A Mononuclear Iron(II) Spin-Crossover Molecule Decorated by Photochromic Azobenzene Group.

Aiming at constructing photoresponsive spin crossover (SCO) behavior, herein we designed a new ligand Abtz (Abtz = ()--(4-(()-phenyldiazenyl)phenyl)-1-(thiazol-4-yl)methanimine) which was decorated by a photochromic azobenzene group. Based on this photochromic ligand, a mononuclear Fe(II) SCO molecule [Fe(Abtz)](BF)·(EAC) (, EAC = ethyl acetate) was successfully synthesized and showed a complete one-step SCO behavior. Under continuous UV light and blue-light exposure, the photoisomerization of both ligand Abtz and compound in the liquid phase was confirmed through UV-Vis spectra. Moreover, the H-NMR spectra of Abtz reveal a conversion ratio of 37%. Although the UV-Vis spectra reveal the photochromic behavior for in the solution phase, the SCO behavior in the liquid state is absent according to the variable-temperature Evans method, suggesting the possible decomposition. Moreover, in the solid state, the photoisomerization of both Abtz and was not observed, due to the steric hindrance.