Norfloxacin La(III)-based complex: synthesis, characterization, and DNA-binding studies

Abstract

A La(III) complex, [La^IIICl₂(NOR)₂]Cl (2), containing norfloxacin (NOR) (1), a synthetic fluoroquinolone antibacterial agent, has been synthesized and characterized by elemental analysis, IR, UV–vis spectra and ¹H NMR spectroscopy, and molar conductance measurements. The interaction between 2 and CT-DNA was investigated by steady-state absorption and fluorescence techniques in different pH media, and showed that 2 could bind to CT-DNA presumably via non-intercalative mode and the La(III) complex showed moderate ability to bind CT-DNA compared to other La(III) complexes. The binding site number n, and apparent binding constant K_A, corresponding thermodynamic parameters ΔG^#, ΔH^#, ΔS^# at different temperatures were calculated. The binding constant (K_A) values are 0.23 ± 0.05, 0.56 ± 0.05, and 0.18 ± 0.08 × 10⁵ L mol⁻¹ for pH 4, 7, and 11, respectively. It was also found that the fluorescence quenching mechanism of CT-DNA by La(III) complex was a static quenching process.

Graphical Abstract

Keywords:

• La(III) complexes
• Norfloxacin
• DNA-binding
• Fluorescence spectra
• Excitations

Acknowledgment

Helpful discussions with Prof Dr M.E. El-Khouly, University of Kafrelsheikh, Egypt is acknowledged.

Disclosure statement

No potential conflict of interest were reported by the authors.

Notes

Dedicated to Professor Rudi van Eldik on the occasion of his 70th birthday.