A hydrogen-bonded 3D coordination network of CuII nitrate with pyridine-2,6-dicarboxylic acid and 3-(2-pyridyl)pyrazole: hydrothermal synthesis, characterization and crystal structure

A pentacoordinate monomeric CuII complex, [Cu(H2O)(HL1)(L2)](NO3)(H2O) (1), with the mixed ligands (where H2L1 ¼ pyridine-2,6- dicarboxylic acid and L2 ¼ 3-(2-pyridyl)pyrazole), has been synthesized and characterized by elemental analyses, IR, thermogravimetric analysis and X-ray diffraction techniques. X-ray structural analysis of complex 1 revealed that the CuII center has a CuN3O2 distorted square pyramid environment with three N atoms of two different ligands and an O atom of coordinated water molecule constituting the mean plane, and one O atom of ligand HL1 occupying the axial site. The H2L1 ligand is mono-deprotonated in this structure, and only one oxygen atom of the carboxylate group coordinates to the CuII center. A striking structural feature of complex 1 is the three-dimensional supramolecular architecture formed through intermolecular C–H· · ·O, O–H· · ·O and N–H· · ·O hydrogen-bonding interactions. The IR and ESR spectra, and thermogravimetric analysis of complex 1 have been further investigated. q 2004 Elsevier B.V. All rights reserved.