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Improving Efficiency of Red Thermally Activated Delayed Fluorescence Emitter by Introducing Quasi-Degenerate Orbital Distribution

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Chinese Journal of Chemistry 2022年第8期40卷 911-917页

作者： Hao-Yu Yang Ming Zhang Jue-Wen Zhao Chun-Peng Pu Hui Lin Si-Lu Tao Cai-Jun Zheng Xiao-Hong Zhang School of Optoelectronic Science and Engineering University of Electronic Science and Technology of ChinaChengduSichuan 610054China Institute of Functional Nano&Soft Materials(FUNSOM) Soochow UniversitySuzhouJiangsu 215123China

Red thermally activated delayed fluorescence(TADF)emitters are essential for the development of organic light-emitting diodes(OLEDs).To better understand and develop red TADF emitters,herein,the effect of quasi-degenerate orbital distribution was inves-tigated on their performance.Two red TADF emitters 10,10'-(11,12-difluorodibenzo[a,c]phenazine-3,6-diyl)bis(10H-phenoxazine)(DPXZ-BPF)and 10,10',10"-(12-fluorodibenzo[a,c]phenazine-3,6,11-triyl)tris(10H-phenoxazine)(TPXZ-BPF)were constructed by combining two or three phenoxazine(PXZ)donor units with a rigid coplanar acceptor core.As expected,a couple of PXZ units can induce quasi-degenerate orbital distribution by virtue of the high steric hindrance between each donor unit and acceptor core,which enables multiple excited states engaged in the reverse intersystem crossing(RISC)process.Consequently,DPXZ-BPF and TPXZ-BPF exhibit fast RISC rates(k_(RISCs))of 1.07×10^(6) s^(-1) and 1.29×10^(6) s^(-1) and high PLQYs of 74.6% and 81.1%,respectively.And the higher kRISC and PLQY of TPXZ-BPF are mainly attributed to the additional quasi-degenerate orbitals,which further enhance the tri-plet RISC process and the singlet radiative process.As a result,TPXZ-BPF-based OLEDs achieved improved efficiencies with a red-shifted emission compared with DPXZ-BPF-based OLEDs.These results demonstrated the tremendous potential of introducing quasi-degenerate orbital distribution in developing red TADF emitters.

关键词： Organic light-emitting diodes Quasi-degenerate orbital distribution Density functional calculations Molecular dynamics steric hindrance

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Stabilizing photo-induced vacancy defects in MOF matrix for highperformance SERS detection

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Nano Research 2022年第6期15卷 5347-5354页

作者： Hongzhao Sun Ge Song Wenbin Gong Weibang Lu Shan Cong Zhigang Zhao School of Nano-Tech and Nano-Bionics University of Science and Technology of ChinaHefei 230026China Key Lab of Nanodevices and Applications Suzhou Institute of Nano-Tech and Nano-BionicsChinese Academy of SciencesSuzhou 215123China Key Laboratory of Multifunctional Nanomaterials and Smart Systems Chinese Academy of SciencesSuzhou 215123China Division of Nanomaterials Suzhou Institute of Nano-Tech and Nano-BionicsChinese Academy of SciencesNanchang 330200China School of Physics and Energy Xuzhou University of TechnologyXuzhou 221018China

Photo-induced vacancy defects are employed strategically to imbue semiconductors with enhanced performance characteristics for many important applications such as surface-enhanced Raman scattering(SERS)sensing,photocatalysis,and photovoltaic applications.However,the long-term maintenance and use of photo-induced vacancy defects remain elusive,because of their rapid self-healing upon air exposure.In this study,we demonstrate that photo-induced oxygen vacancy(PIVO)defects can be stabilized by the photoexcitation of metal–organic framework(MOF)materials,which is crucial for SERS analysis.The PIVO defects in MOF materials are stable for at least two weeks in the ambient atmosphere,owing to the combination of steric hindrance and electron delocalization around vacancy defects,which significantly contrasts the short lifetime(within minutes)of PIVO defects in metal-oxide semiconductors.With the formation of stable PIVO defects,a prominent SERS enhancement surpassing that of pristine MOFs is achieved,accompanied with a reduced limit of detection by three orders of magnitude.Moreover,the additional SERS enhancement rendered by PIVO defects can be stably retained and is effective for monitoring various small molecules,such as dopamine and bisphenol A.

关键词： stable photo-induced vacancy defects metal−organic framework materials steric hindrance electron delocalization Raman spectroscopy

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Predictably synthesizing a library of white-light-emitting perovskites

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Science China Chemistry 2023年第3期66卷 760-767页

作者： Ludan Niu Lili Zhao Deyu Li Qian Chen Mingming Zhang Jing Luan Lei Wang Weigao Xu Jun Xing Key Laboratory of Eco-chemical Engineering Ministry of EducationCollege of Chemistry and Molecular EngineeringQingdao University of Science&TechnologyQingdao 266042China Key Laboratory of Mesoscopic Chemistry Ministry of EducationSchool of Chemistry and Chemical EngineeringNanjing UniversityNanjing 210023China School of Materials Science and Technology Qingdao University of Science&TechnologyQingdao 266042China Shandong Engineering Research Center for Marine Environment Corrosion and Safety Protection College of Environment and Safety EngineeringQingdao University of Science and TechnologyQingdao 266042China

The low-dimensional organic-inorganic halide perovskites with self-trapped exciton emission have promising prospects for single-phase white-light emitters. However, so far, these broadband white-light-emitting(BWLE) perovskites were synthesized by trial-and-error testing spacing molecules. Here, we developed a steric hindrance regulation strategy to predictably synthesize BWLE perovskites. The molecules containing C–C(–NH_(2))–C groups were introduced into low-dimensional perovskites, which brings a large steric hindrance in-plane orientation. The bigger C–C(–NH_(2))–C bond angle would induce larger structural distortion in perovskites, which leads to the higher rate of self-trapping of excitons and the deeper self-trapping depth. The photoluminescence spectra of the synthesized perovskites can cover the cool-to-warm white light region. Overall, we fabricated a material library consisting of 40 kinds of BWLE compounds according to this strategy. Our findings develop a general strategy to synthesize BWLE perovskites and offer a material platform for optoelectronic applications.

关键词： white-light emission halide perovskite steric hindrance two-dimensional

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Cold plasma-activated Cu-Co catalysts with CN vacancies for enhancing CO_(2)electroreduction to low-carbon alcohol

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Journal of Energy Chemistry 2023年第10期85卷 108-115,I0005页

作者： Junyi Peng Qiang Zhang Yang Zhou Xiaohui Yang Fang Guo Junqiang Xu College of Chemistry and Chemical Engineering Chongqing University of TechnologyChongqing 400054China College of Chemistry and Chemical Engineering Chongqing UniversityChongqing 400044China Chongqing Institute of Green and Intelligent Technology Chinese Academy of SciencesChongqing 4000714China

Electrocatalytic CO_(2)reduction reaction to low-carbon alcohol is a challenging task,especially high selectivity for ethanol,which is mainly limited by the regulation of reaction intermediates and subsequent C–C coupling.A Cu-Co bimetallic catalyst with CN vacancies is successfully developed by H_(2)cold plasma toward a high-efficiency CO_(2)RR into low-carbon alcohol.The Cu-Co PBA-V_(CN)(Prussian blue analogues with CN vacancies)electrocatalyst yields methanol and ethanol as major products with a total low-carbon alcohol FE of 83.8%(methanol:39.2%,ethanol:44.6%)at-0.9 V vs.RHE,excellent durability(100 h)and a small onset potential of-0.21 V.ATR-SEIRAS(attenuated total internal reflection surface enhanced infrared absorption spectroscopy)and DFT(density functional theory)reveal that the steric hindrance of V_(CN)can enhance the CO generation from*COOH,and the C–C coupling can also be increased by CO spillover on uniformly dispersed Cu atoms.This work provides a strategy for the design and preparation of electrocatalysts for CO_(2)RR into low-carbon alcohol products and highlights the impact of catalyst steric hindrance to catalytic performance.

关键词： Cold plasma CN vacancies steric hindrance Bimetallic catalyst Low-carbon alcohol

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The effect of multiple pairs of meta-dicarboxyl groups on molecular self-assembly and the selective adsorption of coronene by hydrogen bonding and van der Waals forces

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Nano Research 2022年第2期15卷 1691-1697页

作者： Jianqiao Li Wendi Luo Siqi Zhang Chunyu Ma Xunwen Xiao Wubiao Duan Qingdao Zeng CAS Key Laboratory of Standardization and Measurement for Nanotechnology CAS Center for Excellence in NanoscienceNational Center for Nanoscience and Technology(NCNST)Beijing 100190China Department of Chemistry School of ScienceBeijing Jiaotong UniversityBeijing 100044China School of Materials and Chemical Engineering Ningbo University of TechnologyNingbo 315211China

The prediction of two-dimensional molecular self-assembly structures has always been a problem to be solved.The molecules with meta-dicarboxyl groups can self-assemble into a specific hexagonal cavity,which has an important influence on the prediction of molecular self-assembly structures and the application of functional molecules with meta-dicarboxyl groups.Two kinds of molecules with four pairs of meta-dicarboxyl groups,1,3,6,8-tet「akis(3,5-isophthalic acid)pyrene(H_(8)TIAPy)and 4′,4′",4′"",4""-(ethene-1,1,2,2-tetrayl)tetrakis(([1,1′-biphenyl]-3,5-dicarboxylic acid))(H8ETTB)molecules were chosen to observe the self-assembly behavior at the heptanoic acid/highly oriented pyrolytic graphite(HA/HOPG)interface.H8TIAPy molecules self-assembled into well-ordered quadrilateral structures and could be regulated into kagome networks with hexagonal pores by coronene(COR)molecules.H8ETTB molecules self-assembled into lamellar structures and transformed into acid-COR-acid-COR co-assembled structures at low concentration of COR solution and acid-COR dimer-acid-COR dimer co-assembled structures at high concentration of COR solution.The reason that H8ETTB molecules could not be regulated into hexagonal porous architecture was attributed to the steric hindrance by the similar length and width of H8ETTB molecules.The H8ETTB templates had stronger adsorption for COR than that of hexaphenylbenzene(HPB),regardless of the order of molecular introduction.

关键词： meta-dicarboxyl groups hexagonal cavity selective adsorption self-assembly steric hindrance

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Radical-Mediated Selective Functionalization of Unactivated Primary C-H Bonds

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Chinese Journal of Chemistry 2022年第14期40卷 1751-1753页

作者： Zhan-Lin Wang Fei Wang State Key Laboratory of Elemento-Organic Chemistry College of ChemistryNankai UniversityTianjin 300071China

Radical-mediated sp^(3)C—H functionalization has found broad applications in synthesis and late-stage derivatization of complex molecules.The site-selectivity of a given reaction is mainly dictated by the bond strength,polarity and steric accessibility of diverse C—H bonds as well as the characters of hydrogen atom acceptors.Unactivated sp^(3)C—H bonds usually follow the relative reactivity sequence of tertiary>secondary>primary,which is even recognized as the innate preferences of certain substrates.The development of innovative methods capable of overriding the“inherent”site-selectivity is exceedingly attractive.Although it has been demonstrated that secondary C—H bonds could be selectively converted in the presence of weaker tertiary C—H bonds by tuning the steric and electronic properties of hydrogen atom acceptors,the selective activation of primary C—H bonds remains a daunting challenge.Herein,we highlight the recently emerging attempts towards this goal by interrogating the steric effect of hydrogen atom acceptors.

关键词： C-H activation Hydrogen atom transfer Radical reactions Regioselectivity steric hindrance

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Removal of antimonite and antimonate from water using Fe-based metal-organic frameworks: The relationship between framework structure and adsorption performance

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Journal of Environmental Sciences 2019年第12期31卷 213-224页

作者： Wei Zhang Na Li Ting Xiao Wenting Tang Guangli Xiu State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process School of Resources and Environmental EngineeringEast China University of Science and TechnologyShanghai 200237China Shanghai Institute of Pollution Control and Ecological Security Tongji UniversityShanghai 200092China Shanghai Environmental Protection Key Laboratory on Environmental Standard and Risk Management of Chemical Pollutants East ChinaUniversity of Science and TechnologyShanghai 200237China

We investigated the adsorption performance of five Fe-based MOFs(Fe-BTC,MIL-100(Fe),MIL-101(Fe),MIL-53(Fe)and MIL-88 C(Fe))for removal of antimonite(Sb(Ⅲ))and antimonate(Sb(Ⅴ))from water.Among these MOFs,MIL-101(Fe)exhibited the best adsorption capacities for both Sb(Ⅲ)and Sb(Ⅴ)(151.8 and 472.8 mg/g,respectively)which were higher than those of most adsorbents previously reported.The effect of steric hindrance was evident during Sb removal using the Fe-based MOFs,and the proper diameter of the smallest cage windows/channels should be considered an important parameter during the evaluation and selection of MOFs.Additionally,the adsorption capacities of MIL-101(Fe)for Sb(Ⅴ)decreased with increasing initial p H values(from 3.0 to 8.0),while the opposite trend was observed for Sb(Ⅲ).Chloride,nitrate and sulfate ions had a negligible influence on Sb(Ⅴ)adsorption,while NO3-and SO42-improved Sb(Ⅲ)adsorption.This result implies that inner sphere complexes might form during both Sb(Ⅲ)and Sb(Ⅴ)adsorption.

关键词： Metal organic frameworks MIL-lOl(Fe) Antimonite Antimonate Cage windows steric hindrance

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A Bulky Pyridinylfluorene/Triphenylamine Hybrid Used as Host Material for Heavily-Doped Blue Electrophosphorescent Devices

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Chinese Journal of Chemistry 2016年第4期34卷 397-402页

作者： Xianghua Zhao Yukun Wu Li Zhou Nana Wu Lin Tang Yi Zhao Xiaosheng Li Dongxue Ding Hui Xu College of Chemistry and Chemical Engineering Xinyang Normal University Xinyang 464000 Henan China State Key Laboratory on Integrated Optoelectronics College of Electronics Science and Engineering Jilin University Changchun Jilin 130012 China Key Laboratory of Functional Inorganic Material Chemistry Ministry of Education Heilongjiang University Harbin Heilongfiang 150080 China

In this work, a novel molecule pyridinylfluorene/triphenylamine hybrid （TPyFTPA） with bulky steric hindrance effects has been synthesized successfully by substituting 9-（pyridine-2-yl）-fluoren-9-yl with triphenylamine （TPA） via Friedel-Crafts reaction, which possesses good thermal stability and triplet energy （ET） of 420 ℃ with 5% weight loss and 2.86 eV, respectively. Moreover, the bulky steric hindrance material shows high stable morphology by heating to 200 ℃ without finding melting phenomena and crystallization that is demonstrated by differential scanning calorimetry （DSC） curve. The bulky pyridinylfluorene end-capped TPA has been used as host material for blue phosphorescent organic light-emitting diodes （PhOLEDs） with maximum external quantum efficiencies （EQEs） of 2.7%, 3.7%, and 3.5%, at the doping ratios of 10%, 30%, and 40%, respectively. The performances of TPyFTPA-based blue PhOLEDs own wide concentration ranging from 10% to 40%, which indicates the bulky TPyFTPA might be a potential candidate for inexpensive products with simplifying process for the applications in full-color display and solid state lighting.

关键词： steric hindrance triphenylamine PhOLEDs high doping concentration

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Revisiting the Thermosensitivity of Poly(acrylamide-co-diacetone acrylamide)

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Chinese Journal of Polymer Science 2014年第5期32卷 531-539页

作者： Xin-ming Xing Guang-ming Liu Yan-wei Ding 张广照 Hefei National Laboratory for Physical Sciences at the Microscale Department of Chemical Physics University of Science and Technology of China Faculty of Materials Science and Engineering South China University of Technology

The lower critical solution temperature （LCST） behavior of poly（acrylamide-co-diacetone acrylamide）（poly（AM-co-DAM）） copolymer in aqueous solutions was studied. The results demonstrate the LCST linearly decreases as the molar fraction of DAM （fDAM） increases. In the range of fDAM 〈 0.36, the transmittance increases as fDAM decreases because the more hydrophilic copolymer chains can form looser aggregates with a lower refractive index. The transmittance exhibits a minimum when fDAM is less than 0.28 as the chains form micelle-like structure with a size smaller than the wavelength. The LCST decreases with the initial polymer concentration, but it levels off when the polymer concentration is high enough. Moreover, no hysteresis can be observed in the change of transmittance during the heating-cooling process because no additional hydrogen bonds are formed in the collapsed state due to the steric hindrance of the large side groups in DAM units.

关键词： Thermosensitive Aggregation Hydrogen bonds steric hindrance Hysteresis.

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Reactivity of Organolithium Reagents to 2,3,4,5-Tetraphenylcyclopentadienone and Crystal Structures of Addition Products

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Chemical Research in Chinese Universities 2015年第5期31卷 736-741页

作者： ZHANG Xiaoyong HAN Limin ZHU Ning GAO Yuanyuan SUO Quanling Chemical Engineering College Inner Mongolia University of Technology Hohhot 010051 P. R. China Department of Chemistry Baotou Teacher's College Baotou 014030 P. R. China

The conjugate addition reactions of four organolithium reagents to 2,3,4,5-tetraphenylcyclopentadienone （tetracyclone） were investigated to reveal the reactivity of organolithium reagents to tetracyclone. The results show that 1,2-addition products 2,3,4,5-tetraphenyl-1-（2-thienyl）-2,4-cyclopentadien-l-ol（1）, 1-n-butyl-2,3,4,5-tetraphenyl- 2,4-cyclopentadien-l-ol（2） and 1,2,3,4,5-pentaphenyl-2,4-cyclopentadien-1-ol（3） were synthesized in excellent yields while tetracyclone reacted with 2-thienyllithium, n-butyllithium and phenyllithium, respectively. Interestingly, three 1,2-, 1,4- and 1,6-addition isomers 1-tert-butyl-2,3,4,5-tetraphenyl-2,4-cyclopentadien-1-ol（4）, 4-tert-butyl-2,3,4,5- tetraphenyl-2-cyclopenten-1-one（5） and 2-tert-butyl-2,3,4,5-tetraphenyl-3-cyclopenten-1-one（6）, were simultaneously obtained by the conjugate addition reaction of tert-butyllithium with larger steric hindrance to tetracyclone. Compounds 1-6 were characterized by ^1H and ^13C NMR spectra, Fourier transform infrared（FTIR） spectra and mass spectra（MS）. The crystal and molecular structures of compounds 1, 2 and isomers 5, 6 were determined by X-ray single crystal diffraction technique. The results imply that the steric hindrance of tert-butyllithium probably play a key role in controlling the conjugate addition reaction. The conjugate addition mechanism of organolithium reagents to tetracyclone was proposed.

关键词： Conjugate addition reaction 2,3,4,5-Tetraphenylcyclopentadienone Organolithium reagent steric hindrance

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