Temperature-Driven Axial-Equatorial Isomerism and Magnetic Relaxation on Low-Spin Co(Ⅱ)Borohydride Complexes  

作　　者：Jing-Yu Wang Zhen Li Lu Zhang Yan-Cong Chen Ze-Yu Ruan Shan-Nan Du Wei Deng Si-Guo Wu Jun-Liang Liu Ming-Liang Tong 

机构地区：[1]KeyLaboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education,School of Chemistry,IGCME,GBRCE for Functional Molecular Engineering,SunYat-Sen University,Guangzhou,Guangdong 510275,China

出　　处：《Chinese Journal of Chemistry》2025年第4期423-430,共8页中国化学(英文版)

基　　金：supported by the NSFC(Grant Nos.22475246,22105230 and 21821003);the Fundamental Research Funds for the Central Universities;Sun Yat-sen University(24xkjc003 and 24qnpy051).

摘　　要：Crystalline materials with diastereomerism serve as ideal prototypes for investigating the influence of coordination environments on chemophysical properties.In this study,we synthesized a pair of axial-equatorial isomers[Co(Ⅱ)(HB(tim^(tBu))_(3))(cis-dppen)](BF_(4))·solv([HB(tim^(tBu))_(3)]^(-)=hydrotris(3-tertbutyl-2-thioxoimidazol-1-yl)borate;cis-dppen=cis-1,2-bis(diphenylphosphino)ethene;solv=0.5THF·2H_(2)O and 2H_(2)O for ax-CoHS_(2)P_(2) and eq-CoHS2P2,respectively),by varying the crystallization temperatures.Despite both diastereoisomers adopting distorted square pyramidal geometries,the bidentate cis-dppen ligand chelates to the central Co(Ⅱ)either in an axial-equatorial or equatorial-equatorial manner,with a boron-hydrogen binding to the metal center.Magnetic studies reveal differences in g-values between these axial-equatorial isomers.X-band electron paramagnetic resonance spectra suggest rapid equilibrium and potential conformational interconversion in response to temperature changes in solution.Magnetic measurements indicate field-induced slow relaxation of magnetization in this low-spin S=1/2 system,with spin-lattice relaxations dominated by Raman and quantum tunneling of magnetization mechanisms due to the absence of thermally populated excited states.

关 键 词：Metal borohydride complexes Axial-equatorial isomerism Low spin Magnetism STEREOCHEMISTRY Crystal structure ISOMERS 

分 类 号：O62[理学—有机化学]