Synthesis, crystal structure, EPR and electrochemical studies of copper(II) dipicolinate complex with 2,2′-dipyridylamine ligand

The (2,2′-dipyridylamine)(pyridine-2,6-dicarboxylato)copper(II) trihydrate complex was synthesized and characterized by spectroscopic (IR, UV–vis, EPR), X-ray diffraction technique and electrochemical methods. The copper(II) center is surrounded by one bidentate 2,2′-dipyridylamine (dpa) and one tridentate dipicolinate (dpc) ligand, and exhibits a distorted square-pyramidal geometry. The crystal packing involves both hydrogen-bonding and π–π interactions. The solvent water molecules link monomers to one another through hydrogen-bonding interactions, forming ladder-type chains in the ab plane. π–π interactions also occur between the dpa rings of neighboring molecules and are responsible for interchain packing. Based on EPR and optical absorption studies, spin-Hamiltonian and bonding parameters have been calculated. The g-values, calculated for title complex in polycrystalline state at 298 K and in frozen DMF (110 K), indicate the presence of the unpaired electron in the dx2-y2dx2-y2 orbital. The evaluated metal–ligand bonding parameters showed strong in-plane σ- and π-bonding. The cyclic voltammogram of the title complex investigated in DMF (dimethylformamide) solution exhibits only metal centered electroactivity in the potential range ±1.25 V versus Ag/AgCl reference electrode.