Construction And Research Of Cyano-Bridged Fe~?/Co~? Spin Transition Complexes

Spin-transition compounds,which show fast response under the external stimuli of light and temperature,have attracted much attention because of their potential application in sensers and memory devices.However,based on the use of molecular engineering to achieve controlled assembly of space structures,it faces many challenges in adjusting the magnetic functions from the perspective of electronic structure and extending the research from the molecular to the electronic level.Around the reversible switch of electronic arrangement and migation in the heterometallic complexes,this dissertation mainly focuses on two parts:the first is utilizing the physical means or chemical means like changing the steric hindrance of ligands to tune the electronic arrangement in the spin crossover(SCO)complexes,further systematical investigation of regulation of the SCO complexes' properties;the second is the incorporation and coupling of magnetism,polarity and thermal expansion via the changes of charge and bond length induced by electron transfer and arrangement in the metal-to-metal charge transfer(MMCT)complexes.The main research results are as follows:(1)Two cyano-bridged dinuclcar SCO compounds of 1 and 2 and four trinuclear SCO compounds of 3-6 were synthesized through self-assembly of paramagnetic tricyanometalate building blocks with different steric hindrance[Bu4N][pzTpFe?(CN)3],[Bu4N][Tp*Fe?(CN)3],[Bu4N][TpMeFe?(CN)3]and[Bu4N][TpFe?(CN)3],pentadentate ligand N-benzyl-N,N',N'-tris(2-pyridylmethyl)ethylenediamine,bidentate ligand 2-(pyrazole-1-ylmethyl)pyridine,monodentate ligand 1-biphenyl-4-yl-1H-imidazole and transition metal Fe? ion.The effects of the steric hindrance in the paramagnetic Fe? building block on the transition temperature and light irradiation on the magnetic couplings between metal ions were both systematically investigated.In addation,the influence of host-guest interactions on the SCO behavior was also studied.(2)During the self-assembly of paramagnetic building block[Bu4N][pzTpFe?(CN)3]and transition metal Co? ion,two ID zigzag chains of 7 and 8 were designed and synthesized through introducing bridged ligand 1,4-bis-(1H-imidazol-l-yl)benzene and monodentate ligand l-biphenyl-4-yl-lH-imidazole,respectively.The charge transfer unit Fe?LS-CN-Co?Hs?Fe?LS-CN-C?LS with light response was introduced to the cyano-bridged lD chain structures.The influence of different lasers on metal-to-metal charge transfer behavior was also studied through 808 and 532 nm laser irradiation.The spin state,magnetic anisotropic and magnetic coupling channel between metal ions changed accompanied with MMCT,realizing the reversible control of generation and degeneration of bistable state in lD magnetic systems with laser.(3)During the self-assembly of paramagnetic building block[Bu4N][TpFe?(CN)3]and transition metal Co? ion,a linear centrosymmetric trinuclear compound of 9 was synthesized through introducing monodentate ligand 1-biphenyl-4-yl-lH-imidazole.The effect of temperature or light irradiation on charge transfer was studied in compound 9.The magnetization and polarization influenced by charge transfer behavior were further studied through theoretical and experimental methods;a ligand-bridged 2D layer of 10 was synthesized through introducing bridged ligand 1,4-bis-(lH-imidazol-1-yl)benzene.The control of magnetization and polarization induced by charge transfer and building blocks rotation was studied.