Molecular structure of complex [MnIIIMnIV(O)2(phen)4]3+ (phen = 1,10-phenanthroline) (a) and simplified model system (b), optimized at the broken symmetry unrestricted B3LYP level with the following basis set: LACVP for manganese, 6−31G(d) for oxo-bridge oxygen atoms, 6−31G for water oxygen atoms and N, 3−21G for carbon and hydrogen [14].