Bio-active mixed ligand Cu(II) and Zn(II) complexes of pyrimidine derivative Schiff base: DFT calculation, antimicrobial, antioxidant, DNA binding, anticancer and molecular docking studies

Abstract

A new series of bio active Cu(II) and Zn(II) complexes [CuL(phen)](OOCCH₃) (<b>1</b>), [ZnL(phen)](OOCCH₃) (<b>2</b>), [CuL(bpy)](OOCCH₃) (<b>3</b>), [ZnL(bpy)](OOCCH₃) (<b>4</b>) have been synthesized using the pyrimidine derivative Schiff base (<b>HL</b>) [<b>HL</b> = 2-(4,6-dimethylpyrimidin-2-ylimino)methyl)-4-nitrophenol], 1,10-phenanthroline (phen), 2,2'-bipyridine (bpy) and acetate salts of Cu(II) and Zn(II). UV-Visible, FT-IR, ¹H-NMR, ESR, elemental analysis, molar conductance and EI-MS spectral techniques have been used to endorse the square planar geometry for the complexes <b>1</b>-<b>4</b>. The optimized molecular structure and the harmonic vibrational frequencies have been scrutinized by DFT methods. The antibacterial and antifungal activity of Schiff base (<b>HL</b>) and complexes <b>1</b>-<b>4</b> indicates that complex <b>1</b> acts as good antimicrobial agent against microbial strains than <b>HL</b>, complexes <b>2</b>-<b>4</b> and standard drugs streptomycin and nystatin. DNA cleavage study of the complexes <b>1</b>-<b>4</b> exposes that complexes <b>1</b> and <b>3</b> spectacle good cleaving agent than complexes <b>2</b> and <b>4</b>. The interaction of complexes <b>1</b>-<b>4</b> with CT DNA using absorption, emission and viscometric measurements signifies that complexes <b>1</b>-<b>4</b> bind <i>via</i> an intercalation mode. The highest binding constants (<i>K</i>_b) for the complex <b>1</b> is confirmed as 7.83 × 10³ M^-1 and 2.98 × 10⁴ M^-1 by absorption and emission spectrum respectively. These experimental observations were found to be close to the theoretical observations investigated by the molecular docking technique. Antioxidant property of the complexes <b>1</b>-<b>4</b> using DPPH assay clinches that complex <b>1</b> produces significant scavenging effect than other compounds. The result of <i>in vitro</i> cytotoxicity of the Schiff base (<b>HL</b>) and complexes <b>1</b>-<b>4</b> shows that complex <b>1</b> shows better ability to inhibit the growth of cancer cells. Communicated by Ramaswamy H. Sarma.