Abstract

New N 6 ligands derived from isophthaldehyde and di(2-pyridyl)methylamine were synthesized, in order to probe the corresponding copper complexes as model systems of tyrosinase. Copper(II) complexes of the N 6 ligands: ?,??-bis(di(2-pyridyl)methylimino)-m-xylene (m-xylN(DPM) 2) and ?,??-bis(di(2-pyridyl)methylamino)-m-xylene (m-xylNH(DPM) 2) were obtained. [Cu 2(m-xylN-(DPM) 2(OCH 3) 2ClO 4]ClO 4 (1) and [Cu 2(m-xylN(DPM) 2) (OH) 2ClO 4]ClO 4 (2) were isolated by the oxidation reaction of the cuprous species with molecular oxygen in methanol and dichloromethane solutions, respectively. Neither of the two dicopper(II) complexes showed insertion of oxygen at the arene ring under the used experimental conditions. [Cu 2(m-xylNH(DPM) 2Cl 4] · 2H 2O (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(OCH 3) 2ClO 4]ClO 4 (1), monoclinic P2 1/n, a = 15.099(4), b = 11.974(4), c = 19.928(5) Å, ? = 93.95(1)°, Z=4, R = 0.049; [Cu 2(m-xylN(DPM) 2)(OH) 2ClO 4]ClO 4 (2), orthorhombic P2 12 12 1, a = 14.188(4), b = 14.275(3), c = 16.763(4) Å, Z = 4, R = 0.062; [Cu 2(m-xylNH(DPM) 2Cl 4] · 2H 2O (3), monoclinic P2 1/c, a = 13.353, b = 17.030(2), c = 15.547(2) Å, ? = 112.38(1)°, 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)° and Cu(1)-O(2)-Cu(2) = 99.0(1)°, and for 2 Cu(2)-O(1)-Cu(1) = 98.2(4) and Cu(2)-O(1)-Cu(1) = 96.4(4)°. The methoxo complex 1 is antiferromagnetic ( T M = 338 K) while the hydroxo complex 2 and the dicopper(II) complex 3 are paramagnetic.