Binding interaction of a heteroleptic silver(I) complex with DNA: A joint experimental and computational study

Abstract

A new heteroleptic Ag(I) complex formulated as [Ag(daf)(phen)]NO3, where daf and phen stand for 4,5-diazafluoren-9-one and 1,10-phenanthroline, respectively, has been prepared and structurally characterized by elemental analysis, spectroscopic methods (IR, 1HNMR, and UV–Vis) and cyclic voltammetry. The geometry optimization around Ag(I) at the level of DFT has demonstrated that the Ag(I) center has been nested in a tetrahedral N4 coordination geometry which found to be in close agreement with the experimentally proposed structure. The bond lengths, angles, and the HOMO/LUMO energies have been calculated to substantiate the geometry of the complex. The DNA binding property of the Ag(I) complex has been explored in detail both theoretically (DFT and molecular docking) and experimentally (UV–Vis absorption spectroscopy, circular dichroism spectroscopy, luminescence quenching, competitive binding with ethidium bromide, cyclic voltammetry, and gel electrophoresis), indicating the good affinity of the Ag(I) complex for the intercalation (Kb (binding constant) = 3.45 × 105 M−1). Providing a fuller picture of Ag(I) complex–DNA interaction, the energy-minimized structure of the complex has been docked to the DNA with a d(AGACGTCT)2 sequence and the results are in close agreement with experimental achievements and make a deeper insight into the relationship between the structure and biological activity of the complex.