Macrocyclic effects upon isomeric Cu(II)M(II) and M(II)Cu(II) cores. Formation with unsymmetric phenol-based macrocyclic ligands

This paper discusses coordination-position isomeric (MCuII)-Cu-II and (CuMI I)-M-II complexes, using unsymmetric dinucleating macrocycles (L-m;n)(2-) ( (L-2:2)(2-), (L-2:3)(2-) and (L-2;4)(2-)) that comprise two 2-(N-methyl)-am inomethyl-6-iminomethyl-4-bromophenonate entities, combined through the eth ylene chain (m = 2) between the two amine nitrogens and through the ethylen e, trimethylene or tetramethylene chain (n = 2, 3 or 4) between the two imi ne nitrogens. The macrocycles have dissimilar N(amine)(2)O-2 and N(imine)(2 )O-2 metal-binding sites sharing the phenolic oxygens. The reaction of the mononuclear Cn(II) precursors, [Cu(L-2:2)], [Cu(L-2:2)] and [Cu(L-2;2)], wi th a M-II perchlorate and a M-II acetate salt formed (acetato)(MCuII)-Cu-II complexes: [CoCU(L-2;2)(AcO)]ClO4. O . 5H(2)O] (1), [NiCu(L-2:2) (AcO)]ClO 4 (2), [ZnCu(L-2:2) (AcO)]ClO4 (3), [CoCu(L-2;3)(AcO)]ClO4. O . 5H(2)O (4), [NiCu(L-2:3)(AcO)]ClO4 (5), [ZnCu(L-2;3)(AcO)]ClO4. O . 5H(2)O (6), [CoCu( L-2;4)(AcO)(DMF)]ClO4 (7), [NiCu(L-2;4) (AcO)]ClO4. 2DMF (8) and [ZnCu(L-2; 4)(AcO)]ClO4 (9) (the formulation [MaMb (L-m;n)](2+) means that M-a resides in the aminic site and M-b in the iminic site). The site selectivity of th e metal ions is demonstrated by X-ray crystallographic studies for 2 . MeOH , 3, 5, 7, and 9. An (acetato)(CuZnII)-Zn-II complex, [CuZn(L-2:3)(AcO)]ClO 4 (10), was obtained by the reaction of [PbCu(L-2:3)]-(ClO4)(2) with ZnSO4. 4H(2)O, in the presence of sodium acetate. Other complexes of the (CuMII)- M-II type were thermodynamically unstable to cause a scrambling of metal io ns. The Cu migration from the iminic site to the aminic site in the synthes is of 10 is explained by the 'kinetic macrocyclic effect'. The coordination -position isomers, 6 and 10, are differentiated by physicochemical properti es.