Tunable Photophysical Properties Research Articles

Multimode Stimuli-Responsive Room-Temperature Phosphorescence Achieved by Doping Butterfly-like Fluorogens into Crystalline Small-Molecular Hosts.

Materials with stimuli-responsive purely organic room-temperature phosphorescence (RTP) exempt from exquisite molecular design and complex preparation are highly desirable but still relatively rare. Moreover, most of them work in a single switching mode. Herein, we employ a versatile host-guest-doped strategy to facilely construct efficient RTP systems with multimode stimuli-responsiveness without ingenious molecular design. By conveniently doping butterfly-like guests, namely, N,N'-diphenyl-dihydrodibenzo[a,c]phenazines (DPACs), featured with vibration-induced emission into the small-molecular hosts via various methods, RTP systems with finely tunable photophysical properties are readily obtained. Through systematic mechanistic studies and with the aid of a series of control experiments, we unveil the critical role of the host crystallinity in achieving efficient RTP. By virtue of the inherent environmental sensitivity of both RTP and fluorescence of the DPACs, our systems exhibit multiple-stimuli-responsiveness with the luminescence not only switching between the fluorescence and phosphorescence but also continuously changing in the fluorescence color. Advanced dynamic anticounterfeiting and multilevel information encryption is thereby realized.

A Chirally Locked Bis-perylene Diimide Macrocycle: Consequences for Chiral Self-Assembly and Circularly Polarized Luminescence.

Macrocycles containing chiral organic dyes are highly valuable for the development of supramolecular circularly polarized luminescent (CPL) materials, where a preorganized chiral framework is conducive to directing π-π self-assembly and delivering a strong and persistent CPL signal. Here, perylene diimides (PDIs) are an excellent choice for the organic dye component because, alongside their tunable photophysical and self-assembly properties, functionalization of the PDI's core yields a twisted, chiral π-system, capable of CPL. However, configurationally stable PDI-based macrocycles are rare, and those that are also capable of π-π self-assembly beyond dimers are unprecedented, both of which are advantageous for robust self-assembled chiroptical materials. In this work, we report the first bay-connected bis-PDI macrocycle that is configurationally stable (ΔG⧧ > 155 kJ mol-1). We use this chirally locked macrocycle to uncover new knowledge of chiral PDI self-assembly and to perform new quantitative CPL imaging of the resulting single-crystal materials. As such, we discover that the chirality of a 1,7-disubstituted PDI provides a rational route to designing H-, J- and concomitant H- and J-type self-assembled materials, important arrangements for optimizing (chir)optical and charge/energy transport properties. Indeed, we reveal that CPL is amplified in the single crystals of our chiral macrocycle by quantifying the degree of emitted light circular polarization from such materials for the first time using CPL-Laser Scanning Confocal Microscopy.

Single Benzene Yellow Fluorophore: Anodic Synthesis of Tetrahydrobenzodifuran

Fluorophores have proven to be indispensable tools in fields ranging from physics, chemistry, and biology. Organic fluorophores have high degrees of freedom in their molecular designs, which is essential for fundamental applications such as imaging probes. The strategies to produce organic fluorophores with improved physicochemical properties are two-fold, including an extension of aryl systems and a construction of push-pull motifs, where electron-donating and -withdrawing groups are conjugated. When used in bio-related research fields, the construction of push-pull motifs is preferred in terms of water solubility and molecular size, since the extension of aryl systems produces relatively large hydrophobic, planar, and thus highly crystalline, structures.The early work by Shimizu in 2009 triggered explosive growth in the development of new single-benzene fluorophores. From the viewpoints of synthetic practicality and unique and tunable photophysical properties, installing diagonally symmetrical substitution patterns with the same electron-donating and -withdrawing groups is the simplest strategy to create new single-benzene fluorophores.During the course of our studies focusing on electrochemical cycloadditions, we found that dihydrobenzofuran derivatives armed with electron-donating and -withdrawing groups exhibited bright fluorescence. In order to suppress molecular motions that cause non-radiative transitions, formation of a furan ring is effective in restricting bond rotation. Furthermore, we found that symmetrically substituted dialkoxy-dicarbonylbenzenes exhibited unique bright fluorescence. In this study, we successfully demonstrate that constructing symmetrical push-pull motifs in combination with restricting bond rotations is the key to creating small yet brightly emitting fluorophores. The anodically constructed tetrahydrobenzodifuran moiety has proven to be an effective core architecture to realize unique and powerful single-benzene fluorophores with high quantum yields and large Stokes shifts.

Multifunctional Nanoplatform for NIR-II Imaging-Guided Synergistic Oncotherapy

Tumors are a major public health issue of concern to humans, seriously threatening the safety of people’s lives and property. With the increasing demand for early and accurate diagnosis and efficient treatment of tumors, noninvasive optical imaging (including fluorescence imaging and photoacoustic imaging) and tumor synergistic therapies (phototherapy synergistic with chemotherapy, phototherapy synergistic with immunotherapy, etc.) have received increasing attention. In particular, light in the near-infrared second region (NIR-II) has triggered great research interest due to its penetration depth, minimal tissue autofluorescence, and reduced tissue absorption and scattering. Nanomaterials with many advantages, such as high brightness, great photostability, tunable photophysical properties, and excellent biosafety offer unlimited possibilities and are being investigated for NIR-II tumor imaging-guided synergistic oncotherapy. In recent years, many researchers have tried various approaches to investigate nanomaterials, including gold nanomaterials, two-dimensional materials, metal sulfide oxides, polymers, carbon nanomaterials, NIR-II dyes, and other nanomaterials for tumor diagnostic and therapeutic integrated nanoplatform construction. In this paper, the application of multifunctional nanomaterials in tumor NIR-II imaging and collaborative therapy in the past three years is briefly reviewed, and the current research status is summarized and prospected, with a view to contributing to future tumor therapy.

Photocatalytic synthesis of fluorescent and polarity-sensitive β-thiolated diketones for LDs-specific imaging

Fluorophores with easily tunable photophysical properties are highly desirable for bio-imaging. Herein, we develop a photocatalytic method for direct thiolation of β-diketone compounds with Rose Bengal as the photocatalyst under white light irradiation. The β-thiolated diketone compounds show a polarity-sensitive fluorescence emission and can be used for lipid droplets (LDs)-specific imaging with a high signal-to-noise ratio. We believe this photocatalytic method for direct preparation of fluorescent and polarity-sensitive β-thiolated diketones is promising for bioimaging applications.

Chiral induction and Sb3+ doping in indium halides to trigger second harmonic generation and circularly polarized luminescence

Recently, organic-inorganic hybrid metal halides (HMHs) have attracted extensive attention as promising multifunctional materials by virtue of their structural diversity and tunable photophysical properties. However, it remains a challenge to design HMHs with specific functions on demand. Herein, by introducing R/S-methylbenzylamine (R/S-MBA) and doping Sb3+, we have achieved both second harmonic generation (SHG) and circularly polarized luminescence (CPL) properties in lead-free indium halides. The introduction of chiral organic cations can break the symmetry and induce the indium halides to crystallize in the chiral space group. The Sb3+ with ns2 electronic configuration can serve as the dopants to promote the formation of self-trapped excitons, so as to activate highly efficient luminescence. As a result, the as-prepared Sb3+ doped (R/S-MBA)3InCl6 show not only SHG responses but also CPL signals with luminescence dissymmetry factor of −5.3 × 10−3 and 4.7 × 10−3. This work provides a new inspiration for the exploitation of chiral multifunctional materials.

Functional organogold(III) complexes with bidentate cyclometalating ligands

The advancement of organometallic chemistry over the past decades has accelerated the development of functional materials based on metal complexes. In particular, organometallic complexes based on the gold(III) system have been attracting increasing attention. The square planar gold(III) metal center can coordinate to different chromophoric ligands as in related iridium(III) and platinum(II) systems, allowing the synthesis of another library of metal-based functional materials. Bidentate cyclometalating ligands such as 2-phenylpyridine derivatives are amongst the most commonly used class of ligands for the synthesis of transition metal complexes and they have been used for the preparation of gold(III) complexes with tunable photophysical properties. In this review, the recent progress in the development of organometallic gold(III) complexes based on these bidentate cyclometalating ligands will be discussed, with specific foci on the applications of these gold(III) complexes as emitters for organic light-emitting diodes as well as their biological applications.

Catalyst-Free Four-Component Spiropolymerization for the Construction of Spirocopolymers with Tunable Photophysical Properties

Catalyst-Free Four-Component Spiropolymerization for the Construction of Spirocopolymers with Tunable Photophysical Properties

Living Suzuki-Miyaura Catalyst-Transfer Polymerization for Precision Synthesis of Length-Controlled Armchair Graphene Nanoribbons and Their Block Copolymers.

The bottom-up synthesis of graphene nanoribbons (GNRs) offers a promising approach for designing atomically precise GNRs with tuneable photophysical properties, but controlling their length remains a challenge. Herein, we report an efficient synthetic protocol for producing length-controlled armchair GNRs (AGNRs) through living Suzuki-Miyaura catalyst-transfer polymerization (SCTP) using RuPhos-Pd catalyst and mild graphitization methods. Initially, SCTP of a dialkynylphenylene monomer was optimized by modifying boronates and halide moieties on the monomers, affording poly(2,5-dialkynyl-p-phenylene) (PDAPP) with controlled molecular weight (Mn up to 29.8k) and narrow dispersity (Đ = 1.14-1.39) in excellent yield (>85%). Subsequently, we successfully obtained N = 5 AGNRs by employing a mild alkyne benzannulation reaction on the PDAPP precursor and confirmed their length retention by size-exclusion chromatography. In addition, photophysical characterization revealed that a molar absorptivity was directly proportional to the length of the AGNR, while its highest occupied molecular orbital (HOMO) energy level remained constant within the given AGNR length. Furthermore, we prepared, for the very first time, N = 5 AGNR block copolymers with widely used donor or acceptor-conjugated polymers by taking advantage of the living SCTP. Finally, we achieved the lateral extension of AGNRs from N = 5 to 11 by oxidative cyclodehydrogenation in solution and confirmed their chemical structure and low band gap by various spectroscopic analyses.

Sn-Induced Synthesis of Highly Crystalline and Size-Confined Si Nanorods at Moderately High Temperatures Using Hydrogen Silsesquioxane

Size-confined Si nanorods (NRs) have gained notable interest because of their tunable photophysical properties that make them attractive for optoelectronic, charge storage, and sensor technologies. However, established routes for fabrication of Si NRs use well-defined substrates and/or nanoscopic seeds as promoters that cannot be easily removed, hindering the investigation of their true potential and physical properties. Herein, we report a facile, one-step route for the fabrication of Si NRs via thermal disproportionation of hydrogen silsesquioxane (HSQ) in the presence of a molecular tin precursor (SnCl4) at a substantially lower temperature (450 °C) compared to those used in the synthesis of size-confined Si nanocrystals (>1000 °C). The use of these precursors allows the facile isolation of phase-pure Si NRs via HF etching and subsequent surface passivation with 1-dodecene via hydrosilylation. The diameters (7.7–16.5 nm) of the NRs can be controlled by varying the amount of SnCl4 (0.2–3.0%) introduced during the HSQ synthesis. Physical characterization of the NRs suggests that the diamond cubic structure is not affected by SnCl4, HF etching, and hydrosilylation. Surface analysis of NRs indicates the presence of Si0 and Sin+ species, which can be attributed to core Si and surface Si species bonded to dodecane ligands, respectively, and a systematic variation of the Si0:Si–C ratio with the NR diameter. The NRs show strong size confinement effects with solid-state absorption onsets (2.51–2.80 eV) and solution-state (Tauc) indirect energy gaps (2.54–2.70 eV) that can be tuned by varying the diameter (16.5–7.7 nm). Photoluminescence (PL) and time-resolved PL (TRPL) studies reveal size-dependent emission (1.95–2.20 eV) with short, nanosecond lifetimes across the visible spectrum, which trend closely with absorption trends seen in solid-state absorption data. The facile synthesis developed for size-confined Si NRs with high crystallinity and tunable optical properties will promote their application in optoelectronic, charge storage, and sensing studies.

Exploring the reactivity of formylporphyrins with 3-(diethylamino)phenol. Synthesis, spectroscopic properties and singlet oxygen generation of a new porphyrin–rosamine conjugate

The design of novel molecular structures with tunable photophysical properties is an important research field for many applications including optoelectronics, sensing and bioimaging. Porphyrin and rhodamine/rosamine derivatives are among the most studied and relevant chemosensors and imaging probes due to their attractive photophysical properties, such as high absorption coefficients and long emission wavelengths. In this work, we present the synthesis and the structural characterization of a new porphyrin–rosamine conjugate H2P3 and its related triarylmethane precursors H2P1 and H2P2. The photophysical properties of H2P1, H2P2 and H2P3, and their ability to chelate iron(III) and copper(II) ions, were evaluated by absorption and emission spectroscopy. The formation of copper(II) complexes was confirmed by electron paramagnetic resonance (EPR), which also allowed the detection of an intense and stable radical signal for the free-base H2P3. Further studies involving the addition of the 2,2,6,6-tetramethylpiperidine spin trap to derivatives H2P1, H2P2 and H2P3, showed that only H2P3 gives rise to an EPR detectable signal due to a strong generation of singlet oxygen.

Piezochromism in Dynamic Three-Dimensional Covalent Organic Frameworks.

Piezochromic materials with pressure-dependent photoluminescence tuning properties are important in many fields, such as mechanical sensors, security papers, and storage devices. Covalent organic frameworks (COFs), as an emerging class of crystalline porous materials (CPMs) with structural dynamics and tunable photophysical properties, are suitable for designing piezochromic materials, but there are few related studies. Herein, we report two dynamic three-dimensional COFs based on aggregation-induced emission (AIE) or aggregation-caused quenching (ACQ) chromophores, termed JUC-635 and JUC-636 (JUC = Jilin University China), and for the first time, study their piezochromic behavior by diamond anvil cell technique. Due to the various luminescent groups, JUC-635 has completely different solvatochromism and molecular aggregation behavior in the solvents. More importantly, JUC-635 with AIE effect exhibits a sustained fluorescence upon pressure increase (~3 GPa), and reversible sensitivity with high-contrast emission differences (Δλem = 187 nm) up to 12 GPa, superior to other CPMs reported so far. Therefore, this study will open a new gate to expand the potential applications of COFs as exceptional piezochromic materials in pressure sensing, barcoding, and signal switching.

Piezochromism in Dynamic Three‐Dimensional Covalent Organic Frameworks

AbstractPiezochromic materials with pressure‐dependent photoluminescence tuning properties are important in many fields, such as mechanical sensors, security papers, and storage devices. Covalent organic frameworks (COFs), as an emerging class of crystalline porous materials (CPMs) with structural dynamics and tunable photophysical properties, are suitable for designing piezochromic materials, but there are few related studies. Herein, we report two dynamic three‐dimensional COFs based on aggregation‐induced emission (AIE) or aggregation‐caused quenching (ACQ) chromophores, termed JUC‐635 and JUC‐636 (JUC=Jilin University China), and for the first time, study their piezochromic behavior by diamond anvil cell technique. Due to the various luminescent groups, JUC‐635 has completely different solvatochromism and molecular aggregation behavior in the solvents. More importantly, JUC‐635 with AIE effect exhibits a sustained fluorescence upon pressure increase (≈3 GPa), and reversible sensitivity with high‐contrast emission differences (Δλem=187 nm) up to 12 GPa, superior to other CPMs reported so far. Therefore, this study will open a new gate to expand the potential applications of COFs as exceptional piezochromic materials in pressure sensing, barcoding, and signal switching.

Recent Advances of Diketopyrrolopyrrole Derivatives in Cancer Therapy and Imaging Applications.

Cancer is threatening the survival of human beings all over the world. Phototherapy (including photothermal therapy (PTT) and photodynamic therapy (PDT)) and bioimaging are important tools for imaging-mediated cancer theranostics. Diketopyrrolopyrrole (DPP) dyes have received more attention due to their high thermal and photochemical stability, efficient reactive oxygen species (ROS) generation and thermal effects, easy functionalization, and tunable photophysical properties. In this review, we outline the latest achievements of DPP derivatives in cancer therapy and imaging over the past three years. DPP-based conjugated polymers and small molecules for detection, bioimaging, PTT, photoacoustic imaging (PAI)-guided PTT, and PDT/PTT combination therapy are summarized. Their design principles and chemical structures are highlighted. The outlook, challenges, and future opportunities for the development of DPP derivatives are also presented, which will give a future perspective for cancer treatment.

Fabrication of a Large-Area Flexible Scintillating Membrane for High-Resolution X-ray Imaging Using an AIEgen-Functionalized Metal-Organic Framework.

With the growing demand for X-ray imaging, especially for three-dimensional objects with curved surfaces, a large-area flexible X-ray imaging membrane based on scintillating materials becomes the focus of vigorous investigation. Among the developed scintillators, metal-organic frameworks (MOFs) featuring tunable photophysical properties and marked luminescence stability hold great promise for serving as ideal X-ray scintillators. Here, we report a flexible composite scintillating membrane with superior imaging performance. The membrane is achieved by embedding an aggregation-induced emission (AIE) luminogen (AIEgen, H4ETTC)-functionalized MOF scintillator (Y-PCN-94) into a polymer matrix (PDMS). Notably, Y-PCN-94 exhibits a strong AIE effect under both ultraviolet (UV) light and X-ray irradiation, which is also the first time that the AIE effect was observed in the MOF system under an ionizing radiation field. This also gives the material promising radioluminescence properties, such as a low X-ray detection limit (1.6 μGy s-1) and high imaging resolution (>14.3 lp mm-1), which can be mainly attributed to the combination of the AIE effect and strong X-ray stopping power. This work demonstrates that incorporating AIEgens into MOFs or other frameworks can offer an alternative approach for producing high-performance X-ray scintillators.

Acidochromism of amino-substituted indolizine chromophores: Towards white light emission

There is a continuous interest in the development of advanced materials with tunable photophysical properties, among which white light emission represents a major challenge. Indolizines are a kind of azaheterocycles that have gained a great deal of attention in the recent past due to their intriguing photophysical behavior. We report herein on the synthesis of new push–pull indolizines bearing amino and electron-withdrawing groups at positions 1 and 7, respectively, and on their optical response in acidic medium. Exclusive protonation on the amino group has led to a hypsochromic shift in the emission spectra. Interestingly, white photoluminescence can be attained by adjusting the amount of acid as a result of color complementarity between neutral and charged species. Moreover, Density Functional Theory (DFT) calculations on the molecular structure and photophysical properties of these compounds are in agreement with the experimental results, providing very useful information about the main electronic transitions and the influence of protonation on the optical transitions.

Isolation, Reactivity, and Tunable Properties of a Strained Antiaromatic Osmacycle.

Strain and antiaromaticity in compounds are recognized as two substantial destabilizing features, and consequently, realization of dual destabilizing features in a single molecule is challenging and far more difficult in a single ring. Moreover, transformation of an antiaromatic framework to different antiaromatic or aromatic species is a significant subject in antiaromatic chemistry and has attracted increasing interest. In this work, we isolated a highly strained antiaromatic metallacycle in which a cyclic metal vinylidene unit is embedded. Computational studies revealed its ring strain energies and antiaromatic character and showed that the metal incorporation and the phosphonium substituents play a crucial role in its stabilization. The mechanism of its formation has been illustrated by density functional theory (DFT) calculations and the isolation of a key intermediate. We further discovered diverse reactivities and structural reshuffling of this unusual strained antiaromatic complex according to its two destabilizing characters. We obtained two isomers of metallaindenes fused with oxiranes from the direct oxidation of the metal vinylidene or by nucleophilic addition to an isolated metallacyclocumulene formed by the reaction of metal vinylidene with hydroxide ion, achieving a reconfiguration of the antiaromatic framework. Transformations of the antiaromatic metallacycle by electrophiles to various aromatic metallaindynes have been achieved, and that a condensed Fukui function was employed to confirm the regioselectivity of the electrophilic additions, and the acid/base-induced aromaticity switch along with tunable photophysical properties were investigated. These interesting transformations not only enrich the chemistry of metal vinylidenes and antiaromatics and could also perform potentially as switchable optical materials.

1,2,5,6‐Naphthalene Diimides: A Class of Promising Building Blocks for Organic Semiconductors†

Comprehensive SummaryOrganic semiconductors have drawn extensive attention due to their optoelectronic properties and wide applications in organic optoelectronics. In comparison with the popular 1,4,5,8‐naphthalene diimides (1,4,5,8‐NDIs), the angular‐shaped 1,2,5,6‐NDIs have exhibited tunable photophysical properties, self‐assembly behaviors and charge transporting properties. Due to these unique features, 1,2,5,6‐NDIs show great potential for construction of high performance π‐functional materials. In this review, we highlight the recent advances and future prospects of 1,2,5,6‐NDI‐based π‐systems in the field of organic optoelectronics, including molecular design, synthesis, structure‐property relationships as well as the applications in high performance organic field‐effect transistors, organic photovoltaics, perovskite solar cells, and so on. What is the most favorite and original chemistry developed in your research group?Chemistry of π‐functional materials by using naphthalene and azulene as the basic structural units.How do you get into this specific field? Could you please share some experiences with our readers?This comes from my previous research experience, independent thinking and academic exchange & discussion. When I was a PhD student, my research topic focused on p‐type organic semiconductors. Since I independently carried out scientific research, my research interest turned to developing more challenging n‐type organic semiconductors by using core‐expanded 1,4,5,8‐naphthalene diimides (NDIs). Later on, 1,2,5,6‐NDIs as high‐performance organic semiconductors, the topic of this review paper, entered our study perspective based on the concept of isomerism. Also, based on the concept of isomerism and academic discussion, azulene, the isomer of naphthalene with unique chemical structure and physicochemical properties, became the dominant building block for constructing novel π‐functional materials in my group.How do you supervise your students?Select a research topic with scientific significance and certain challenges, let students consult and intensively read relevant literatures and obtain research inspiration, basic knowledge, experimental skills, writing skills, etc. Encourage students to think independently, try more, and pay more attention to communication and cooperation. Fully train students to write research papers independently. The last but not the least, advocate the academic spirit of being innovative, pursuing excellence as well as rigorous scholarship.What is the most important personality for scientific research?Curiosity and perseverance.What are your hobbies?Reading and walking.If you have anything else to tell our readers, please feel free to do so.No one can imprison your mind and hold your hand to prevent you from doing research work, follow your heart to do what you like and different from others.

Energy-Trapping Management in X-Ray Storage Phosphors for Flexible 3D Imaging.

X-ray imaging has received sustained attention for healthcare diagnostics and nondestructive inspection. To develop photonic materials with tunable photophysical properties in principle accelerates radiation detection technologies. Here the rational design and synthesis of doped halide perovskite CsCdCl3 :Mn2+ , R4+ (R = Ti, Zr, Hf, and Sn) are reported as next generation X-ray storage phosphors, and the capability is greatly improved by trap management via Mn2+ site occupation manipulation and heterovalent substitution. Specially, CsCdCl3 :Mn2+ , Zr4+ displays zero-thermal-quenching (TQ) radioluminescence and anti-TQ X-ray-activated persistent luminescence even up to 448 K, further revealing the charge-carrier compensation and redeployment mechanisms. X-ray imaging with the resolution of 12.5 lp mm-1 is demonstrated, and convenient 3D X-ray imaging for the curved objects is realized in a time-lapse manner. This work demonstrates efficient modulation of energy traps to achieve high storage capacities and promote future research into flexible X-ray detectors.

Broadband Flexible CuPc–PCBM Photodetector With Responsivity in Different Spectral Regions

Organic photodetectors have gained immense attention in the field of organic electronics because of their diverse applications, like image sensing, optical communication, health monitoring, and so on. These types of devices possess tunable photophysical and optoelectronic properties. Considering the mechanical flexibility, lightweight, and high performance of polyethylene terephthalate (PET) as substrate, a flexible organic photodetector (OPD) with diode architecture involving Copper phthalocyanine (CuPc) as the donor and Phenyl-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">60</sub> -butyric acid methyl ester (PC <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">60</sub> BM) as the acceptor has been fabricated. The maximum EQE of 10.2% was perceived. The OPD exhibited a decent spectral response in the full visible range with the highest value at ~385nm. Characteristics of this flexible OPD with an active organic layer and conducting polymer-based hole transport layer have been explored thoroughly under the different spectral ranges of the solar spectrum.