Structures and Magnetic Properties of Some Fe(III) Complexes with Hexadentate Ligands: in Connection with Spin-Crossover Behavior

Abstract

Abstract Several iron(III) complexes with the different hexadentate Schiff-base ligands of N4O2 donor sets were synthesized; these are 1 : 2 condensation products of linear tetramines (3,3,3-, 3,2,3-, 2,3,2- or 2,2,2-tetramine) and salicylaldehyde, acetophenone or benzophenone derivatives. Their crystal structures, Mössbauer spectra, magnetic susceptibilities, electronic spectra and cyclic voltammetry of the complexes were examined. The X-ray structures of the single crystals of [Fe(3,2,3-sal2tet)]NO3 (1), [Fe(3,2,3-sal2tet)]BPh4 (2), [Fe(3,2,3-mpk2tet)]PF6 (3), [Fe(2,3,2-sal2tet)]ClO4 (4), [Fe(2,3,2-3MeO-sal2tet)]ClO4 (5), [Fe(2,3,2-mpk2tet)]ClO4 (6), [Fe(2,3,2-bpk2tet)]ClO4 (7), and [Fe(2,2,2-bpk2tet)]ClO4·EtOH (8) were determined. The moieties of the iron atoms of (1), (2), and (3) with 3,2,3-tetramine, and (7) with 2,3,2-tetramine were pseudo octahedral with trans-FeN4O2 geometry. Those of (4), (5), and (6) with 2,3,2-tetramine, and (8) with 2,2,2-tetramine were cis-FeN4O2 geometry. The iron(III) complexes (1), (2), (3), and (7) were in the low-spin state, and the iron(III) complexes (4), (5), (6), and (8) were in the high-spin state. In the electronic spectra, the wave lengths of the LMCT bands for the low-spin complexes were longer than those for the high-spin complexes. The values of redox potentials for the low-spin states were suggested to be 0.12 V more negative than those for the high-spin states. (Remark: This summary is partially truncated in the html because it exceeds the limit of the system (4000 characters per note). The complete text is given in the pdf.)