ONE-EQUIVALENT OXIDATIVE CHARGE STORAGE ON AN [MN2O2](3- SYNTHESIS, CRYSTAL-STRUCTURE AND RESONANCE RAMAN-SPECTRA OF [MN2O2(PBZ)(4)](N+) (N=3, 4)() CORE )

Complexes similar in structure but with a higher oxidation state of th e metal center mimic charge-storage processes observed in biological s ystems. An oxomanganese system based on the ligand 2(2'-pyridyl)benzim idazole, [Mn2O2(pbz)(4)](3+), which contains the biologically relevant mixed-valent di-mu-oxo Mn(III,IV) unit capable of undergoing a pH con trolled one-electron redox conversion to the Mn(IV,IV) state, is descr ibed. The [Mn2O2(pbz)(4)](4+) and [Mn2O2(pbz)(4)](3+) complexes have b oth been isolated and structurally characterized by X-ray crystallogra phy and UV-Vis, EPR and resonance Raman spectroscopic methods. A chara cteristic Mn(IV)-O stretching mode of the (di-mu-oxo)dimanganese core in these complexes at similar to 695 cm(-1) provides a useful referenc e probe for structural characterization of Mn containing active sites involving two oxo bridges.