Geometric control of redox level in tetranuclear manganese and cobalt systems

A tetranucleating macrocyclic ligand derived from [2+2] Schiff-base condensation of 2,6-diformyl-4-methylphenol and 1,5-diaminopentan-3-ol was used to prepare a series of localised mixed-valence cobalt and manganese complexes. X-ray crystallographic structure analyses of one Co(II)4 complex, two Mn(II)2Mn(III)2 and two Co(II)Co(III)3 complexes are presented. The observed redox levels are accounted for in terms of geometric constraints transmitted from one metal ion to the next through the ligand framework, providing a basis for cooperative control of redox processes.