Water is a key factor to alter the structure and electrochemical properties of carboxylate-bridged dimanganese(II) complexes.

The synthesis and physical properties of dimanganese(II) compounds with varying numbers of water ligands housed in the four bulky carboxylate motifs, including the first complex with a parallelogram core {Mn2(μ-OH2)2(μ-O2CR)}(3+) unit, are described. The isolation of these complexes revealed how water could alter the structural and electrochemical properties of similar carboxylate-bridged dimanganese(II) cores that may occur in a variety of active sites of Mn-containing metalloenzymes. These studies support the notion that water molecules in coordination spheres of active sites of metalloproteins are not a simple spectator medium but the modulation factor of structures and functions.