Yb(III), Sm(III) and La(III) complexes of a tetradentate pyridoxal Schiff base ligand: Their DNA-binding activity and bio-imaging applications

Abstract

Yb(III), Sm(III) and La(III) complexes of a tetradentate Schiff base ligand, bis(pyridoxylidene)ethyelenediamine, are reported. Single crystal X-ray structures of the complexes reveal that in all the three complexes the Ln(III) ions are in a distorted dodecahedral geometry with N4O4-coordination environment provided by two coordinated ligands. Fluorescence spectroscopy shows that in the Yb(III) and Sm(III) complexes energy transfer from ligand centered excited state leads to population of an emissive f-f excited state. The complexes bind to ct-DNA, with high binding constant (Kb) comparable to those compounds (like ethydium bromide) which bind by intercalative mode. Cytotoxicity study shows that the complexes have quite low cytotoxicity towards HeLa cells. Further, they exhibited fast response, bright fluorescence and stability at physiological pH, making them suitable for use in fluorescence bio-imaging.