Reactions of 1,10-phenanthroline-2,9-dicarboxylic acid (H2phenda) with MnCl2·4H2O or MCl2·6H2O (M = Co, Ni) under solvothermal conditions yielded three octahedral clusters, (H3O)[MnII6(μ6-Cl)(phenda)6]·8MeOH (1·8MeOH), (H3O)[MII6(μ6-Cl)(phenda)6]·6H2O (M = Co, 2·6H2O; M = Ni, 3·6H2O). In the title compounds, the six metal centers are bridged by a μ6-Cl− and surrounded by six H2phenda ligands, forming an octahedral cluster. Magnetic studies show that the antiferromagnetic interactions are present in 1·8MeOH, 2·6H2O and 3·6H2O. Moreover, 3·6H2O clearly shows a nonzero out-of-phase χ″ signal with a peak at ca. 11 K, accompanied by a broad one for χ′.