Spin crossover in iron(II) complexes with new ligand 2,6-bis(4,5-dimethyl-1H-imidazole-2-yl)pyridine

Abstract

Iron(II) coordination compounds containing a new ligand, 2,6-bis(4,5-dimethyl-1H-imidazol-2-yl)pyridine (L), of composition [FeL2](NO3)2·H2O (1·H2O), [FeL2](ClO4)2·0.5H2O (2·0.5H2O), [FeL2]SO4·0.5H2O (3·0.5H2O), or [FeL2](ReO4)2·2H2O (4·2H2O) have been synthesized and studied by UV–vis (diffuse reflectance), infrared, extended X-ray absorption fine structure (EXAFS), and Mössbauer spectroscopies, as well as X-ray diffraction and static magnetic susceptibility methods. The structure of a copper(II) complex with L of composition [CuL2]SO4·3H2O has been successfully determined. The analysis of the μeff(T) dependence in the temperature range of 80–520 K showed that complexes [FeL2](NO3)2·H2O, [FeL2](ClO4)2·0.5H2O, and [FeL2](ReO4)2·2H2O and their dehydrated counterparts are subject to high-temperature spin crossover 1A1 ↔ 5T2.