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

Abstract

A pentacoordinate monomeric Cu II complex, [Cu(H 2O)(H L 1)( L 2)](NO 3)(H 2O) ( 1), with the mixed ligands (where H 2 L 1=pyridine-2,6-dicarboxylic acid and L 2=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 Cu II center has a CuN 3O 2 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 H L 1 occupying the axial site. The H 2 L 1 ligand is mono-deprotonated in this structure, and only one oxygen atom of the carboxylate group coordinates to the Cu II 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.