Effect of the chemical structure of a tetradentate equatorial ligand on the spin-crossover properties of the Fe (III) complexes chain structures: Electron paramagnetic resonance study

Abstract

The effect of the chemical structure of the equatorial ligand on the spin state of the Fe (III) ion in a series of 1-D chain complexes of the general formula [Fe(L)(tvp)]BPh₄ ·nCH₃ OH, where L = dianions of Schiff base containing a different number of aromatic groups: N,N'-ethylenebis (salicylaldimine) (salen) 1, N,N'-ethylenebis (acetylacetone)2,2'-imine (acen) 2, N,N'-ethylenebis (benzoylacetylacetone)2,2'-imine (bzacen) 3, and tvp = 1,2-di(4-pyridyl)ethylene, was studied by ultraviolet-visible (UV-vis) and electron paramagnetic resonance (EPR) methods. The values of exchange interactions, thermodynamic parameters of spin-crossover, and electronic structure features of the Fe (III) complexes were estimated from the EPR data. The substitution of a fragment of the equatorial ligand L in the series salen-acen-bzacen changes the local symmetry of the complex in the 1-D chain, thereby affecting the spin variable properties.

Keywords: EPR spectroscopy; Schiff base ligand; iron (III) complexes; spin crossover transition.