Molecular Design Strategy Research Articles

Electron-Deficient Organic Molecules Based on B←N Unit: A N-Type Room-Temperature Chemiresistive Sensors with Moisture Resistance.

Organic molecules with tailorable chemical structures, high stability, and solution processability have great potential in the sensing field. Compared with p-type organic small molecules (OSMs), the electron-dominated n-type analogs show superior conductivity when exposed to reducing gases, which can achieve outstanding sensor signal-to-noise ratios. However, inadequate humidity resistance at room temperature hinders the development of such molecules. Herein, an A-D-π-D-A molecular design strategy is proposed based on electron-deficient B←N units, which results in effective intramolecular charge transport and sensitive responses by extending the π-conjugation bridge. As a result, the ST-2BP with A-D-π-D-A configuration shows a prominent sensitivity of 787 (Ra/Rg) in 20ppm NH3 at room temperature and an almost initial and stable response under different relative humidity conditions, which is the highest among currently reported OSM sensors. Supported by theoretical calculations and in situ FTIR spectra, it is revealed that B←N units, which function as the active centers mediate the specific ammonia adsorption. This study provides a new understanding of the design of high-performance room temperature gas sensing materials by decorating B←N units.

Rational Design of Biocompatible Ir(III) Photosensitizer to Overcome Drug-Resistant Cancer via Oxidative Autophagy Inhibition.

Autophagy is a crucial quality control mechanism that degrades damaged cellular components through lysosomal fusion with autophagosomes. However, elevated autophagy levels can promote drug resistance in cancer cells, enhancing their survival. Downregulation of autophagy through oxidative stress is a clinically promising strategy to counteract drug resistance, yet precise control of oxidative stress in autophagic proteins remains challenging. Here, a molecular design strategy of biocompatible neutral Ir(III) photosensitizers is demonstrated, B2 and B4, for precise reactive oxygen species (ROS) control at lysosomes to inhibit autophagy. The underlying molecular mechanisms for the biocompatibility and lysosome selectivity of Ir(III) complexes are explored by comparing B2 with the cationic or the non-lysosome-targeting analogs. Also, the biological mechanisms for autophagy inhibition via lysosomal oxidation are explored. Proteome analyses reveal significant oxidation of proteins essential for autophagy, including lysosomal and fusion-mediator proteins. These findings are verified in vitro, using mass spectrometry, live cell imaging, and a model SNARE complex. The anti-tumor efficacy of the precise lysosomal oxidation strategy is further validated in vivo with B4, engineered for red light absorbance. This study is expected to inspire thetherapeutic use of spatiotemporal ROS control for sophisticated modulation of autophagy.

Photoresponsive tetracoordinate arylboron smart molecules: Strategies for molecular design and photoresponse mechanisms

AbstractPhotoresponsive smart materials, which exhibit swift or instantaneous responses to external light stimuli, are pivotal for advancing the development of novel smart devices. Among these materials, photoresponsive tetracoordinate arylboron compounds emerge as prominent molecular systems, owing to their captivating photochemical mechanisms and photophysical transformations. In recent years, these molecules have experienced notable progress, leading to the emergence of numerous organic boron photoresponsive molecular systems with innovative structures and exceptional performance. In this comprehensive review, we present a thorough examination of the latest advancements in the field, systematically elucidating the design strategies and structure‐activity relationships of these molecules. Furthermore, we delve into the photoresponse mechanisms of various molecules and summarize their unique characteristics. Ultimately, we analyze the challenges, opportunities, and prospects encountered in this exciting field of research.

Completely Fused Non‐Fullerene Acceptor Enables Efficient Postprocessing‐Free Organic Photovoltaics Cells

AbstractThe photovoltaic performance of organic photovoltaic (OPV) cells can be significantly improved by regulating the aggregation structure and film formation kinetics of the constituent materials. However, many regulation strategies, including the use of additives and annealing, require complex fabrication processes and additional investments, which poses challenges for the industrialization of OPV cells. In this work, a completely fused non‐fullerene acceptor, GS‐20 is designed and synthesized, with strong aggregation properties. The incorporation of GS‐20 as a third component into the PBQx‐TF:eC9‐2Cl‐based cell accelerates aggregation of eC9‐2Cl and improves molecular stacking by promoting film deposition. The as‐cast ternary OPV cells fabricated without any post‐treatments exhibited a high VOC of 0.890 V and a maximum PCE of 19.0%. Moreover, a postprocessing‐free OPV module is fabricated using the blade coating method and obtains a satisfactory PCE of 13.5%, indicating excellent feasibility for large‐scale preparation. This work realizes an efficient postprocessing‐free OPV cell through molecular design and ternary strategy, facilitating the industrialization of OPV technology.

Synergistic π-Extension and Peripheral-Locking of B/N-Based Multi-Resonance Framework Enables High-Performance Pure-Green Organic Light-Emitting Diodes.

Multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters offer natural advantages for creating power-efficient, wide-color-gamut OLEDs. However, current green MR-TADF emitters face challenges in simultaneously achieving high color purity and efficient reverse inter-system crossing (RISC), leading to suboptimal device performance. In this study, we propose a synergistic molecular design approach that combines π-extension and peripheral locking to address these challenges. This approach allows for the construction of quadruple borylated MR-TADF emitters that not only deliver precisely tuned pure-green emission with a narrow full width at half maximum (FWHM) of 15 nm, but also exhibit close-to-unity quantum yield, rapid RISC, and optimal horizontal dipole orientation. The resulting sensitizer-free OLED approaches the BT.2020 standard with CIE coordinates of (0.18, 0.74) and demonstrates impressive external quantum efficiency (EQE) of 36.6% at maximum and 31.8% at 1000 cd m-2. Additionally, the device shows good operational stability, with a lifetime (LT80) of 485 hours at an initial luminance of 1000 cd m-2. This study hence offers a promising molecular design strategy that effectively enhances the comprehensive OLED performance.

Synergistic π‐Extension and Peripheral‐Locking of B/N‐Based Multi‐Resonance Framework Enables High‐Performance Pure‐Green Organic Light‐Emitting Diodes

Multi‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters offer natural advantages for creating power‐efficient, wide‐color‐gamut OLEDs. However, current green MR‐TADF emitters face challenges in simultaneously achieving high color purity and efficient reverse inter‐system crossing (RISC), leading to suboptimal device performance. In this study, we propose a synergistic molecular design approach that combines π‐extension and peripheral locking to address these challenges. This approach allows for the construction of quadruple borylated MR‐TADF emitters that not only deliver precisely tuned pure‐green emission with a narrow full width at half maximum (FWHM) of 15 nm, but also exhibit close‐to‐unity quantum yield, rapid RISC, and optimal horizontal dipole orientation. The resulting sensitizer‐free OLED approaches the BT.2020 standard with CIE coordinates of (0.18, 0.74) and demonstrates impressive external quantum efficiency (EQE) of 36.6% at maximum and 31.8% at 1000 cd m‐2. Additionally, the device shows good operational stability, with a lifetime (LT80) of 485 hours at an initial luminance of 1000 cd m‐2. This study hence offers a promising molecular design strategy that effectively enhances the comprehensive OLED performance.

Layered hybrid superlattices as designable quantum solids.

Crystalline solids typically show robust long-range structural ordering, vital for their remarkable electronic properties and use in functional electronics, albeit with limited customization space. By contrast, synthetic molecular systems provide highly tunable structural topologies and versatile functionalities but are often too delicate for scalable electronic integration. Combining these two systems could harness the strengths of both, yet realizing this integration is challenging owing to distinct chemical bonding structures and processing conditions. Two-dimensional atomic crystals comprise crystalline atomic layers separated by non-bonding van der Waals gaps, allowing diverse atomic or molecular intercalants to be inserted without disrupting existing covalent bonds. This enables the creation of a diverse set of layered hybrid superlattices (LHSLs) composed of alternating crystalline atomic layers of variable electronic properties and self-assembled atomic or molecular interlayers featuring customizable chemical compositions and structural motifs. Here we outline strategies to prepare LHSLs and discuss emergent properties. With the versatile molecular design strategies and modular assembly processes, LHSLs offer vast flexibility for weaving distinct chemical constituents and quantum properties into monolithic artificial solids with a designable three-dimensional potential landscape. This opens unprecedented opportunities to tailor charge correlations, quantum properties and topological phases, thereby defining a rich material platform for advancing quantum information science.

Visualizing Triplet Energy Transfer in Organic Near-Infrared Phosphorescent Host-Guest Materials.

Limited by the energy gap law, purely organic materials with efficient near-infrared room temperature phosphorescence are rare and difficult to achieve. Additionally, the exciton transition process among different emitting species in host-guest phosphorescent materials remains elusive, presenting a significant academic challenge. Herein, using a modular nonbonding orbital-π bridge-nonbonding orbital (n-π-n) molecular design strategy, we develop a series of heavy atom-free phosphors. Systematic modification of the π-conjugated cores enables the construction of a library with tunable near-infrared phosphorescence from 655 to 710 nm. These phosphors exhibit excellent performance under ambient conditions when dispersed into a 4-bromobenzophenone host matrix, achieving an extended lifetime of 11.25 ms and a maximum phosphorescence efficiency of 4.2 %. Notably, by eliminating the interference from host phosphorescence, the exciton transition process in hybrid materials can be visualized under various excitation conditions. Spectroscopic analysis reveals that the improved phosphorescent performance of the guest originates from the triplet-triplet energy transfer of abundant triplet excitons generated independently by the host, rather than from enhanced intersystem crossing efficiency between the guest singlet state and the host triplet state. The findings provide in-depth insights into constructing novel near-infrared phosphors and exploring emission mechanisms of host-guest materials.

Visualizing Triplet Energy Transfer in Organic Near‐Infrared Phosphorescent Host‐Guest Materials

AbstractLimited by the energy gap law, purely organic materials with efficient near‐infrared room temperature phosphorescence are rare and difficult to achieve. Additionally, the exciton transition process among different emitting species in host–guest phosphorescent materials remains elusive, presenting a significant academic challenge. Herein, using a modular nonbonding orbital‐π bridge‐nonbonding orbital (n‐π‐n) molecular design strategy, we develop a series of heavy atom‐free phosphors. Systematic modification of the π‐conjugated cores enables the construction of a library with tunable near‐infrared phosphorescence from 655 to 710 nm. These phosphors exhibit excellent performance under ambient conditions when dispersed into a 4‐bromobenzophenone host matrix, achieving an extended lifetime of 11.25 ms and a maximum phosphorescence efficiency of 4.2 %. Notably, by eliminating the interference from host phosphorescence, the exciton transition process in hybrid materials can be visualized under various excitation conditions. Spectroscopic analysis reveals that the improved phosphorescent performance of the guest originates from the triplet‐triplet energy transfer of abundant triplet excitons generated independently by the host, rather than from enhanced intersystem crossing efficiency between the guest singlet state and the host triplet state. The findings provide in‐depth insights into constructing novel near‐infrared phosphors and exploring emission mechanisms of host–guest materials.

Recent progress in high-performance thermally activated delayed fluorescence exciplexes based on multiple reverse intersystem crossing channels

In the field of organic light-emitting diodes (OLEDs), exciplex materials with thermally activated delayed fluorescence (TADF) characteristics have garnered significant attention in recent years owing to their potential for high fluorescence efficiency, primarily achieved through the reverse intersystem crossing (RISC) process. By converting non-radiative triplet states to radiative singlet states, the RISC process can effectively regulate exciton behavior, resulting in the harvest of triplet excitons and the improvement of luminescence efficiency. Recently, multi-RISC strategies have been developed to further enhance the performance of TADF exciplex materials and devices. In this paper, we review these research progress in this area. We classify molecular design strategies according to the composition of exciplexes, discuss the design principles and energy-harvesting mechanism of high-performance TADF exciplexes based on multi-RISC strategies, and prospect their further research and development. The progressive endeavors summarized in this review may inspire further research on material design and device fabrication, and promote the development of OLED applications.

Spiro‐Based Thermally Activated Delayed Fluorescence Emitters for Organic Light‐Emitting Diodes

AbstractSpiro structures, possessing unique π‐electron systems, large steric hindrance, high glass transition temperature, and chemical stability, serve as critical structural building blocks in constructing thermally activated delayed fluorescence (TADF) emitters. The incorporation of various heteroatoms such as oxygen, sulfur, and nitrogen in 9,9′‐spirobifluorene generates diverse spiro structures like spiro[fluorene‐9,9′‐xanthene], spiro[fluorene‐9,9′‐thioxanthene], and spiro[acridine‐9,9′‐fluorene]. Based on the charge transfer characteristics, TADF emitters built upon spiro structures can be classified into various types, including twisted intramolecular charge transfer, through‐space charge transfer, multiresonance, and exciplex‐type TADF emitters. This review systematically highlights the recent progress in the research on TADF emitters comprised of spiro‐structured aromatics. It intricately explores the molecular design strategies, material synthesis methods, understanding of photophysical attributes, and analysis of organic light‐emitting diode performance. Concurrently, it sketches out the challenges faced in the commercial application stage while providing an outlook for potential research trajectories.

Conformational flexibility of a novel Cu(I)-based adsorbent enhancing the selectivity of adsorptive desulfurization

Adsorptive desulfurization (ADS) is a promising technique for producing clean fuels with ultra-low sulfur, and various metal-functionalized adsorbents for desulfurization have been successively investigated. Unfortunately, ADS usually suffers from the low adsorptive selectivity in the presence of organic competitors. Herein, we report the triangular copper(I) 4-nitro-3,5-di(trifluoromethyl)pyrazolate (Cu3pz3) as a novel adsorbent to achieve a high selectivity via short Cu(I) – sulfur bond, the S-content (as DBT) can be reduced from 100 mg S/L to ∼ 9 mg S/L in the toluene-iso-octane model oil (v:v = 15:85) after a static adsorption at 298 K under the adsorbent dose of 3.65 g/L, which is much better than the adsorption performance exhibited by a structurally similar adsorbent – Ag3pz3 (reduced from 100 mg S/L to ∼ 56 mg S/L at the same condition). Furthermore, the adsorption mechanism has been investigated at the molecular level, unveiling a correlation between the ADS selectivity and the strength of Cu(I) – S bonding. Finally, some molecular design strategies have been proposed for further improvement of the performance of ADS adsorbent.

Covalently Merging Ionic Liquids and Conjugated Polymers: A Molecular Design Strategy for Green Solvent‐Processable Mixed Ion–Electron Conductors Toward High‐Performing Chemical Sensors (Adv. Funct. Mater. 45/2024)

Covalently Merging Ionic Liquids and Conjugated Polymers: A Molecular Design Strategy for Green Solvent‐Processable Mixed Ion–Electron Conductors Toward High‐Performing Chemical Sensors (Adv. Funct. Mater. 45/2024)

Introducing electron-rich thiophene bridges in hot exciton emitter for efficient non-Doped near-infrared OLEDs with low turn-on voltages

The development of near-infrared (NIR) luminescent materials featuring high photoluminescence quantum yield (ΦPL) at aggregated state is of great significance for achieving highly efficient non-doped organic light-emitting diodes (OLEDs) but remains formidable challenging. Herein, a design strategy of introducing electron-rich thiophene groups between electron acceptor and donor is proposed for efficient NIR luminescent materials, and a tailored D-π-A-π-D type emitter, namely, 4,4′-(benzo[c][1,2,5]thiadiazole-4,7-diylbis(thiophene-5,2-diyl))bis(N,N-diphenylaniline) (TPATBT), is designed and prepared. The photophysical investigation and density functional theory analysis disclose that TPATBT is a hot exciton emitter feature with hybridized local and charge-transfer state. Additionally, TPATBT demonstrates aggregation-induced emission characteristic, prefers high thermal stability, and exhibits a strong emission at 692 nm with a decent ΦPL of 20 % in the neat film. The non-doped device based on TPATBT neat film presents a maximum external quantum efficiency (ηext,max) of 1.22 % with electroluminescence peak at 718n m. Moreover, we first try to use interlayer sensitization to sensitize non-doped devices, which achieves better ηext,max of 1.34 % with low turn-on voltage of 3.2 V. The proposed molecular design strategy in this work is promising for exploring robust NIR luminescent materials for high-performance OLEDs.

Strategic Design of Anion-Responsive Triarylboranes Exhibiting Colorimetric and Fluorometric Red-Shift for Sensing and Optoelectronic Applications.

Triarylboranes (TABs) have been employed as colorimetric and/or fluorometric anion sensors. The majority of TAB-based anion sensors exhibit blue-shift modes of absorption and photoluminescence (PL) or turn off of PL, attributed to the intrinsic electronic polarity of the trivalent boron unit in their molecular designs. In this Concept article, we introduce a novel approach to modulating the photophysical properties of TABs toward a red-shift mode by balancing the dual, opposing roles of the amine-bridged TAB (phenazaborine). This molecular design strategy enables significant changes in color and emission response to anions, shifting to the lower energy regime in solution. Additionally, this approach is applicable to the solid-state modulation of PL in films and organic light-emitting diodes (OLEDs).

Non‐Fluorinated Cyclic Ether‐Based Electrolyte with Quasi‐Conjugate Effect for High‐Performance Lithium Metal Batteries

AbstractFluorinated ether‐based electrolytes are commonly employed in lithium metal batteries (LMBs) to attenuate the coordination ability of ether solvents with Li+ and induce inorganic‐rich interphase, whereas fluorination inevitably introduces exorbitant production expenses and environmental anxieties. Herein, a non‐fluorinated molecular design strategy has been conceptualized by incorporating methoxy as an electron‐donating group to generate a quasi‐conjugate effect for tuning the affinity of Li+‐solvent, thereby enabling the cyclic ether solvent 2‐methoxy‐1,3‐dioxolane with weak solvation ability and exceptional Li metal‐compatibility. Accordingly, the optimized electrolyte exhibits anion‐dominant solvation structure for inorganic‐rich interphase and fulfills an impressive Li plating/stripping Coulombic efficiency of 99.6 %. As‐fabricated Li||LiFePO4 full cells with limited Li (N/P=2.5) showcase a high capacity retention of 83 % after 150 cycles, indicating excellent cycling stability. Moreover, the full LMBs demonstrate exceptional tolerance towards a wide temperature range from −20 °C to 60 °C, displaying a remarkable capacity retention of 90 % after 110 cycles at −20 °C. Such a molecular design strategy offers a promising avenue for electrolyte engineering beyond fluorination in order to cultivate high‐performance LMBs.

Theoretical exploration of energetic molecular design strategy: functionalization of C or N and structural selection of imidazole or pyrazole.

In researching energetic materials with high energy density, it is an effective method to introduce explosophoric groups. In this study, four series of energetic compounds were designed by functionalizing with C- or N-, introducing energetic groups -CH(NO2)2, -CF(NO2)2, -C(NO2)2(NF2), -C(NO2)3, and-CH(NF2)2 into imidazole and pyrazole structures. Density functional theory was employed to optimize the structure of the target compound and subsequently to predict and evaluate its performance based on this. Meanwhile, the sensitivity of the compounds was predicted based on their electrostatic potential analysis. Following analysis of the geometric structure, detonation performance, and sensitivity of the compounds, three factors were discussed: energetic groups, functionalization methods, and skeleton structure differences. The results indicate that C-functionalization has advantages only in density, but N-functionalization is better in thermal stability, heat of formation, and sensitivity. Meanwhile, the data shows that imidazole-based compounds exhibited greater density and detonation performance in the target compounds designed within this study, while pyrazoles have a higher heat of formation and chemical stability. By analyzing the design strategy of C- or N-functionalization of novel high-energy groups on energetic imidazole or pyrazole rings and selecting a more suitable molecular construction strategy, this study provides a theoretical approach for the development of new energetic materials with excellent performance. Gaussian 09 and Multiwfn 3.8 packages are the software used for calculation, and the electrostatic potentials were depicted using the VMD program. In this study, the imidazole and pyrazole derivatives were optimized at the B3PW91/6-311G (d, p) level to acquire the relevant data for the compounds.

Robust self-healing capacity and high mechanical properties of castor oil-based waterborne polyurethane based on “kill two birds with one stone” strategy

Achieving ideal combination of high self-healing efficiency and good mechanical properties is of significance for the breakthrough in the application of self-healing materials. Herein, the functionalized castor oil-based waterborne polyurethane (DA-CWPU) was constructed based on “killing two birds with one stone” molecular design strategy with the addition of self-healing monomer D-A adduct. Firstly, D-A adduct containing flexible D-A bonds and rigid ring structure was prepared by D-A reaction with furfuryl alcohol (FA) and bismaleimide (BMI) as raw materials, which could not only effectively enhanced the self-healing ability of the material, but also ensured the strong mechanical properties. Then, DA-CWPU emulsion with favourable self-healing and mechanical properties was synthesized by the polymerization of castor oil (CO), isophorone diisocyanate (IPDI) and D-A adduct. The DA-CWPU film has preferable self-healing efficiency (93 % at 100 °C for 50 min), unique shape memory effect (rehabilitate after heating at 100 °C for 45 s), good toughness (485 MJ/m3), strong tensile strength (5.96 MPa) and sufficient elongation (115 %). At the same time, the self-healing DA-CWPU film can be recycled through solution casting. The sustainable castor oil-based waterborne polyurethane can be used as finishing agents for leather products, which realizes repeatedly self-healing in case of surface damage, greatly increasing the service life of the material and mechanical properties, providing a new approach for the development of mechanically robust self-healing materials.

Robust Sandwich‐Structured Thermally Activated Delayed Fluorescence Molecules Utilizing 11,12‐Dihydroindolo[2,3‐a]carbazole as Bridge

AbstractConstructing folded molecular structures is emerging as a promising strategy to develop efficient thermally activated delayed fluorescence (TADF) materials. Most folded TADF materials have V‐shaped configurations formed by donors and acceptors linked on carbazole or fluorene bridges. In this work, a facile molecular design strategy is proposed for exploring sandwich‐structured molecules, and a series of novel and robust TADF materials with regular U‐shaped sandwich conformations are constructed by using 11,12‐dihydroindolo[2,3‐a]carbazole as bridge, xanthone as acceptor, and dibenzothiophene, dibenzofuran, 9‐phenylcarbazole and indolo[3,2,1‐JK]carbazole as donors. They hold outstanding thermal stability with ultrahigh decomposition temperatures (556–563 °C), and exhibit fast delayed fluorescence and excellent photoluminescence quantum efficiencies (86 %–97 %). The regular and close stacking of acceptor and donors results in rigidified molecular structures with efficient through‐space interaction, which are conducive to suppressing intramolecular motion and reducing reorganized excited‐state energy. The organic light‐emitting diodes (OLEDs) using them as emitters exhibit excellent electroluminescence performances, with maximum external quantum efficiencies of up to 30.6 %, which is a leading value for the OLEDs based on folded TADF emitters. These results demonstrate the proposed strategy of employing 11,12‐dihydroindolo[2,3‐a]carbazole as bridge for planar donors and acceptors to construct efficient folded TADF materials is applicable.

Advances in Molecular Photoswitches: From Azobenzenes to Azoquinolines

Molecular photoswitches represent a dynamic and ever-growing research area based on the ability of molecules to convert (switch) between cis- (Z) and trans- (E) isomers. Azobenzenes are the most popular and widely employed Z-E photoswitchable molecules in the development of photoresponsive, multifunctional smart materials for various applications. The promising avenues in this field include molecular fine-tuning of azobenzene- based photoswitches and the creation of single or dual-functional probes. This short overview highlights recent advances in the design of molecular photoswitches, particularly the molecular design strategies of azobenzene-based photoswitches with their structural and electronic features. Particular attention is paid to azoquinolines, which seem to be a promising alternative to azobenzenes in the design of novel multifunctional photoswitches with improved photochromic properties. Here, we have also developed the novel star-shaped multiazoquinoline photoswitch comprising individual azoquinoline-based photochromes connected to a central trisubstituted 1,3,5-triformylphloroglucinol core by quantum chemical calculations. This unique structure is favorable for independent Z-E isomerization of each azoquinoline-based photochrome within one macromolecule.