Relation between electronic and spatial structure and spin-transition parameters in chain-like Fe(II) compounds

EXAFS spectroscopy is used to investigate the characteristic features of the spatial and electronic structure of the polynuclear iron(II) complexes with 1,2,4-triazoles and various anions. The spin transition has been found to be accompanied by drastic changes in spatial structure. The increase in spin transition temperature for the complexes with variable anions ClO super(-) sub(4), I super(-), Br super(-), BF super(-) sub(4), NO super(-) sub(3) was found to correlate with changes in the Fe-N distances and changes in bond covalence determined from the chemical shifts in Moessbauer spectra.