SYNTHESIS AND CHARACTERIZATION OF DINUCLEAR COPPER(II) COMPLEXES OF THE DINUCLEATING LIGAND 2,6-BIS[(BIS((1-METHYLIMIDAZOL-2-YL)METHYL)AMINO)METHYL]-4-METHYLPHENOL

The synthesis, crystal structures, and magnetic and spectroscopic properties are reported for a series of dinuclear copper(II) complexes of the novel dinucleating polyimidazole ligand 2,6-bis[(bis((1-methylimidazol-2-yl)methyl)amino)methyl]-4-methylphenol (Hbimp). The copper complexes have both "open" ([Cu2(bimp)(H2O)2](ClO4)3 (2) and [Cu2(bimp)(CH3OH)2(ClO4)3 (3)) and "closed" ([Cu2(bimp)(OCH3)](ClO4)2 (4) and [Cu2(bimp)(N3)](ClO4)2 (5)) type structures. X-ray crystal structures of complexes 3 and 4 were determined with Mo K-alpha radiation. Crystal data: 3, C31H45N10Cu2Cl3O15, monoclinic, P2(1)/n, a = 17.855 (3) angstrom, b = 13.377 (3) angstrom, c = 18.054 (4) angstrom, beta = 105.78 (2)-degrees, Z = 4, R(F) = 0.051 for 5074 independent data [I greater-than-or-equal-to 3-sigma-(I)]; 4, C32H48N10Cu2Cl2O12, monoclinic, C2/c, a = 23.221 (3) angstrom, b = 12.903 (2) angstrom, c = 17.681 (3) angstrom, beta = 125.34 (1)-degrees, Z = 4, R(F) = 0.054 for 2439 independent data [I greater-than-or-equal-to 3-sigma-(I)]. In complex 3, the copper ions are pentacoordinate, bonded to two imidazoles, a tertiary amine nitrogen, a methanol oxygen atom, and the bridging phenolate oxygen atom. The dinuclear complex has a Cu(1)-O(1)-Cu(2) angle of 142.9 (2)-degrees and a Cu-Cu separation of 4.090 (1) angstrom. In complex 4, the copper ions also are pentacoordinate, bridged both by the phenolate oxygen atom and by a methoxide ion. The Cu-Cu' separation is 3.026(1) angstrom with a Cu-O(1)-Cu' angle of 98.7 (1)-degree. Magnetic susceptibility measurements reveal that there is no appreciable exchange interaction between the copper ions in complexes 2 and 5 (\J\ less-than-or-equal-to 0.3 cm-1), over the temperature range 2-300 K. In complex 4, magnetic data indicate that the copper ions are involved in a moderate antiferromagnetic exchange interaction (J = -47 cm-1 over the temperature range 5-300 K. Differences in the strength of the magnetic exchange interactions are rationalized by using a magnetic orbital approach. UV-visible electronic spectral and EPR spectral data are presented for each complex.