Spin Exchange Coupling in Heterobimetallic MIIVIVO (M = Cu, Ni, Co, Fe, Mn) Macrocyclic Complexes. Synthesis, Structure, and Properties

A series of heterobimetallic complexes [(V IV O)L1Cu II (μ-OAC)(MeOH)](ClO 4 ) ( 1 ) and [(V IV O)L1M II (μ-OAc)(H 2 O)](ClO 4 )·H 2 O (M = Ni ( 2 ), Co ( 3 ), Fe ( 4 ), Mn ( 5 )) derived from a symmetric tetraaminodiphenol macrocyclic ligand H 2 L1 have been synthesized and characterized. The crystal structure of 1 has been determined. The complex (C 27 H 41 N 4 O 10 ClCuV) crystallizes in the monoclinic space group P 2 1 / c with a = 13.227(3) Å, b = 14.932(3) Å, c = 17.019(3) Å, β = 112.29(1)°, and Z = 4. Both the metal centers in 1 are six-coordinated and are triply bridged by the two phenolate and the acetate oxygens; the sixth coordination site of the copper atom is occupied by a distantly placed methanol oxygen (Cu−O = 2.452(5) Å), while that of the vanadium by the oxo oxygen (V−O = 1.627(4) Å). The metal centers are separated by 3.066(1) Å, and the dihedral angle (Δ) between the metal planes is 32.0°. Variable-temperature (4−300 K) magnetic susceptibility measurements of 1 − 5 and of [(V IV O)L2Cu II (μ-OAc)(H 2 O)](ClO 4 ) ( 6 ) (where H 2 L2 is an asymmetric tetraaminodiphenol macrocyclic ligand) have been made and treated with the spin-Hamiltonian H = −2 J S 1 · S 2 . All the complexes, except 5, exhibit ferromagnetic exchange interaction with the following values of J (in cm - 1 ): 42.5 ( 1 ), 12.0 ( 2 ), 4.4 ( 3 ), 4.4 ( 4 ), and 46.0 ( 6 ); complex 5 behaves antiferromagnetically with J = −14.2 cm - 1 . A linear correlation between J and Δ has been proposed for Cu II V IV O complexes.