Experimental and Theoretical Identification of the Origin of Magnetic Anisotropy in Intermediate Spin Iron(III) Complexes

Abstract

The complexes [FeL^N2S2 X] [in which L^N2S2 =2,2'-(2,2'-bipryridine-6,6'-diyl)bis(1,1'-diphenylethanethiolate) and X=Cl, Br and I], characterized crystallographically earlier and here (Fe(L)Br), reveal a square pyramidal coordinated Fe^III ion. Unusually, all three complexes have intermediate spin ground states. Susceptibility measurements, powder cw X- and Q-band EPR spectra, and zero-field powder Mössbauer spectra show that all complexes display distinct magnetic anisotropy, which has been rationalized by DFT calculations.