Synthesis, spectral, DFT calculation, antimicrobial, antioxidant, DNA/BSA binding and molecular docking studies of bio-pharmacologically active pyrimidine appended Cu(II) and Zn(II) complexes

Abstract

A new pyrimidine derivative Schiff base (HL) [HL = 2-((4-amino-6-chloropyrimidin-2-ylimino)methyl)-4-nitrophenol] has been synthesized using 2,6-diamino-4-chloropyrimidine and 5-nitrosalicylaldehyde. Transition metal complexes of Cu(II) and Zn(II) complexes [CuL(OAc)] (1), [ZnL(OAc)] (2) are prepared with HL/metal(II) acetate with molar ratio of 1:1. The Schiff base (HL) and the complexes 1 and 2 are evaluated by UV-Visible, 1H-NMR, FT-IR, EI-MS and ESR spectral techniques. Complexes 1 and 2 are confirmed as square planar geometry. Electrochemical studies of the complexes 1 and 2 are used to analyse the quasi reversible process. Density Functional Theory (DFT) using the B3LYP/6-31++G(d,p) level basis set was used to get the optimised geometry and non-linear optical properties. The complexes 1 and 2 are good antimicrobial agents than Schiff base (HL). The interactions of the HL and complexes 1 and 2 with Calf Thymus (CT) DNA are investigated by electronic absorption methods and viscosity measurements. Various molecular spectroscopy techniques, such as UV absorption and fluorescence, were used to explore the mechanism of interaction between the BSA and the ligand HL and complexes 1 & 2 under physiological settings. Complexes 1 and 2 are act as potential antioxidants than free Schiff base (HL) by DPPH radical scavenging assay. Furthermore, the purpose of the molecular docking studies was to better understand how metal complexes interact with biomolecules (CT-DNA and BSA). From these biological analyses, complex 1 acts as good intercalator with CT DNA & BSA and potent antioxidant with DPPH radical than complex 2. Communicated by Ramaswamy H. Sarma