SYNTHESIS, CRYSTAL-STRUCTURE AND MAGNETIC-PROPERTIES OF A LINEAR TRINUCLEAR COPPER(II) COMPOUND WITH CHLORIDE AND 4-AMINO-3,5-BIS(HYDROXYMETHYL)-1,2,4-TRIAZOLE AS BRIDGING LIGANDS

A new linear trinuclear copper(II) co-ordination compound of the formula [Cu3(H2ahmt)6Cl4]Cl2, where H-2ahmt = 4-amino-3,5-bis(hydroxymethyl)-1,2,4-triazole, has been synthesized. The crystal and molecular structure has been solved at 298 K by single-crystal X-ray analysis. The compound crystallizes in the triclinic space group P1BAR, with a = 10.2233(2), b = 9.2247(2), c = 13.6153(2) angstrom, alpha = 113.1441(2), beta = 105.1 577(l), gamma = 91.2530(2)-degrees and Z = 1 (trinuclear unit). The least-squares refinement based on 3091 significant reflections converged to R = 0.0362 and R'= 0.0424. A linear array of three copper(II) ions, with two crystallographically independent copper(II) atoms is the basis for this structure. The copper(II) ions are bridged by two H-2ahmt ligands co-ordinating via N1 and N2 and an asymmetric chloride bridge [Cu(l)-Cl(l ) 2.296(l), Cu(2)-Cl(l) 2.688(l ), Cu(l )-CI(l )-Cu(2) 91.09(4)-degrees]. The Cu(l) ... Cu(2) distance is 3.5682(5) angstrom. The co-ordination geometry around the terminal copper(II) ions is completed by a non-bridging monodentate H-2ahmt ligand co-ordinating via N1, a chloride atom and a hydroxyl group from one of the two bridging H-2ahmt ligands. Magnetic susceptibility measurements (6.5-295 K) are in accord with the trinuclear nature of this compound and could be fitted for an antiferromagnetic interaction (g = 2.00 and J = -16.9 cm-1) between nearest neighbour copper(II) ions. The X- and Q-band powder EPR spectra are typical for a spin doublet. The presence of two different copper(II) chromophores is evident from the broad asymmetric band in the ligand field spectrum.