Cobalt(II) and copper(II) complexes of (2-thiophene)-(5,6-diphenyl-[1,2,4]-triazin-3-yl)hydrazone

Abstract

New complexes having the formulae [L2CoX2] and [LCuCl2], [LCuCl] and [LCu](ClO4)2 where L = (2-thiophene)-(5,6-diphenyl-[1,2,4]-triazin-3-yl)hydrazone TDPTH; X = Cl, OAc or ClO4 have been synthesized and characterized on the basis of elemental analyses, conductance, magnetic moments and infrared, electronic and ESR spectral data. The IR spectra indicate that TDPTH is a neutral bidentate ligand, coordinating via a triazine-N and azomethine-N in [L2CoX2] and [LCuCl2] with the thiophene-S not coordinated but is tridentate in [LCuCl] and [LCu](ClO4)2 through the same two nitrogen atoms and thiophene-S. The magnetic moment and electronic spectral data suggest a distorted octahedral structure for Co(II) complexes, a dimeric square pyramidal geometry for [LCuCl2] through chloride bridges and a dimeric diamagnetic, four-coordinate copper in [LCu](ClO4)2 through thiophene-S bridges. The X-band ESR spectra of Co(II) complexes, in the solid state, are rhombic with three g values consistent with a high-spin distorted octahedral structure. The X-band ESR spectrum of the powdered sample of both [LCuCl2]·2H2O and [LCu](ClO4)2 at room temperature and at 77 K showed only one broad signal due to ΔM s = ± 1 transition and a weak signal due to the forbidden ΔM s = ± 2 transition, indicating an antiferromagnetic interaction between copper(II) centers whereas [LCuCl] is ESR silent, indicating a monovalent copper ion in this complex.