Coordination-Position Isomeric M^IICu^II and Cu^IIM^II (M = Co, Ni, Zn) Complexes Derived from Macrocyclic Compartmental Ligands

The dinucleating macrocyclic ligands (L2;2)2- and (L2;3)2-, comprised of two 2-[(N-methylamino)methyl]-6-(iminomethyl)-4-bromophenolate entities combined by the −(CH2)2− chain between the two aminic nitrogen atoms and by the −(CH2)2− or −(CH2)3− chain between the two iminic nitrogen atoms, have afforded the following MIICuII complexes: [CoCu(L2;2)](ClO4)2·MeCN (1A), [NiCu(L2;2)](ClO4)2 (2A), [ZnCu(L2;2)](ClO4)2·0.5MeCN·EtOH (3A), [CoCu(L2;3)(MeCN)(2-PrOH)](ClO4)2 (4A), [NiCu(L2;3)](ClO4)2 (5A), and [ZnCu(L2;3)](ClO4)2·1.5DMF (6A). [CoCu(L2;2)(MeCN)3](ClO4)2 (1A‘) crystallizes in the monoclinic space group P21/n, a = 11.691(2) Å, b = 18.572(3) Å, c = 17.058(3) Å, β = 91.18(2)°, V = 3703(1) Å3, and Z = 4. [NiCu(L2;2)(DMF)2](ClO4)2 (2A‘) crystallizes in the triclinic space group P1̄, a = 11.260(2) Å, b = 16.359(6) Å, c = 10.853(4) Å, α = 96.98(3)°, β = 91.18(2)°, γ = 75.20(2)°, V = 1917(1) Å3, and Z = 2. 4A crystallizes in the monoclinic space group P21/c, a = 15.064(8) Å, b = 11.434(5) Å, c = 21.352(5) Å, β = 95.83(2)°, V = 3659(2) Å3, and Z = 4. The X-ray crystallographic results demonstrate the MII to reside in the N(amine)2O2 site and the CuII in the N(imine)2O2 site. The complexes 1−6 are regarded to be isomeric with [CuCo(L2;2))](ClO4)2·DMF (1B), [CuNi(L2;2))](ClO4)2·DMF·MeOH (2B), [CuZn(L2;2))](ClO4)2·H2O (3B)), [CuCo(L2;3))](ClO4)2·2H2O (4B), [CuNi(L2;3))](ClO4)2 (5B), and [CuZn(L2;3))](ClO4)2·H2O (6B) reported previously, when we ignore exogenous donating and solvating molecules. The isomeric MIICuII and CuIIMII complexes are differentiated by X-ray structural, magnetic, visible spectroscopic, and electrochemical studies. The two isomeric forms are significantly stabilized by the “macrocyclic effect” of the ligands, but 1A is converted into 1B on an electrode, and 2A is converted into 2B at elevated temperature.