Synthesis and spectroscopic characterisation of copper(II) complexes with 5-methyl-1-(2′-pyridyl) pyrazole-3-carboxamide (MPyPzCA):: X-ray crystal structure of [Cu(MPyPzCA)2(H2O)](ClO4)2

The coordination mode of the title ligand, MP(y)P(z)CA (synthesised for the first time and characterised by elemental analyses, mass, IR and PMR spectral parameters), is reported by solid state isolation and physicochemical identification of copper(II) complexes, Cu(MP(y)P(z)CA)(2)X-2.H2O (X=Cl/Br/NO3/ClO4). Magnetic and electronic spectral features classify the reported complexes as six coordinate distorted octahedral ones. IR spectra (4000-200 cm(-1)) of MP(y)P(z)CA and its complexes indicate different denticity of the two ligand moities namely neutral bidentate function through pyrazolyl N-2 and pyridyl N-1' of one ligand (A) and the neutral tridentate behaviour through pyrazolyl N-2, pyridyl N-1' and the amidic oxygen of the second ligand system (B). The sixth apical coordination site is occupied by a water molecule in the perchlorate complex (as evident by X-ray data) or by the counter ion, X (X=Cl/Br/NO3). The electrochemical studies demonstrate easy oxidative nature of Cu(II) in the reported species. X-ray crystallographic studies of the perchlorate complex, [Cu(MP(y)P(z)CA)(2)(H2O)] (ClO4)(2), (Pna2(1), orthorhombic), has substantiated the conjecture that the geometry is distorted octahedral. The Cu-N (pyrazolyl) and Cu-N (pyridyl) bond lengths are 2.001(3) and 1.969(3) Angstrom and 2.020(4) and 2.206(4) Angstrom in the ligand systems, A and B. respectively; Cu-O (amidic oxygen) for ligand system B and Cu-O (water) bond lengths are 2.783(3) and 2.010(3) Angstrom, respectively. The crystal structure is highly stabilised through extensive hydrogen bonding. (C) 1999 Elsevier Science Ltd. All rights reserved.