Purine-based Schiff base Co(II), Cu(II), and Zn(II) complexes: Synthesis, characterization, DFT calculations, DNA binding study, and molecular docking

A series of metal complexes of Co(II), Zn(II), and Cu(II) of purine base Schiff base ligand L1 6,6 '-((1E,1 ' E)-((7Hpurine-2,6-diyl)bis(azanylylidene))bis(methanylylidene))bis(2-methoxyphenol) and L2 3,3 '-((1E,1 ' E)-((7H-purine-2,6-diyl)bis(azanylylidene))bis (methanylylidene))bis(4H-chromen-4-one) were synthesized. The characterization of synthesized compounds was investigated through elemental analysis, UV-vis, FT-IR, NMR, and mass spectrometry. The spectroscopic and DFT studies validate the coordination of ligand to the metal centers along with their structural details. In complexes of L1 and L2, the N and O atoms coordinate to metal centers of zinc, cobalt, and copper. However, in the case of L1 complexes the binding mode of oxygen is through phenolic -OH of vanillin moiety. In contrast, complexes of L2 the binding mode of oxygen source is carbonyl oxygen of chromone carboxaldehyde moiety. The stability order follow- ZnL1 < CoL1 < CuL1 < CuL2 < CoL2 < ZnL2. The CT-DNA binding activity of all synthesized complexes with the help of UV-vis absorption titration, fluorescence titration, and viscosity measurement was studied. In both cases, cobalt complexes of L1 and L2 showed high DNA binding activity. The binding constant values are in the order of 105 via intercalation mode of binding. The molecular docking study was performed to speculate on the active binding site between metal complexes and CTDNA.

Automated summary

Metal complexes of Co(II), Zn(II), and Cu(II) with purine base Schiff base ligands L1 and L2 were synthesized and characterized. The coordination of the ligands to the metal centers and their structural details were confirmed through spectroscopic and DFT studies. The binding modes of oxygen atoms in L1 and L2 complexes were found to be different. Cobalt complexes of L1 and L2 showed high DNA binding activity, with a binding constant in the order of 105 via intercalation mode. Molecular docking study provided insights into the active binding site between the metal complexes and CT-DNA.