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 iso...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.展开更多
基金supported by the NSFC(Grant Nos.22475246,22105230 and 21821003)the Fundamental Research Funds for the Central UniversitiesSun Yat-sen University(24xkjc003 and 24qnpy051).
文摘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.
