A combined crystallographic, spectroscopic, antimicrobial, and computational study of novel dipicolinate copper(II) complex with 2-(2-hydroxyethyl)pyridine

Novel dipicolinate complex of copper(II) ion, [Cu(hepy)(dpc)H2O] [hepy: 2-(2-hydroxyethyl)pyridine; dpc: dipicolinate or pyridine-2,6-dicarboxylate], was prepared and fully characterized by single crystal X-ray structure determination. [Cu(hepy)(dpc)H2O] was investigated for antimicrobial activity against a fungal strain, Gram-positive, and Gram-negative bacteria. The compound was found to be active against of all microorganisms (MIC values 512-1,024 mu g mL(-1)). The mixed-ligand copper(II) complex was satisfactorily modeled by calculations based on following hybrid density functionals: LSDA, BPV86, B3LYP, B3PW91, MPW1PW91, PBEPBE, and HCTH. Although the supramolecular interactions have some influences on the molecular geometry in solid state phase, calculated data show that the predicted geometries can reproduce the structural parameters. The performance of these functional approaches for the calculation of electron paramagnetic resonance hyperfine coupling constant Cu2+ ion was evaluated critically by comparison with experimental data. The g values obtained from density functional theory (DFT) calculations were in compatible with the experimental results, whereas the A values were not. Electronic structure of the complex was calculated using time-dependent DFT method with the polarizable continuum model. Descriptions of frontier molecular orbitals and the relocation of the electron density of the compound were determined. Because the calculations of vibrations were carried out in gaseous phase there were shifts in vibration frequencies above 3,000 cm(-1).