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steric hindrance effect of Schiff-base ligands on magnetic relaxation dynamics and emissive behavior of two dinuclear dysprosium complexes

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Journal of Rare Earths 2023年第7期41卷 1049-1057,I0003页

作者： Youdong Jiang Sourav Dey Hongshan Ke Yongsheng Yang Lin Sun Gang Xie Sanping Chen Gopalan Rajaraman Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education College of Chemistry and Materials ScienceNorthwest UniversityXi'an 710127China Department of Chemistry Indian Institute of Technology BombayPowaiMumbai400076India State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China Henan Key Laboratory of Polyoxometalate Chemistry Institute of Molecular and Crystal EngineeringCollege of Chemistry and Chemical EngineeringHenan UniversityKaifeng 475004China

The self-assembly reactions between mixed-ligand and tetrahydrate dysprosium acetate in the presence of mixed organic solvents lead to two structural similar dinuclear dysprosium complexes with composition formulas of Dy_(2)(L_1)_(2)(L_(2))_(2)(CH_(3)OH)_(2)·CH_(2)Cl_(2)·CH_(3)OH(1) and Dy_(2)(L_1)_(2)(L_(3))_(2)(CH_(3)OH)_(2)·CH_(3)CN(2),where L_1,L_(2) and L_(3) represent the deprotonated form of 4-tert-butyl-2-(7-methoxybenzo[d]oxazol-2-yl)phenol,(E)-1-(((3,5-di-tert-butyI-2-hydroxyphenyI)imino)methyl)naphthalen-2-ol and(E)-2,4-di-tertbutyl-6-((2-hydroxybenzylidene)amino)phenol.The tiny difference of the core structure of 1 and 2 is derived from the steric hindrance of Schiff base ligands L_(2) and L_(3).Dynamic magnetic measurements reveal that 1 and 2 show frequency-dependent out-of-phase alternating-current susceptibility signal peaks at different temperatures under zero dc field,diagnostic of single-molecule magnet behavior.The experimental derived energy barrier to magnetization reversal for 1 and 2 is 108(1),47(2) and 33(3) K.Ab initio CASSCF calculations performed on 1 and 2 suggest that the origin of the difference in magnetic properties originates from the variation in the single-ion anisotropy that arises due to minor structural variation.Further,the equation to calculate the effective energy barrier for Dy_(2) proposed earlier is found to yield an excellent agreement with the experimental results.Solid state fluorescence measurements performed on 1 and 2 demonstrate that both exhibit two ligands centered components of fluorescent emissive,in addition,with different emitting colors and chromaticity coordinates.The discrepancy of fluorescence and single molecule magnet behavior showed by 1 and 2 can be attributed to the steric hindrance effect of Schiff base ligands.

关键词： Fluorescent single-molecule magnets Dinuclear dysprosium complexes Mixed ligand steric hindrance Theoretical calculations Rare earths

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steric hindrance Ligand Strategy to Aluminum Porphyrin Catalyst for Completely Alternative Copolymerization of CO_2 and Propylene Oxide

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Chinese Journal of Polymer Science 2018年第2期36卷 252-260页

作者： Chun-Wei Zhuo Yu-Sheng Qin Xian-Hong Wang Fo-Song Wang Key Laboratory of Polymer Ecomaterial Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China University of Science and Technology of China Hefei 230026China

Aluminum porphyrin complexes are heavy-metal-free and soil-tolerant green catalysts for the copolymerization of CO2 and propylene oxide（PO）, but they suffer from relatively poor poly（propylene carbonate）（PPC） selectivity. Herein, steric hindrance porphyrin ligand was used to enhance the PPC selectivity. Typically, a bulky anthracene-like group was incorporated into the porphyrin ring to form 5,10,15,20-tetra（1,2,3,4,5,6,7,8-octahydro-1,4：5,8-dimethanoanthracen-9-yl）porphyrin, the aluminum porphyrin complex with this ligand, in combination with bis（triphenylphosphine）iminium chloride as a co-catalyst, produced completely alternate PPC. Additionally, the obtained PPC showed high regioselectivity, with a head-to-tail linkage content（HT） of 92%. Therefore, we demonstrated that introduction of bulky steric ligand into the porphyrin ring could reduce the propylene oxide homopolymerization activity leading to excellent PPC selectivity, and improve regioselectivity for the PO ring-opening during the copolymerization.

关键词： Carbon dioxide Propylene oxide Porphyrin Aluminum steric hindrance

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Size matters:steric hindrance of precursor molecules controlling the evolution of CdSe magic-size clusters and quantum dots

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Nano Research 2022年第9期15卷 8564-8572页

作者： Juan Shen Chaoran Luan Nelson Rowell Yang Li Meng Zhang Xiaoqin Chen Kui Yu Institute of Atomic and Molecular Physics Sichuan UniversityChengdu 610065China Laboratory of Ethnopharmacology Tissue-orientated Property of Chinese Medicine Key Laboratory of Sichuan ProvinceWest China School of MedicineWest China HospitalSichuan UniversityChengdu 610065China Metrology Research Centre National Research Council CanadaOttawaOntario K1A 0R6Canada Engineering Research Center in Biomaterials Sichuan UniversityChengdu 610065China

Little is known about how to precisely promote the selective production of either colloidal semiconductor metal chalcogenide(ME),magic-size clusters(MSCs),or quantum dots(QDs).Recently,a two-pathway model has been proposed to comprehend their evolution;here,we reveal for the first time that the size of precursors plays a decisive role in the selected evolution pathway of MSCs and QDs.With the reaction of cadmium myristate(Cd(MA)2)and tri-n-octylphosphine selenide(SeTOP)in 1-octadecene(ODE)as a model system,the size of Cd precursors was manipulated by the steric hindrance of carboxylic acid(RCOOH)additive.Without RCOOH,the reaction produced both CdSe MSCs and QDs(from 100 to 240℃).With RCOOH,the reaction produced MSCs or QDs when R was small(such as CH3−)or large(such as C6H5−),respectively.According to the twopathway model,the selective evolution is attributed to the promotion and suppression of the self-assembly of Cd and Se precursors,respectively.We propose that the addition of carboxylic acid may occur ligand exchange with Cd(MA)2,causing the different sizes of Cd precursor.The results suggest that the size of Cd precursors regulates the self-assemble behavior of the precursors,which dictates the directed evolution of either MSCs or QDs.The present findings bring insights into the two-pathway model,as the size of M and E precursors determine the evolution pathways of MSCs or QDs,the understanding of which is of great fundamental significance toward mechanism-enabled design and predictive synthesis of functional nanomaterials.

关键词： cadmium selenide(CdSe) magic-size clusters(MSCs) quantum dots(QDs) self-assembly steric hindrance

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The Influence of Various Cationic Group on Polynorbornene Based Anion Exchange Membranes with Hydrophobic Large steric hindrance Arylene Substituent

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Chinese Journal of Polymer Science 2023年第2期41卷 278-287页

作者： Wei Wang Da-Fu Cao Xiao-Wei Sun Li Pan Zhe Ma Yue-Sheng Li Tianjin Key Laboratory of Composite and Functional Materials School of Materials Science and EngineeringTianjin UniversityTianjin300350China

A series of brominated polynorbornene derivatives,including bulky steric hydrophobic groups and highly physical and chemical stable backbones,were synthesized via ring-opening metathesis polymerization and post-functionalized with trimethylammonium(QA),N-methylimidazole(Im),N-methylpyrrolidinium(Pyr)or N-methylpiperidinium(Pip)to construct the entire anion exchange membranes(AEMs).Benefited from prominent phase-separated morphology,PBO-x%-y(x=66,68,70;y=QA,Im,Pyr,Pip)AEMs with ion exchange capacity(IEC)approaching 2.0 meq·g^(−1)exhibited super high hydroxide conductivities.Thereinto,PBO-70%-Pip possessed the highest hydroxide conductivity of 137.3 mS·cm^(−1)at 80℃Moreover,all membranes exhibit low swelling ratio(SR)(the SR of PBO-66%-QA was just 8.6%at 80℃).That is,bulky steric hydrophobic groups play a crucial role in balancing the high hydroxide conductivity and low SR in AEMs.Furthermore,three AEMs(PBO-66%-QA,PBO-68%-Pyr,PBO-70%-Pip)showed good alkaline stability after immersion into 1.0 mol/L NaOH aqueous solution at 80℃for 480 h without any degradation.

关键词： Anion exchange membrane steric hindrance Phase separation Ion conductivity Swelling ratio

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steric hindrance Effect in High-Temperature Reactions

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CCS Chemistry 2020年第6期2卷 460-467页

作者： Xiongzhi Zeng Zongyang Qiu Pai Li Zhenyu Li Jinlong Yang Hefei National Laboratory for Physical Sciences at the Microscale University of Science and Technology of ChinaHefei 230026

High-temperature reactions widely exist in nature.However,they are difficult to characterize either experimentally or computationally.The minimum energy path(MEP)model routinely used in computational modeling of chemical reactions is not justified to describe high-temperature reactions since high-energy structures are actively involved at high temperatures.In this study,we used methane(CH4)decomposition on Cu(111)surface as an example to compare systematically results obtained from the MEP model with those obtained from an explicit sampling of all relevant structures via ab initio molecular dynamics(AIMD)simulations at different temperatures.Interestingly,we found that,for reactions protected by strong steric hindrance effects,the MEP was still followed effectively even at a temperature close to the Cu melting point.In contrast,without such protection,the flexibility of the surface Cu atoms could lead to a significant reduction of the free-energy barrier at a high temperature.Accordingly,some earlier conclusions made about graphene growth mechanisms based on MEP calculations should be revisited.The physical insights provided by this study could deepen our understanding of high-temperature surface reactions.

关键词： high-temperature reaction ab initio molecular dynamics minimum energy path free energy steric hindrance graphene growth

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Tailoring the microstructure and properties of PES/SPSf loose nanofiltration membranes using SPES as a hydrophilic polymer for the effective removal of dyes via steric hindrance and charge effect

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Frontiers of Chemical Science and Engineering 2023年第10期17卷 1555-1567页

作者： Xiaowei Liu Christine Matindi Sania Kadanyo Mengyang Hu Shuqian Yang Gansheng Liu Ran Tao Zhenyu Cui Xiaohua Ma Kuanjun Fang Jianxin Li State Key Laboratory of Separation Membranes and Membrane Processes National Center for International Joint Research on Separation MembranesSchool of Materials Science and EngineeringTiangong UniversityTianjin 300387China Collaborative Innovation Center for Eco-Textiles of Shandong Province Qingdao 266071China Institute for Nanotechnology and Water Sustainability College of Science Engineering and Technology University of South AfricaScience CampusFlorida 1710JohannesburgSouth Africa

Herein,polyethersulfone(PES)and sulfonated polysulfone(SPSf)blend membranes were prepared with addition of sulfonated polyethersulfone(SPES)as a hydrophilic polymer and adipic acid as a porogen via non-solvent induced phase separation method for effective fractionation of dyes based on the influence of steric hindrance and charge effect.Raman spectroscopy and molecular dynamic simulation modeling confirmed that hydrogen bonds between PES,SPSf,SPES,and adipic acid were crucial to membrane formation and spatial arrangement.Further addition of hydrophilic SPES resulted in a membrane with reduced pore size and molecular weight cut-off as well as amplified negative charge and pure water permeance.During separation,the blend membranes exhibited higher rejection rates for nine types of small molecular weight(269.3–800 Da)dyes than for neutral polyethylene glycol molecules(200–1000 Da).This was attributed to the size effect and the synergistic effect between steric hindrance and charge repulsion.Notably,the synergistic impact decreased with dye molecular weight,while greater membrane negative charge enhanced small molecular dye rejection.Ideal operational stability and anti-fouling performance were best observed in M2(PES/SPSf/SPES,3.1 wt%).Summarily,this study demonstrates that SPES with–SO3‒functional groups can be applied to control the microstructure and separation of membranes.

关键词： adipic acid loose nanofiltration membrane dye/salt selective separation steric hindrance charge effect

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High-performance nonfused ring electron acceptor with a steric hindrance induced planar molecular backbone

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Science China Chemistry 2022年第3期65卷 594-601页

作者： Hao Lu Xiaodong Wang Hang Wang Andong Zhang Xinming Zheng Na Yu Zheng Tang Xinjun Xu Yahui Liu Ya-Nan Chen Zhishan Bo College of Textiles&Clothing State Key Laboratory of Bio-fibers and Eco-textilesQingdao UniversityQingdao 266071China Beijing Key Laboratory of Energy Conversion and Storage Materials College of ChemistryBeijing Normal UniversityBeijing 100875China Center for Advanced Low-Dimension Materials State Key Laboratory for Modification of Chemical Fibers and Polymer MaterialsCollege of Materials Science and EngineeringDonghua UniversityShanghai 201620China

Three nonfused ring electron acceptors (NFREAs) TTC6,TT-C8T and TT-TC8 were purposefully designed and synthesized.The molecular geometry can be adjusted by the steric hindrance of lateral substituents.According to the DFT calculations,from TTC6 to TT-C8T and TT-TC8,planarity of the molecular backbone is gradually improved,accompanying with the enhancing of intramolecular charge transfer effect.As for TT-TC8,the two phenyl substituents are almost perpendicular to the molecular backbone,which endues the acceptor with good solubility and suppresses it to form over-aggregation.Multidirectional regular molecular orientation and closer molecular stacking are formed in TT-TC8 film.As a result,TT-TC8 based devices afford the highest PCE of 13.13%,which is much higher than that of TTC6 (4.41%) and TT-C8T (10.42%) and among the highest PCE values based on NFREAs.

关键词： organic solar cells nonfused ring electron acceptors nonfullerene acceptors steric hindrance

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Carbazole-endcapped Spiro[fluorene-9,9＇-xanthene] with Large steric hindrance as Hole-transporting Host for Heavily-doped and High Performance OLEDs

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Chinese Journal of Chemistry 2015年第8期33卷 955-960页

作者： Xianghua Zhao Yukun Wu Nannan Shi Xiaoyu Li Yi Zhao Mingli Sun Dongxue Ding Hui Xu Linghai Xie College of Chemistry and Chemical Engineering Xinyang Normal University Xinyang Henan 464000 China State Key Laboratory on Integrated Optoelectronics College of Electronics Science and Engineering Jilin University 2699 Qianjin Street Changchun Jilin 130012 China China Key Laboratory for Organic Electronics & Information Displays (KLOEID) Institute of Advanced Materials (IAM) Nanjing University of Posts & Telecommunications Nanjing Jiangsu 210046 China Key Laboratory of Functional Inorganic Material Chemistry Ministry of Education Heilongjiang University Harbin Heilongjiang 150080 China

In this work, we designed and synthesized a novel spirocyclic compound functionalized spiro[fluorene-9,9＇- xanthene] with carbazole group （2-carbazolyl-spiro[fluorene-9,9＇-xanthene], SFX-Cz） via Friedel-Crafts and Ullmann reaction, which is expected to own high thermal and morphological stability, and good carrier injection/ transporting properties due to the excellent hole transporting characteristics of carbazole and cruciform structure of spiro[fluorene-9,9＇-xanthene]. The carbazole end-capped spiro[fluorene-9,9＇-xanthene] SFX-Cz based PhOLEDs with Flrpic as phosphor emitter have been researched by varying dopant concentration, which exhibit the maximum EQEs of 8.9%, 7.4%, 9.1%, and 4.7% with the doping increasing from 10% to 50%. The higher performance PhOLEDs are independent on concentration variation from 10% to 30%, which suggests the bulky steric hindrance of SFX-Cz might be a potential canditate for high performance and inexpensive device with simplified process.

关键词： steric hindrance spirocyclic compound heavily-doped PhOLEDs inexpensive device

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A novel pyridinylfluorene/triphenylamine hybrid with large steric hindrance used as host material for heavily-doped PhOLEDS

A novel pyridinylfluorene/triphenylamine hybrid with large s...

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河南省化学会2016年学术年会

作者： Li Min Wang Xiao Sheng Li xiang Hua Zhao College of Chemistry and Chemical Engineering Xinyang Normal University

Phosphorescent organic light-emitting diodes(Ph OLEDs) are outstanding science the potential of100% internal quantum resulted from strong spin–orbit coupling caused by heavy atoms, which could lead to an efficient intersystem crossing to harvest both triplet and singlet excitons. However, phosphor emitters often suffer self-quenching and triplet-triplet annihilation at high doping concentration.Ph OLEDs often employ host-guest system to resolve this problem. To date, triphenylamine(TPA) and carbazole derivatives are most widely employed as host materials for Ph OLEDs due to their high triplet energy level, sufficient hole transporting property, and wide energy gap. Nevertheless, the twisted molecule struture of TPA is detrimental to obtain high thermal and morphological stabilities host materilas. Therefore, many efforts have been made to improve thermal and morphological stabilities with high triplet energy level of the TPA host.Although many TPA containing hosts used for Ph OLEDs with high performance at low dopi ng ratios have been reported, rare TPA containing hosts with wide heavy dopant range for stab le perfor-mance Ph OLEDs have been reported due to the inherent triplet–triplet annihilation and concentration quenching of phosphorescent emitters. The low dopant Ph OLEDs could suppress triplet–triplet annihilation and concen-tration quenching of phosphor guests in solid state but und ergo time-consuming and tedious process. Moreover, the slight fluctuation of doping ratio proba bly leads to an obvious change of device performance, which would increase the process diffic ulty and production cost, and reduce device repeatability. In order to resolve this problem, one of the effective strategies is to design and synthesize bulky host with large steric hin-drance to simplify fabrication process and improve device repeatability. In this paper, we demonstrate the facile synthesis of a novel 9-(pyridyl-2-yl)-fluoren-9-ol(Py FOH)/triarylamine hybrid(tris[4-(9-(py ridine-2-yl)-fluoren-9-yl)phenyl]- amine, TPy FTPA)

关键词： steric hindrance triphenylamine PhOLEDs high doping concentration

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Decarboxylative Amination with Nitroarenes via Synergistic Catalysis

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Chinese Journal of Chemistry 2024年第4期42卷 351-355页

作者： Meiling Ding Sitian Zhou Shunruo Yao Chengjian Zhu Weipeng Li Jin Xie State Key Laboratory of Coordination Chemistry Jiangsu Key Laboratory of Advanced Organic MaterialsChemistry and Biomedicine Innovation Center(ChemBIC)School of Chemistry and Chemical EngineeringNanjing UniversityNanjingJiangsu210023 China Green Catalysis Center and College of ChemistryZhengzhou UniversityZhengzhouHenan450001 China

In this paper,we have developed a decarboxylative amination of carboxylic acids with nitroarenes for the synthesis of secondary amines.The protocol is performed at mild conditions without the use of noble metals as catalysts.A wide range of structurally diverse secondary amines could be obtained in good yields(up to 94%)with good functional group tolerance.This transformation shows good to excellent selectivity,avoiding the generation of over alkylated byproducts.

关键词： Nitroarenes Amines Synergistic catalysis Carboxylic acids Radical alkylation Amination Photocatalysis steric hindrance

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