A Mössbauer spectroscopic study of the electronic states of tetragonal iron(II) pyridine complexes

Abstract

The Mössbauer spectra of FeL 4Cl 2 (L = pyridine, 4-methylpyridine, 3-acetylpyridine) and Fe L 2Cl 2 (L = pyridine, 4-acetylpyridine, 4-chloropyridine, 3-chloropyridine) were measured between 4·2 and 290°K. The magnitudes of the quadrupole splittings ( ΔE Q ) of FeL 4Cl 2 are much larger than those of FeL 2Cl 2, probably because of the different orbital ground-states: d xy for FeL 4Cl 2 and, most likely, d xz and d yz for FeL 2Cl 2. The energy separation, δt 2 g , was estimated from the temperature dependence of ΔE Q . No effect on the isomer shift of a substituent at the 3- or 4-position of pyridine is observed in either FeL 4Cl 2 or FeL 2Cl 2.