Ag(I) and Zn(II) isonicotinate complexes: design, characterization, antimicrobial effect, and CT-DNA binding studies

Abstract

Trinuclear Ag(I) (1) and dinuclear and mononuclear Zn(II) isonicotinate (2 and 3) complexes were prepared and characterized by X-ray crystallography, elemental analysis, IR spectroscopy, and thermal analysis. Single-crystal analysis of the Ag(I) complex reveals two different monodentate carboxylate coordination modes, protonated and deprotonated, respectively. IR spectra showed correlations between isonicotinate coordination modes and Δ(ν_as− ν_s)_IR values. In addition, the hydrogen bonds significantly influence a position of carboxylate absorption bands. Moreover, IC₅₀ and MIC data for bacteria, yeasts, and filamentous fungi were determined and the binding of Ag(I) and Zn(II) complexes to calf thymus DNA was investigated using electronic absorption, fluorescence, and CD measurements. Biological tests showed that the Ag(I) complex is more active than commercially used Ag(I) sulfadiazine against Escherichia coli. The fluorescence spectral results indicate that the complexes can bind to DNA through an intercalative mode. The Stern–Volmer quenching constants for investigated complexes obtained from the linear quenching plot are in the range of 1.67 × 10⁴–3.42 × 10⁴ M⁻¹.

Keywords:

• Ag(I) and Zn(II) complexes
• Isonicotinate
• Mid-IR spectra
• Antimicrobial activity
• Intercalative DNA binding
• Fluorescence

Acknowledgements

The authors are very grateful to Mária Vojtasová and Prof. Ján Imrich from NMR Laboratories, Department of Organic Chemistry, P.J. Šafárik University in Košice for the NMR spectra measurements.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Slovak Research and Development Agency [grant number APVV-0280-11]; Pavol Jozef Safarik University in Kosice [grant number VVGS PF-2015-488]; Ministry of Education of Slovak Republik [grant number VEGA 1/0535/16]; Ministry of Education of Slovak Republic [grant number VEGA 1/0001/13].