DICOPPER(II) COMPLEXES WITH HEXAAZA BINUCLEATING LIGANDS DERIVED FROMISOPHTHALDEHYDE AND DI(2-PYRIDYL) METHYLAMINE

New N-6 ligands derived from isophthaldehyde and di(2-pyridyl) methyla mine were synthesized, in order to probe the corresponding copper comp lexes as model systems of tyrosinase. Copper(II) complexes of the N-6 ligands: lpha,alpha'-bis(di(2-pyridyl)methylimino)-m-xylene (m-xylN(DP M)(2)) and lpha,alpha'-bis(di(2-pyridyl)methylamino)-m-xylene (m-xylNH (DPM)(2)) were obtained. [Cu-2(m-xylN(DPM)(2)(OCH3)(2)ClO4]ClO4 (1) an d [Cu-2(m-xylN(DPM)(2))(OH)(2)ClO4]ClO4 (2) were isolated by the oxida tion reaction of the cuprous species with molecular oxygen in methanol and dichloromethane solutions, respectively. Neither of the two dicop per(II) complexes showed insertion of oxygen at the arene ring under t he used experimental conditions. [Cu-2(m-xylNH(DPM)(2)Cl-4]. 2H(2)O (3 ) was synthesized by the direct reaction of the reduced organic ligand with cupric chloride. X-ray structures are reported: [Cu-2(m-xylN(DPM )(2)(OCH3)(2)ClO4]ClO4 (1), monoclinic P2(1)/n, a = 15.099(4), b = 11. 974(4), c = 19.928(5) Angstrom, beta = 93.95(1)degrees, Z = 4, R = 0.0 49; [Cu-2(m-xlN(DPM)(2))(OH)(2)ClO4]ClO4 (2), orthorhombic P2(1)2(1)2( 1), a = 14.188(4), b = 14.275(3), c = 16.763(4) Angstrom, Z = 4, R = 0 .062; [Cu-2(m-xylNH(DPM)(2)Cl-4]. 2H(2)O (3), monoclinic P2(1)/c, a = 13.353, b = 17.030(2), c = 15.547(2) Angstrom, beta = 112.38(1)degrees , Z = 4, R = 0.043; The coordination geometries of the Cu(II) ion in 1 and 2 are best described as tetragonally distorted octahedral, while in 3 it is trigonal bipyramidal. Compounds 1 and 2 are doubly bridged by methoxo and hydroxo groups; the bridging angles for 1 are Cu(1)-O(1 )-Cu(2) = 100.0(2)degrees and Cu(1)-O(2)-Cu(2) = 99.0(1)degrees, and f or 2 Cu(2)-O(1)-Cu(1) = 98.2(4) and Cu(2)-O(1)-Cu(l) = 96.4(4)degrees. The methoxo complex 1 is antiferromagnetic (T-M = 338 K) while the hy droxo complex 2 and the dicopper(II) complex 3 are paramagnetic.