Ni(II)-tetrahedral complexes: Characterization, antimicrobial properties, theoretical studies and a new family of charge-transfer transitions

A new amine containing selenium and their five imine, (SeSchX)(X: -H, F, Cl, Br, CH3), and Ni (II) complexes, [Ni(SeSchX)(H2O)2]Cl/[Ni(SeSchCl)(H2O)Cl], were synthesized. The compounds were characterized by means of elemental analyses, 13C and 1H NMR (for imine), FT-IR, UV–Visible spectroscopy, TGA/DTA and elemental analyses. [Ni(SeSchCl)(H2O)Cl] complex from Ni(II) complexes changes color from yellow to orange in the range pH 5–7. [Ni(SeSchCl)(H2O)Cl] complex has ligand-to-metal charge-transfer (LMCT) transitions in the basic medium. Excitation characteristics and energetic of [Ni(SeSchCl)(H2O)Cl] complex, examined via TD-DFT calculations, reveals transitions of LMCT and π → π* character that matches the experimental values. [Ni(SeSchCl)(H2O)Cl] complex showed the highest antibacterial activity when compared to other complexes reported in this work.

Graphical abstractFive new Schiff bases involving Selenium [(SeSchX)(X: -H, F, Cl, Br, CH3)] and Ni(II) complexes ([Ni(SeSchX)(H2O)2]Cl/[Ni(SeSchCl)(H2O)Cl]) are synthesized and characterized. [Ni(SeSchCl)(H2O)Cl] complex exhibits metal-centered color-changing in between pH 5–7 and is a more potent bactericide than other complexes.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Novel Ni(II)-tetrahedral complex with selenium ligand has been synthesized by means of template method and characterized. ► [Ni(SeSchCl)(H2O)Cl] complex shows different properties of synthesized Ni(II) complexes. ► This complex changes color from yellow to orange in the range pH 5–7. ► [Ni(SeSchCl)(H2O)Cl] complex is more potent bactericides than all of the substances synthesized.