Macrocyclic effects upon isomeric CuIIMII and MIICuII cores. Formation with unsymmetric phenol-based macrocyclic ligands

This paper discusses coordination-position isomeric MIICuII and CuIIMII complexes, using unsymmetric dinucleating macrocycles (Lm;n)2– ((L2;2)2–, (L2;3)2– and (L2;4)2–) that comprise two 2-(N-methyl)-aminomethyl-6-iminomethyl-4-bromophenonate entities, combined through the ethylene chain (m = 2) between the two amine nitrogens and through the ethylene, trimethylene or tetramethylene chain (n = 2, 3 or 4) between the two imine nitrogens. The macrocycles have dissimilar N(amine)2O2 and N(imine)2O2 metal-binding sites sharing the phenolic oxygens. The reaction of the mononuclear CuII precursors, [Cu(L2;2)], [Cu(L2;2)] and [Cu(L2;2)], with a MII perchlorate and a MII acetate salt formed (acetato)MIICuII complexes: [CoCu(L2;2)(AcO)]ClO405H2O] (1), [NiCu(L2;2) (AcO)]ClO4 (2), [ZnCu(L2;2) (AcO)]ClO4 (3), [CoCu(L2;3)(AcO)]ClO405H2O (4), [NiCu(L2;3)(AcO)]ClO4 (5), [ZnCu(L2;3)(AcO)]ClO405H2O (6), [CoCu(L2;4)(AcO)(DMF)]ClO4 (7), [NiCu(L2;4) (AcO)]ClO42DMF (8) and [ZnCu(L2;4)(AcO)]ClO4 (9) (the formulation [MaMb (Lm;n)]2+ means that Ma resides in the aminic site and Mb in the iminic site). The site selectivity of the metal ions is demonstrated by X-ray crystallographic studies for 2MeOH,3, 5, 7, and 9. An (acetato)CuIIZnII complex, [CuZn(L2;3)(AcO)]ClO4 (10), was obtained by the reaction of [PbCu(L2;3)]-(ClO4)2 with ZnSO44H2O, in the presence of sodium acetate. Other complexes of the CuIIMII type were thermodynamically unstable to cause a scrambling of metal ions. The Cu migration from the iminic site to the aminic site in the synthesis of 10 is explained by the ‘kinetic macrocyclic effect’. The coordination-position isomers, 6 and 10, are differentiated by physicochemical properties.