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Study on fluorescence properties of rare earth complexes influenced by steric effect

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Journal of Rare Earths 2011年第11期29卷 1013-1017页

作者：袁伟崔玉民师瑞娟陶栋梁王永忠张文保陈继堂孙林刘少轩徐怡庄 College of Chemistry and Chemical Industry Fuyang Normal College Anhui Provincial Key Laboratory for Degradation and Monitoring of Pollution of the Environment College of Chemistry and Molecular Engineering Peking University

The rare earth complexes Tb（o-BrBA）3,Tb（m-BrBA）3 and Tb（p-BrBA）3 were synthesized using o-,m-,p-bromo benzoic acids（2-bromo benzoic acid,3-bromo benzoic acid and 4-bromo benzoic acid） as ligand,*** UV spectra showed that the absorption ability of Tb（m-BrBA）3 was the ***,the fluorescent intensity of Tb（o-BrBA）3 was the *** effect of the molecular structure,the energy level of Tb3＋ and energy transfer efficiency from ligands to Tb3＋ were discussed to explain the experimental *** results indicated that,due to the large atomic radius of bromine,the steric effect caused by the different substitution bromine on the benzene ring might strongly affect the bond length formed by the coordination atoms and Tb3＋.The longer the bond length was,the lower the efficiency of energy transfer was,and the weaker the fluorescent intensity was.

关键词： terbium complexes bromo benzoic acid steric effect fluorescent spectrum rare earths

Single molecular insight into steric effect on C-terminal amino acids with various hydrogen bonding sites

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Chinese Chemical Letters 2022年第10期33卷 4649-4654页

作者： Yunzhi Xie Chunhua Liu Linxiu Cheng Yulan Fan Huifang Li Wei Liu Lei Zhu Xun Li Ke Deng Qingdao Zeng Shoufa Han State Key Laboratory for Physical Chemistry of Solid Surfaces Department of Chemical BiologyCollege of Chemistry and Chemical EngineeringThe Key Laboratory for Chemical Biology of Fujian ProvinceThe MOE Key Laboratory of Spectrochemical Analysis&Instrumentationand Innovation Center for Cell Signaling NetworkXiamen UniversityXiamen 361005China Jiangxi Provincial Key Laboratory of Low-Carbon Solid Waste Recycling School of Geography and Environmental EngineeringGannan Normal UniversityGanzhou 341000China Jiangxi Key Laboratory of Organo-Pharmaceutical Chemistry Chemistry and Chemical Engineering CollegeGannan Normal UniversityGanzhou 341000China CAS Key Laboratory of Standardization and Measurement for Nanotechnology CAS Center for Excellence in NanoscienceNational Center for Nanoscience and Technology(NCNST)Beijing 100190China

Amino acids are basic units to construct a protein with the assistance of various *** this building process,steric hindrance derived from amino acid side groups or side chains is a factor that could not be *** this contribution,adsorption behaviors of C-terminal amino acid derivatives with amino acid residues fused in 3,4,9,10-perylenetetracarboxylic dianhydride were investigated by scanning tunneling microscopy(STM)and density functional theory(DFT)calculations at various liquid/solid *** results at 1-phenyloctane/HOPG interface show that N,N'-3,4,9,10-perylenedicarboximide(GP)and N,N'-methyl-3,4,9,10-perylenedicarboximide(AP)formed linear and herringbone structures,*** driving force could be attributed to different H-bonding sites induced by steric hindrance at side groups.N,N'-Benzyl-3,4,9,10-perylenedicarboximide(PP)generates both linear and herringbone structures because steric hindrance changes the H-bonding sites between PP molecules,whereas N,N'-isopropyl-3,4,9,10-perylenedicarboximide(LP)failed to be imaged because of strong steric hindrance coming from larger side *** further investigate the impact of steric hindrance,we utilized octanoic acid(OA)as solvent to capture the adsorption details of LP and *** found that OA molecules drag PP and LP molecules in a different direction to generate linear structure,impeding the molecular *** structure–solvent relationship shows that the steric hindrance is brought by the large side group,which makes it easier to recognize OA molecules at the *** results demonstrate that steric effect plays a significant role in altering interaction sites of the compounds during the adsorption process at the liquid/solid interface.

关键词： C-terminal amino acids steric effect Bonding site Scanning tunneling microscopy DFT calculations

Quantifying Electrophilicity and steric effect with DFT

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Quantifying Electrophilicity and Steric Effect with DFT

steric effects in the Cl＋CHD3（v1=1） Reaction

中国化学会第26届学术年会理论化学方法和应用分会场

作者： Shubin Liu Renaissance Computing Institute, University of North Carolina, Chapel Hill, North Carolina 27599-3455, USA

＜正＞Theoretical justification for explicitly quantifying traditional chemical concepts such as electrophilicity, nucleophilicity, and steric effect within the conceptual framework of density functional theory will b... 详细信息

关键词： Keywords: electrophilicity nucleophilicity steric effect DFT.

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Chinese Journal of Chemical Physics 2013年第6期26卷 705-709,I0004页

作者： Fengyan Wang Kopin Liu Institute of Atomic and Molecular Sciences Academia Sinica P. O. Box 23-166 Taipei 10617 Taiwan Department of Chemistry Fudan University Shanghai 200433 China

A recent study has revealed a full 3-dimentional reactive scattering picture of the reaction CI＋CHD3（v1=1） as the C1 atoms attack CHD3 from various directions respective to the C-H stretching bond. The reported polarization-dependent differential cross sections provide the most detailed characterization of the influences of reagent alignments on reactivity. To convey the stereo-specific information more accessible to general chemists, we show here, by proper symmetry considerations, how to retrieve from the measurements the relative integral and differential cross sections of two most common collision geometries： the end-on versus side-on attacks. The results, albeit coarse-grained, provide an appealing picture that not only reinforces our intuition about chemical reactivity, but also sheds more light on the conventional （unpolarized） attributes.

关键词： steric effect Integrate cross section Cylindrical symmetry Slice image Crossed beam technique

Structural tailoring of covalent organic frameworks with steric effects

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Science China Chemistry 2023年第11期66卷 2977-2985页

作者： Guiqing Lin Arindam Mal Xuejiao Wang Xu Zhou Bo Gui Cheng Wang College of Chemistry and Molecular Sciences Wuhan UniversityWuhan 430072China

Covalent organic frameworks(COFs)provide a unique platform with tunable structures allowing precise control of pore sizes,shapes and *** key to synthesizing COFs with desired structures is to precisely control the conformation and geometry of building blocks as well as the growth direction of *** achieve this,steric effects are noteworthy that may have a significant impact on the assembly of ***,the introduction of sterically demanding substituents or bulky groups into monomers of COFs will lead to intramolecular conformational changes and intermolecular repulsions,which induce structural changes in COFs,including changes in torsion angles,interlayer distances,stacking modes and topologies of 2D COFs,and changes in spatial nodes,interpenetration and topologies of 3D *** review will help to understand the impacts of steric effects on the structures of COFs and to take them into extensive consideration in the design and synthesis of COFs with novel functionalities and structural attributes.

关键词： covalent organic frameworks steric effect structural tailoring

Ligand steric effects on Naphthyl-α-diimine Nickel Catalyzed α-Olefin Polymerization

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Chinese Journal of Polymer Science 2018年第2期36卷 157-162页

作者： Fu-Zhou Wang Su-Su Tian Rui-Ping Li Wei-Min Li Chang-Le Chen Advanced Catalysis and Green Manufacturing Collaborative Innovation Center School of Pertrochemical Engineering Changzhou University Chinese Academy of Sciences Key Laboratory of Soft Matter Chemistry Department of Polymer Science and Engineering University of Science and Technology of China

Naphthyl-α-diimine nickel complexes with systematically varied ligand sterics, activated by modified methylaluminoxane（MMAO）, were tested in the polymerization of higher α-olefin（1-hexene, 1-decene and 1-hexadecene） under suitable conditions. The polymerization results indicated the possibility of precise microstructure control, depending on catalyst structure, polymerization temperature, monomer concentration and types of monomers, which in turn strongly affects the resultant polymer properties. Naphthyl-α-diimine nickel complex bearing chiral bulky sec-phenethyl groups in the o-naphthyl position showed good catalytic activity, and resulted in branched polymers（42-88/1000 C） with high molecular weights（Mn：（4.3-15.2） × 10^4 g·mol^-1） and narrow molecular weight distribution（Mw/Mn = 1.13-1.29, RT）, which suggested a living polymerization. The increasing steric hindrance of catalyst leads to enhance insertion for 2,1-insertion of α-olefin and the chain-walking reaction.

关键词： Naphthyl-α-diimine nickel complex Chain-walking polymerization Higher α-olefin steric effect

Progress in Fluorene-based Wide-bandgap steric Semiconductors

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Chinese Journal of Polymer Science 2017年第2期35卷 155-170页

作者： Meng-na Yu Chang-jin Ou Bin Liu Dong-qing Lin Yu-yu Liu Wei Xue Zong-qiong Lin Jin-yi Lin Yan Qian Sha-sha Wang Hong-tao Cao Lin-yi Bian 解令海黄维 Center for Molecular Systems and Organic Devices (CMSOD) Key Laboratory for Organic Electronics and Information Displays ＆ Institute of Advanced Materials (IAM) Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM) Nanjing University of Posts ＆ Telecommunications Nanjing 210023 China Key Laboratory of Flexible Electronics (KLOFE) ＆ Institute of Advanced Materials (IAM) Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM) Nanjing Tech University (Nanjing Tech) Nanjing 211816 China

Molecular bulks are favorable for the thermal and morphological stability in organic wide-bandgap semiconducting polymers with potential applications in both information and energy electronics. In this review, we present our progress in the design of fluorene-based bulky semiconductors with a fractal four-element pattern. Firstly, we established one-pot methods to spirofluorenes, especially spiro[fluorene-9,9＇-xanthene] （SFX） serving as the next-generation spiro-based semiconductors. Secondly, we observed the supramolecular forces at the bulky groups and discovered the supramolecular steric hindrance （SSH） effect on polymorphisms, nanocrystals as well as device performance. Thus, a synergistically molecular attractor-repulsor theory （SMART） was proposed for the control of nanocrystal morphology, thin film phase and morphology. Thirdly, the third possible type of defects has been identified to generate green band （g-band） emission in wide- bandgap semiconductors by the introduction of molecular strain design of cyclofluorene. Finally, the first bulky polydiarylfluorene with highly crystalline and β conformation was achieved by an attractor-repulsor design of tadpole-shape monomer, which offered an effective platform to fabricate stable wide-bandgap semiconducting devices. All the discoveries offer the solid basis to break through bottlenecks of organic/polymer wide-bandgap semiconductors by the improvements of overall performances.

关键词： Organics steric effect Attractor-repulsor Molecular defects Wide-bandgap

Styrene-containing Phosphine-sulfonate Ligands for Nickel-and Palladium-catalyzed Ethylene Polymerization

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Chinese Journal of Polymer Science 2021年第4期39卷 447-454,I0006页

作者： Shabnam Behzadi Chen Zou Bang-Pei Yang Chen Tan Chang-Le Chen Chinese Academy of Sciences Key Laboratory of Soft Matter Chemistry Hefei National Laboratory for Physical Sciences at the MicroscaleDepartment of Polymer Science and EngineeringUniversity of Science and Technology of ChinaHefei 230026China Institutes of Physical Science and Information Technology Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of EducationAnhui UniversityHefei230026China

A series of phosphine-sulfonate ligands bearing 2-,3-and 4-vinylphenyl on the phosphorus atom were designed,synthesized,characterized and investigated in Ni-and Pd-catalyzed ethylene *** structure of the phosphine-sulfonate Pd complex bearing 2-vinylphenyl on the phosphorus atom showed 2,1-insertion for the 2-vinyl *** phosphine-sulfonate Ni complex bearing 2-vinylphenyl resulted in significantly increased thermal stability and polyethylene molecular weights(Mn=3.69×10^(4)g·mol^(-1) at 80℃)versus the counterparts bearing 3-/4-vinyl groups as well as previously reported phosphine-sulfonate Ni complexes bearing bulky biaryl substituents.

关键词： Phosphine-sulfonate Ethylene polymerization steric effect Palladium Nickel

Multiple effects Tailoring the Self-organization Behaviors of Triphenylene Side-chain Liquid Crystalline Polymers via Changing the Spacer Length

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Chinese Journal of Polymer Science 2018年第8期36卷 960-969页

作者： Xiang-Hui Han Xi-Wen Yang Sheng Chen Hang Luo Dou Zhang Hai-Liang Zhang Key Laboratory of Polymeric Materials and Application Technology of Hunan Province Key Laboratory of Advanced Functional Polymer Materials of Colleges and Universities of Hunan ProvinceCollege of ChemistryXiangtan University State Key Laboratory of Powder Metallurgy Central South University

Long-alkyl tail triphenylene （TP） side-chain liquid crystalline polymers （SCLCPs） with different spacer length （P-m-TP, m = 2, 3, 4, 6, 8, which is the number of carbon atom in the flexible alkyl spacers） have been successfully synthesized via free radical polymerization. The differential scanning calorimetry （DSC）, polarized light microscopy （POM）, ultraviolet-visible spectroscopy （UV- Vis）, wide-angle X-ray diffraction （WAXD） and small-angle X-ray scattering （SAXS） measurements were performed to investigate the influence of multiple effects on the self-organization behaviors of P-m-TP, including steric effect, decoupling effect and π-π stacking effect. The experimental results revealed that P-m-TP （m = 2, 3, 4） formed the columnar phase which was developed by the TP moieties and the main chain as a whole, suggesting that the side-chains had strong steric effect even though the number of spacer length （m） exceeded 4. In addition, the clearing points （Tis） of the polymers were above 300 ℃. When m = 6 and 8, the polymers displayed hexagonal columnar phase and exhibited the low Tis （91 and 80 ℃ respectively）, originating from the self-assembly of triphenylene due to the decoupling effect and π-π stacking effect. This work offers a viable and inspiring pathway to control the phase transition temperature and phase structure ofTP SCLCPs via simply tailoring the spacer length and increasing the alkyl tail length of TP.

关键词： Polymer synthesis Side-chain liquid crystalline polymers Phase structure steric effect