New supramolecular complexes of manganese(II) and cobalt(II) with nucleic bases. Crystal structures of [M(H2O)6(1-Mecyt)6][ClO4]2·H2O, [Co(1-Mecyt)4][ClO4]2 and [M(H2O)4(cyt)2][ClO4]2·2cyt·2H2O [M = CoII or MnII; cyt = cytosine; 1-Mecyt = 1-methylcytosine]