Binuclear copper(II) oxidation products from copper(I) complexes with tridentate ligands.: Magnetostructural characterization

The bis-pyridine tridentate ligands (6-R-2-pyridylmethyl)-(2-pyridylmethyl) benzylamine (RDPMA, where R = CH3, CF3) (6-R-2-pyridylmethyl)-(2-pyridylethyl) benzylamine (RPMPEA, where R = CH3, CF3) and the bidentate ligand di-benzyl-(6-methyl-2-pyridylmethyl)amine (BiBzMePMA) have been synthesized and their copper(I) complexes oxidized in a methanol solution to afford self-assembled bis-gamma-methoxo-binuclear copper(II) complexes (1, 2, 4, 6) or hydroxo- binuclear copper(II) complexes (3). Oxidation of the nonsubstituted DPMA (R = H) in dichloromethane gives a chloride-bridged complex (5). The crystal structures for [Cu(MeDPMA)(MeO)](2)(ClO4)(2) (1), [Cu(RPMPEA)(MeO)(12)(ClO4)(2) (for 2, R= Me, and for 4, R = CF3), [Cu(BiBzMePMA)(MeO)](2)(ClO4)(2) (6), [Cu(FDPMA)(OH)](2)(ClO4)(2) (3), and [Cu(DPMA)(Cl)(12)(ClO4)(2) (5) have been determined, and their variable-temperature magnetic susceptibility has been measured in the temperature range of 10-300 K. The copper coordination geometries are best described as square pyramidal, except for 6, which is square planar, because of the lack of one pyridine ring in the bidentate ligand. In 1-4 and 6, the basal plane is formed by two pyridine N atoms and two O atoms from the bridging methoxo or hydroxo groups, whereas in 5, the bridging Cl atoms occupy axial-equatorial sites, Magnetic susceptibility measurements show that the Cu atoms are strongly coupled antiferromagnetically in the bis-methoxo complexes 1, 2, 4, and 6, with -2J > 600 cm(-1), whereas for the hydroxo complex 3, -2J = 195 cm(-1) and the chloride-bridged complex 5 shows a weak ferromagnetic coupling, with 2J = 21 cm(-1) (2J is an indicator of the magnetic interaction between the Cu centers).