Design And Construction Of Synergic Spin Crossover And Fluorescence Complexes

Spin crossover-fluorescence bifunctional molecular materials are actively sought in the fields of chemistry and material,due to the wide application prospect in molecular switches and thermometry.Herein,a series of new molecular system combining spin crossover(SCO)and fluorescence were designed and synthesized to reveal synergetic effects between spin crossover and fluorescence.The main research results are as follows:(1)Spin crossover complexes 1 and 2 were synthesized based on the chelating ligands pyrazino[2,3-f][1,10]phenanthroline and dipyrido[3,2-a:2',3'-c]-(6,7,8,9-tetrahydro)phenazine.Both 1 and 2 exhibited thermal-induced SCO behaviour above room temperature.In particular,2 exhibited a 30 K wide hysteresis loop with T1/24?=341 K and T1/2T=371 K.Three binuclear Fe? complexes 3-5 were synthesized based on the bridging ligands triphenylamine-1-yl-N-(4H-1,2,4-triazol-4-yl)methanimine and naphthyl-N-(4H-1,2,4-triazol-4-yl)methanimine,wherein 3 showed antiferromagnetism and complexes 4 and 5 exhibited a reversible light-induced SCO behavior by alternating irradiation under 532 nm and 808 nm laser.(2)Six SCO complexes 6-11 and one high spin(HS)complex 12 were synthesized by the reaction of fluorescent ligands with different ? electron conjugation and Fe? ions in the presence of co-ligands NCS-,NCSe-,N(CN)2-,and Cl-,wherein complexes 6-10 showed the light induced spin crossover.The temperature dependent fluorescence emission spectra indicated that the fluorescence intensity of complexes 6,7,9,and 10 all monotonically increased on cooling and was not affected by the Fe? spin states,indicating the coexistence of fluorescence and spin crossover.(3)Four thermal and light-induced SCO complexes 13-16 were assembled with Fe? ions and(triphenylamine-1-yl)-N-(3,5-bi(pyridin-2-yl)-4H-1,2,4-triazol-4-yl)methanimine,and(pyrene-1-yl)-N-(3,5-bi(pyridin-2-yl)-4H-1,2,4-triazol-4-yl)methanimine,respectively.Fluorescence emission of 13,14,and 16 all showed a strong dependence on Fe? spin state near the spin transition temperature,indicative of the synergy between spin crossover and fluorescence.Magnetic and fluorescent properties after irradiation suggested that a synergetic SCO-fluorescence effect was present.To our best knowledge,this is the first example of bifunctional SCO-fluorescence compound shows the synergy between light-induced spin crossover and fluorescent property.