S ) (5.80 × 106 and 1.69 × 106 s−1 for DMAC-TPP[PF6] and 2DMAC-TPP[PF6], respectively). The ISC process of each compound (kISC = 2.75 × 107 s−1 for DMAC-TPP[PF6] and kISC = 3.51 × 107 s−1 for 2DMAC-TPP[PF6]) is much faster than its competitive processes, namely the radiative and nonradiative transition of the S1 state, implying that the initially generated singlet excitons in these compounds are significantly transformed to triplet excitons. Notably, the rate constants of RISC (kRISC) of DMAC-TPP[PF6] and 2DMAC-TPP[PF6] reach up to 1.55 × 106 and 2.05 × 106 s−1, respectively. Fast radiative transition together with fast RISC of these emitters result in efficient utilization of excitons and short exciton lifetimes.61 Table 1 | Photophysical Data of the Invesigated Compounds in 30 wt %-Doped PMMA Films at 300 K Compound λPLa (nm) ΦPLb ΦPF/ΦDFc τPF/τDFd (ns/μs) ES1/ET1/ΔESTe (eV) k r S / k nr S f (106 s−1) kISC/kRISCg (106 s−1) DMAC-TPP[PF6] 511 0.75 0.29/0.46 16.6/1.67 2.88/2.82/0.06 17.5/5.80 27.5/1.55 2DMAC-TPP[PF6] 514 0.91 0.31/0.60 18.2/1.43 2.86/2.81/0.05 17.0/1.69 35.1/2.05 aThe wavelength at PL maximum (excited at 335 nm). bOverall PLQY. cΦPF and ΦDF are the quantum yields of prompt fluorescence and delayed fluorescence, respectively. dτPF and τDF are the lifetimes of prompt fluorescence and delayed fluorescence, respectively. eEnergy levels of S1 and T1 state were estimated from the onsets of time-resolved PL spectra at 77 K ( Supporting Information Figure S6). f k r S and k nr S represent the radiative and nonradiative rate constants of S1 states, respectively. gkISC and kRISC refer to the rate constants of intersystem crossing (ISC) and reverse ISC, respectively. The film thickness of samples was 100 nm. To evaluate EL properties of these emitters, partially solution-processed OLEDs were fabricated with a device structure of indium tin oxide (ITO)│poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) (30 nm)│poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(N-(4-sec-butylphenyl) diphenylamine)] (TFB) (10 nm)│PYD2: emitter (7:3, 40 nm)/m4PO (8 nm)│TPBi (45 nm)│LiF (1 nm)│Al (100 nm) (Figure 3a), where PEDOT:PSS, TFB, m4PO,62 TPBi, and LiF, act as the hole-injection, hole-transporting, hole-blocking, electron-transporting, and electron-injection layers, respectively ( Supporting Information Figure S16). PYD263 was selected as a host material due to its high triplet energy (T1 = 2.93 eV), which is conducive to confining triplet excitons of the investigated greenish-blue emitters (T1 = 2.81–2.82 eV), and due to its proper HOMO and LUMO energies (EHOMO/ELUMO = −5.7 eV/−2.3 eV) which fit the corresponding values of the emitters and adjacent layers for effective carrier transporting. The host–guest ratio was optimized ( Supporting Information Table S7 and Figures S17–S18). The results show that 30 wt % doped devices achieved the best device performance with efficient host to guest energy transfer. The HOMO and LUMO levels of DMAC-TPP[PF6] and 2DMAC-TPP[PF6] were estimated from the oxidation potentials and optical bandgaps ( Supporting Information Figures S15 and Tables S6). EL performances are shown in Figure 3b–d and Table 2. Figure 3 | (a) Energy-level diagram of the OLEDs; (b) current density–voltage–luminance characteristics; (c) EL spectra at various voltages; (d) EQE, current efficiency (CE) and power efficiency (PE) versus luminance characteristics. Download figure Download PowerPoint Table 2 | Summary of Device Performances Device (30 wt %-Doped) λELa (nm) Vonb (V) Lmaxc (cd/m2) EQEd (%) CEe (cd/A) PEf (lm/W) CIE1931g (x, y) DMAC-TPP[PF6] 508 5.0 9496 15.3/13.6/9.9 42.7/37.9/27.6 19.2/10.6/6.0 (0.25, 0.47) 2DMAC-TPP[PF6] 512 4.7 14532 18.3/17.0/13.2 53.4/49.5/38.5 26.0/15.2/9.3 (0.27, 0.49) aThe wavelength at EL maximum (recorded at 12 V). bTurn-on voltage at 1 cd/m2. cMaximum luminance. dEQE maximum value, value at 1000 cd/m2 and value at 5000 cd/m2. eCE maximum value, value at 1000 cd/m2, and value at 5000 cd/m2. fPE maximum value, value at 1000 cd/m2, and value at 5000 cd/m2. gCIE coordinates measured at 12 V. The 30 wt %-doped OLEDs employing DMAC-TPP[PF6] and 2DMAC-TPP[PF6] turned on at approximately 4.7 and 5.0 V, and exhibited bluish-green EL with emission maxima of 508 nm [Commission Internatinale de L'Eclairage (CIE) = 0.25, 0.47] and 512 nm (CIE = 0.27, 0.49), respectively. It is particularly worth mentioning that these devices exhibited perfect emission-color stability over a wide range of operating voltages (Figure 3c). The DMAC-TPP[PF6]- and 2DMAC-TPP[PF6]-based devices showed maximum EQEs of 15.3% and 18.3% and peak luminances of 9496 and 14532 cd/m2, respectively. The DMAC-TPP[PF6]-based device exhibits efficiency roll-offs of 11.1% (EQE = 13.6%) and 35.3% (EQE = 9.9%) at luminances of 1000 and 5000 cd/m2, respectively. Notably, the 2DMAC-TPP[PF6]-based device reached the maximum EQE at a luminance of 117 cd/m2 and showed low efficiency roll-offs of 7.1% (EQE = 17.0%) and 27.9% (EQE = 13.2%) at practical high luminances of 1000 and 5000 cd/m2, respectively. These device efficiencies and efficiency roll-offs represent the best device performance of ionic-TADF-emitter-based OLEDs hitherto and are comparable with those state-of-the-art partially solution-processed OLEDs based on neutral TADF emitters ( Supporting Information Table S8). The small efficiency roll-offs obtained at high luminances can mainly be attributed to the short-lived TADF emitters, which can alleviate the exciton annihilation in the emitting layers. Conclusion Tetraphenylphosphonium cation has been used as the electron acceptor to construct highly efficient ionic TADF emitters with D–A+ and D–A+–D architectures. These ionic TADF emitters, namely DMAC-TPP[PF6] and 2DMAC-TPP[PF6], show high PLQYs of 0.75 and 0.91 and short decay fluorescence lifetimes of 1.67 and 1.43 μs in doped films, respectively. High EL performance has been achieved in partially solution-processed OLEDs. 2DMAC-TPP[PF6]-based device realized EQEmax of 18.3% and peak luminance of 14532 cd/m2. More importantly, the EQE values remain high with only tiny efficiency roll-off even at practical high luminances. Our results suggest that cationic acceptors are a promising choice for the design of high-performance TADF materials and that this research opens an avenue for designing new ionic TADF materials. Supporting Information Supporting Information is available and detailed and photophysical properties, of rate (see the Data at device fabrication and device performance and of is of to Information This research was as a result of a from the Key Research of the Chinese Academy of the Science of the Science of Fujian the Fujian Science and Technology Innovation Laboratory for Optoelectronic Information of and the Innovation of Xiamen and and the Research of Xiamen of a State and for Organic 2. 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