Mn-III(bpy)Cl3H2O (Goodwin, H. A.; Sylva, R. N. Aust. J. Chern. 1965, 18, 1743) crystallizes in the triclinic space group P (1) over bar, with a = 6.627(1) Angstrom, b = 9.991(7) Angstrom, c = 10.116(4) Angstrom, alpha = 84.38(4)degrees, beta = 73.47(3)degrees, gamma = 78.48(3)degrees, V = 629 Angstrom,(3) and Z = 4. The Mn-III ion has an octahedral surrounding distorted by a strong Jahn-Teller effect. Two chloride ions and the water molecule an involved into a network of hydrogen bonds. a careful study of aqueous solutions of (MnLCl3H2O)-L-III (L = bipyridine or phenanthroline) at different PII demonstrated the formation by condensation and disproportionation of [(L2MnO2MnL2)-O-III-L-IV](ClO4)(3) (Cooper, S. R.; Calvin, M. J. Ain. Chern. Sec. 1977. 99, 6623), [(Mn3O4L4)-O-IV(H2O)(2)](ClO4)(4) (Sarneski, J. E.; et al. J. Am. Chem. Sec. 1990, 112, 7255) and [Mn4O6(bpy)(6)](ClO4)(4) (Philouze, C.; et al. J. Am. Chem. Soc. 1994, 116, 8557). Condensation of MnLCl3H2O has been studied theoretically using partial charge models. It was possible to identify the mononuclear Mn-III and Mn-IV species which are able to condense through oxolation into polynuclear Mn-IV or mixed-valence Mn-III-Mn-IV complexes. It is then shown that direct electron transfer between Mn-III species is either assisted by the solvent or associated with the transfer of a bpy ligand from Mn-II toward Mn-IV. Formation of chainlike tetramers is thermodynamically unfavorable and has to be assisted by the solvent to occur. The greater hydrophobicity of phenanthroline in comparison with bipyridine explains why the chainlike tetramer is not obtained in the case of phenanthroline. Substitution of an oxo bridge by two carboxylato bridges appears to be the key point for the stabilization of a chainlike tetramer similar to that proposed from EXAFS to exist in the plant oxygen evolving complex.