High-Temperature Spin Crossover in Ironpyridine

Novel iron(II) coordination compounds containing a ligand 2,6-bis(1H-imidazol-2-yl)pyridine (L), having such a composition as [FeL[sub.2]]SO[sub.4]·0.5H[sub.2]O, [FeL[sub.2]]Br[sub.2]·H[sub.2]O, [FeL[sub.2]](ReO[sub.4])[sub.2], [FeL[sub.2]]B[sub.10]H[sub.10]∙H[sub.2]O, [FeL[sub.2]]B[sub.12]H[sub.12]∙1.5H[sub.2]O had been synthesized and studied using UV-Vis (diffuse reflectance), infrared, extended X-ray absorption fine structure (EXAFS), and Mössbauer spectroscopy methods, as well as X-ray diffraction and static magnetic susceptibility methods. The analysis of the μ[sub.eff](T) dependence in the temperature range of 80-600 K have shown that all the obtained complexes exhibit a high-temperature spin crossover [sup.1]A[sub.1] ↔ [sup.5]T[sub.2].