Bio-active mixed ligand Cu(II) and Zn(II) complexes of pyrimidine derivative Schiff base: DFT calculation,...

A new series of bio active Cu(II) and Zn(II) complexes [CuL(phen)](OOCCH₃) (1), [ZnL(phen)](OOCCH₃) (2), [CuL(bpy)](OOCCH₃) (3), [ZnL(bpy)](OOCCH₃) (4) have been synthesized using the pyrimidine derivative Schiff base (HL) [HL = 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 1-4. The optimized molecular structure and the harmonic vibrational frequencies have been scrutinized by DFT methods. The antibacterial and antifungal activity of Schiff base (HL) and complexes 1-4 indicates that complex 1 acts as good antimicrobial agent against microbial strains than HL, complexes 2-4 and standard drugs streptomycin and nystatin. DNA cleavage study of the complexes 1-4 exposes that complexes 1 and 3 spectacle good cleaving agent than complexes 2 and 4. The interaction of complexes 1-4 with CT DNA using absorption, emission and viscometric measurements signifies that complexes 1-4 bind via an intercalation mode. The highest binding constants (K_b) for the complex 1 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 1-4 using DPPH assay clinches that complex 1 produces significant scavenging effect than other compounds. The result of in vitro cytotoxicity of the Schiff base (HL) and complexes 1-4 shows that complex 1 shows better ability to inhibit the growth of cancer cells. Communicated by Ramaswamy H. Sarma.