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

Abstract

New iron(II) complexes with 2,6-bis(1H-imidazol-2-yl)-4-methoxypyridine (L) of the composition [FeL₂]A_n∙mH₂O (A = SO₄^2-, n = 1, m = 2 (I); A = ReO₄^-, 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 [CuLCl₂] (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 ¹A₁ ↔ ⁵T₂ spin crossover manifests itself in the compounds. The spin crossover is accompanied by thermochromism: there is a distinct color change orange ↔ red-violet.

Keywords: 2,6-bis(1H-imidazol-2-yl)-4-methoxypyridine; complexes; iron(II); spectroscopy; spin crossover; synthesis.