Synthesis, Spectroscopy and Magnetic Characterization of Five Dinuclear Copper(II) Complexes with 2, 3 or 4-Pyridinemethanol as the Ligand

The synthesis, spectroscopy and magnetic characterization of five new dinuclear copper(II) complexes are described. All five compounds have the general formula [Cu2(L)4(O-R)2](Cl)2 or [Cu2(L)2(Cl)2](Cl)2, in which R = CH3 or H, L=2, 3 or 4-pyridinemethanol as L2, L3 or L4, respectively. The title compounds consist of dinuclear units with bridging methoxo groups in [Cu2(L4)4(O-CH3)2](Cl)2, hydroxo groups in [Cu2(L4)4(OH)2](Cl)2, and bridging chloro moeities in [Cu2(L4)4(Cl)2](Cl)2, [Cu2(L3)4(Cl)2](Cl)2 and [Cu2(L2)4(Cl)2] (Cl)2. Each dinuclear unit consisting of two ligands linked to each copper via the pyridine N atom, providing a Cu2N2A2 unit (where A = OH, O-CH3 or Cl). All complexes have been synthesized in a one-step reaction and characterized by elemental analysis, Fourier transform infrared (FTIR), electron spin resonance (ESR), and electronic spectra and by room temperature magnetic moments. The compounds exhibit antiferromagnetic interaction at room temperature. The UV-Vis spectra show three absorptions attributed to the d-d transition of the copper (II) ion, ligand?metal charge transfer and ???* or n??* transitions of the ligand. The FTIR spectra indicate a Cu2N2A2 ring vibrating from 395 to 530 cm-1. All complexes show a room temperature magnetic moment between 1.55 and 1.67 B.M. per copper atom. The X-band electron spin resonance (ESR) spectra of samples in DMF or DMSO frozen at liquid nitrogen temperature show a typical ?m = 1 transition.