Consequences of electronic/steric effects on monochelate and bischelate manganese(II) (S =5/2 ) complexes using pyridinylpyrazole ligands. Synthesis and electrochemistry

Abstract

A group of three high-spin manganese(II) bis-chelates were synthesized using tridentate 2,6-bis(pyrazol-l-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.