Spectroscopic characterization, X-ray structure, antimicrobial activity and DFT calculations of novel dipicolinate copper(II) complex with 2,6-pyridinedimethanol

Novel dipicolinate complex of copper(II) ion, [Cu(dmp)(dpc)]·0.8H2O [dmp: 2,6-pyridinedimethanol; dpc: dipicolinate or pyridine-2,6-dicarboxylate], has been prepared and fully characterized by single crystal X-ray structure determination. The central copper(II) ion is bonded to dpc and dmp ligands through pyridine nitrogen atom together with two oxygen atom, forming the distorted octahedral geometry. The complex molecules, connected via O–H⋯O hydrogen bonds, form a supramolecular structure. H2dpc, [Cu(dpc)(H2O)3] and [Cu(dmp)(dpc)]·0.8H2O were screened for antimicrobial activity against Gram-positive, Gram-negative bacteria and yeast. H2dpc and [Cu(dpc)(H2O)3] exhibited antibacterial and antifungal activity, while [Cu(dmp)(dpc)]·0.8H2O exhibited activity only for Gram-positive bacteria. The geometry optimization and EPR parameters were carried out using the following unrestricted 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 electronic station in the frontier orbitals of the copper complex calculated from the experimental data is compared to the results of time-depended DFT calculations with the polarizable continuum model. Calculated vibrational frequencies are consistent with the experimental IR data.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The complex molecules, connected via O–H⋯O hydrogen bonds, form a supramolecular structure. ► [Cu(dmp)(dpc)]·0.8H2O were screened for antimicrobial activity against Gram-positive, Gram-negative bacteria and yeast. ► The geometry optimization and EPR parameters were carried out using the unrestricted hybrid density functionals.