DINUCLEAR COPPER(II) AND MIXED-VALENCE COPPER(II) COPPER(I) COMPLEXES OF 34-MEMBERED MACROCYCLIC LIGANDS (H2M1, H2M2) CAPABLE OF FORMING ENDOGENOUS PHENOLATE AND PYRIDAZINO BRIDGES - X-RAY CRYSTAL-STRUCTURES OF THE DINUCLEAR COPPER(II) COMPLEXES [CU2M1][BF4]2.H2O AND [CU2M2][BF4]2.CH3OH, WHICH EXHIBIT A REMARKABLE LIGAND TWIST

The synthesis, spectroscopic, magnetic, and electrochemical properties of a series of dinuclear copper(II) and mixed-valence copper(II)-copper(I) complexes with the 34-membered macrocyclic ligands H2M1 and H2M2 are described. The complexes [Cu2(L)]X2 (L = MI, X = BF4 (I), ClO4 (II); L = M2, X = BF4 (III), ClO4 (IV)) are formed by the template condensation of 2,6-diformyl-4-(R)-phenol (2 equiv) (R = CH3, MI; R = tBu, M2) with 3,6-bis-((aminoethyl)thio)pyridazine (2 equiv) in the presence of copper(II) salt. The single crystal X-ray structures of [CU2(Ml)](BF4)2.H2O(I) and [CU2(M2)](BF4)2.CH,OH(III) have been determined. I crystallized in the monoclinic system, space group C2/c with a = 38.80 (2) angstrom, b = 12.618 (6) angstrom, c = 18.366 (8) angstrom, beta = 112.42 (4)-degrees, and Z = 4. Refinement by full-matrix least-squares techniques gave final residuals R = 0.081 and R(w) = 0.058. III recrystallized in the triclinic system, space group P1BAR with a = 14.194 (3) angstrom, b = 15.887 (3) angstrom, c = 12.240 (3) angstrom, alpha = 107.54 (2)-degrees, beta = 1 13.22 (2)-degrees, gamma = 82.44 (2)-degrees, and Z 2. Refinement by full-matrix least-squares techniques gave final residuals R = 0.059 and R(w) = 0.050. A macrocyclic ligand twist (approximately 150-degrees) leads to significant distortion at the phenoxide-bridged dicopper centers and brings the pyridazine rings into a position for weak axial contact. Variable-temperature magnetic measurements indicate strong antiferromagnetic coupling (-2J = 560-750 cm-1) for I-IV. Two quasireversible one-electron redox steps are observed (cyclic voltammetry) at -0.08 to -0.1 V and -0.64 to -0.67 V (vs SCE), corresponding to the formation of Cu(II)-Cu(I) and Cu(I)-Cu(I) species, respectively. A series of mixed-valence(Cu(II)-Cu(I)) species has been generated by controlled potential electrolysis of I-IV and characterized by EPR spectroscopy.