Synthesis And Tunable Magnetic Properties Of Molecular Magnets With Fe/Co Heterospin

Two parts in this work were included based on an idea of using tricyanide building blocks to prepare a single-chain magnet or single-molecular magnet. Firstly, a single-molecular magnet with large spin-state have been synthesized viaadjusting the propertions of the raw materials; secondly, a light-induced spin crossover actuated single chain magnet have been prepared by changing different ligands to adjust the ligand-field of metal ions, which provide an approach to control the behavior of SMM via LIESST effectsuccessfully.(1) Five cyanide-bridged polynuclear heterometalic compounds based on tricyanide building blocks [(Bu4N)Fe(Tp)(CN)3] and [(Bu4N)Fe(Tp*)(CN)3] (Tp= hydrotris(pyrazolyl)borate; Tp*= hydridotris(3.5-dimethylpyrazol-lyl)borate) have been traditionally prepared by introducing three ancillary ligands (tptz= 2,4,6-tri(2-pyridine)-1.3,5-triazine for compoundsland2;cyclen= tetraazacyclododecane for compound 3; bpp= 1,3-(2-pyridine) propane for compounds4and 5) and three metal ions (Fe? for 1 and 5, Co? for 2 and 4, Ni? for 3), and all of them have been characterized structurally and magnetically. Compounds 1,2 and 3 present ferromagnetic behavior, compound 4 present ferrimagnetic behavior. Notably.compound 5 has the largest molecular ground state spin of S= 45 known to date, which provided a new research direction to synthesis a multinuclear cluster with large spin-state by a rational "bottom-up" method.(2) Series of compounds with low-dimensional structure have been prepared by changing different ligands. Firstly, four comounds with 1D chain structure have been synthesized by choosing two multidentate ligands (cyclen for compounds6-8, tptz= 2,4,6-tri(2-pyridine)-1,3,5-triazine for compound9) to occupy multiple metal sites. They present antiferromagnetic and ferromagnetic behavior, respectively. Secondly, choosing 4.4'-phenylazopyridine (papy) as second ligand, four compounds (10-13) with double zigzag chain structure were obtained. They present metamagnetic. ferromagnetic and ferrimagnetic behavior, respectively. Lastly, changing the bridged ligand papy to 4.4'-azopyridine (azp). three compounds (14-16) with 2D layer structure were prepared. The analysis of magnetism indicates that compound 16 present metamagnetic and single-chain magnetic behavior.(3) Using 4.4'-phenylazopyridine (papy) and 4,4'-azopyridine (azp) to tune the ligand field, compounds17-19with ID zigzag chain and 2D layer network were synthesized. Both compounds 17 and 18 possess temperature induced spin-crossover behavior. When 19 was irradiated, it showed photoinduced spin transition, providing synergy between the LIESST effect at Fe? sites and the antiferromagnetic interaction between photoinduced HS Fe? and LS Fe? ions along the chain. Compound 20 was synthesized by choosing the ligand N,N'-Bis-pyridin-4-ylmethyene-hydrazin(bpmh) instead of papy and azp to increase the distance between the neighboring chains. In which, single-chain magnet behaviour was firstly actuated accompanying the synergy between light-induced excited spin-state trapping (LIESST) at the Fe? sites and ferromagnetic between the photoinduced high-spin Fe? and low-spin Fe? ions in the chain.