Synthesis, spectroscopic characterization, DNA cleavage and antibacterial studies of a novel tridentate Schiff base and some lanthanide(III) complexes

A novel potential tridentate Schiff base was prepared by condensing equimolar quantities of 2-hydroxyacetophenone and 2-aminopyrimidine in methanol. This ligand was versatile in forming a series of complexes with lanthanide ions such as La(III), Pr(III), Nd(III), Sm(III), Gd(III), Dy(III) and Yb(III). The ligand and the metal complexes were characterized through elemental analysis, molar conductance, UV-Visible, IR, 1H NMR, and mass spectral studies. The spectral studies indicated that the ligand was coordinated to the metal ion in neutral tridentate fashion through the azomethine nitrogen, one of the nitrogen atoms in the pyrimidine ring and the phenolic oxygen without deprotonation. Thermal decomposition and luminescence property of lanthanum(III) complex were also examined. The X-ray diffraction patterns showed the crystalline nature of the ligand and its lanthanum(III) complex. The DNA cleavage studies of the ligand and the metal complexes were carried out and it was observed that the lanthanum(III) and neodymium(III) complexes cleaved the pUC19 DNA effectively. The ligand and the metal complexes were screened for their antibacterial activities. The metal complexes were found to be more potent bactericides than the ligand. Cleavage of supercoiled pUC19 DNA (0.5 μg) by complexes in a buffer containing 50 mmol/L Tris-HCl at 37 °C (30 min): lane M: marker; lane control: DNA control; lane L: DNA+Ligand; lane P-V: complexes of lanthanum(III), samarium(III), neodymium(III), praseodymium(III), gadolinium(III), dysprosium(III) and ytterbium(III)