Unsymmetrically ligated dioxobridged Mn(III, IV) complexes—synthesis and spectral studies

Abstract

The mixed valence Mn(III, IV) complexes, [Mn2O2L4]X3 with L=2,2-bipyridine or 1,10-phenanthroline and X=ClO 4 − or PF 6 − undergo partial ligand displacement reactions giving rise to the new compounds [Mn2O2L3A2]X3 with A=N, N-dimethylformamide or pyridine. The substitution is believed to take place at the labiled 4, Mn(III) centre. The substituted complexes have more deeply trapped valencies based on their electronic spectral characteristics. The EPR spectra are found to be essentially unaffected by ligand substitutions. Computer simulations of frozen solutions as well as polycrystalline spectra of the PF 6 − salts showing hyperfine splittings are presented. All the complexes evolve oxygen from water when present as a solid phase in contact with an aqueous solution containing Ce4+ions. The oxygen-evolving solution is found to contain MnO 4 − ions.