CONSEQUENCES OF ELECTRONIC STERIC EFFECTS ON MONOCHELATE AND BISCHELATE MANGANESE(II) (S=5/2) COMPLEXES USING PYRIDINYLPYRAZOLE LIGANDS - SYNTHESIS AND ELECTROCHEMISTRY

A group of three high-spin manganese(II) bis-chelates were synthesized using tridentate 2,6-bis(pyrazol-1-ylmethyl)pyridine and its methyl substituted derivatives. The complexes were isolated as crystalline diperchlorate salts. Two five-coordinate mono-chelates with two chlorides as co-ligands were also synthesized. All the complexes were characterized using conventional physico-chemical techniques. Nucleophilic halide displacement reactions in water on the dichloro complexes afforded aqua complexes. When examined by cyclic voltammetry each complex displays an irreversible Mn(III)/Mn(II) couple. The trends in the anodic peak potentials are rationalized on the basis of electronic/steric effects of the methyl groups present near the donor site.