Spin Crossover and Thermochromism in Iron(II) Complexes with 2,6-Bis(1 H -imidazol-2-yl)-4-methoxypyridine.

New iron(II) complexes with 2,6-bis(1 H -imidazol-2-yl)-4-methoxypyridine ( L ) of the composition [FeL 2 ]A n ∙mH 2 O (A = SO 4 2- , n = 1, m = 2 ( I ); A = ReO 4 - , n = 2, m = 1 ( II ); A = Br - , n = 2, m = 2 ( III )) have been synthesized and investigated. To determine the coordination ability of the ligand, a single crystal of a copper(II) complex of the composition [CuLCl 2 ] ( IV ) was obtained and studied by X-ray technique. Compounds I - III were studied using methods of X-ray phase analysis, electron (diffuse reflection spectra), infrared and Mössbauer spectroscopy, static magnetic susceptibility. The study of the µ eff (T) dependence showed that the 1 A 1 ↔ 5 T 2 spin crossover manifests itself in the compounds. The spin crossover is accompanied by thermochromism: there is a distinct color change orange ↔ red-violet.