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Abstract
A series of cobalt(II) and copper(II) complexes of (2-acetylpyridine)-(5,6-diphenyl-[1,2,4]triazin-3-yl) hydrazone, APyTHy, L, having the formulae [LMCl2]·nH2O, [L2Cu(H2O)2](ClO4)2 and [L2M]X2·nH2O (X = ClO4 or OAc; M = Co or Cu and n = 0, 2 or 4) were isolated and characterized by elemental analysis, molar conductance, magnetic moment and IR, electronic and ESR spectral measurements. The IR spectra indicate that APyTHy behaves as a neutral tridentate ligand, coordinating via a triazine-N, azomethine-N and pyridine-N, except for [LCuCl2] and [L2Cu]X2·nH2O (X = OAc or ClO4), where it acts as a bidentate, not using the triazine-N in complexation. The magnetic moment and electronic spectral data suggest a distorted octahedral structure for 1 : 2 Co(II) complexes, a tetrahedral geometry for 1 : 2 Cu(II) complexes and a trigonal bipyramidal structure for [LCu(H2O)2](ClO4)2 and [LMCl2]·nH2O (M = CoII or CuII; n = 0 or 2) complexes. Upon heating the green [LCuCl2]·2H2O, brown square planar [LCuCl2] was produced. The mixing coefficients and covalency factors for the copper(II) complexes estimated from the combined X-band ESR g-values and electronic d–d transitions using Reinen's method imply that the CuN3X2 chromophore is considerably distorted towards square pyramidal.