Structural elucidation of new ferrocene appended scaffold and their metal complexes: Comparative in vitro DNA/BSA binding and antibacterial assay

Abstract

A new organometallic ligand (L) was designed and synthesized from ferrocenecarboxaldehyde and 2–Aminobenzophenone through the condensation reaction in one step process. The metal complexes of this L with the formula [Zn(L)2](NO3)2 (1), [Cu(L)2](NO3)2 (2) and [Co(L)2](NO3)2 (3) were synthesized in high yield. The ligand (L) and complexes 1–3 were completely characterized by elemental analysis, spectroscopic and spectrometric techniques such as FT–IR, ToF Mass,1H NMR,13C NMR molar conductance and magnetic moment measurements. The spectroscopic interpretation showed that complex 1 and complex 3 prefer tetrahedral geometry whereas complex 2 adopts a square planar arrangement around the copper(II) ion. The in vitro DNA interaction studies of ligand (L) and metal complexes 1–3, were performed by UV–Vis absorption, fluorescence spectral and ethidium bromide displacement experiments. The absorption studies of complexes 1–3 reveal the existence of both hyperchromic and hypochromic effect which indicated the mixed type of binding that is intercalation of the aromatic part and the electrostatic surface interaction of metal ions with DNA phosphate groups. A comparison of binding constant Kb values suggested the stronger binding of complex 2 (Kb = 6.17 × 104 M−1) as compared to L and complexes 1 and 3. Furthermore, in vitro BSA binding studies and FRET also suggests greater interaction of complex 2 with BSA causing modulations in the hydrophobic microenvironment near Trp-212 in the subdomain IIA pocket by static quenching mechanism. Interestingly, all three complexes 1–3 tested showed promising antimicrobial activity as revealed by the disc diffusion assay in all four human pathogenic bacterial species comprising both gram–positive and gram–negative bacteria.