Palladium (II) complexes with thione and thioalkylated thiosemicarbazones: Electrochemical, antimicrobial and thermogravimetric investigations

Spectrochim Acta A Mol Biomol Spectrosc. 2020 Aug 15:237:118358. doi: 10.1016/j.saa.2020.118358. Epub 2020 Apr 13.

Abstract

Four methoxy substitute salicylidene thiosemicarbazones were synthesized. The reaction of both thione and thioalkylated thiosemicarbazones with PdCl2 in ethanol yields ONS-coordinated chelate complexes with general formula [Pd(L)Cl]. The structures of eight compounds were characterized by using analytical and spectroscopic methods. Electrochemistry of the Pd(II) complexes was studied using cyclic voltammetric technique. The CVs of the complexes were quite complicate because of some oxidative responses of the ligands which proceed by forming conjugated -N=CH-, -HC=CH- and -N=CH-HC=CH- groups. Two cathodic responses attributed to one electron reduction of Pd(II)/(I) and Pd(I)/(0) were observed for the central ion coordinated with S atom of H3C-S- group whereas only one reduction peak appeared when the Pd(II) coordinated with S atom of >C=S group of thiosemicarbazone ligand. The latter also showed an additional anodic response assigned to Pd(II)/(III) oxidation. Thermogravimetric analysis (TGA) technique was used to investigate and compare the thermal properties of the ligands and their metal complexes. In vitro antimicrobial activity of thiosemicarbazones and their complexes was evaluated against four Gram-negative bacteria, three Gram-positive bacteria, and antifungal activity against three fungi.

Keywords: Antimicrobial activity; Electrochemistry; Palladium(II); TGA; Thiosemicarbazone.

MeSH terms

  • Anti-Bacterial Agents / chemical synthesis
  • Anti-Bacterial Agents / chemistry*
  • Anti-Bacterial Agents / pharmacology*
  • Antifungal Agents / chemical synthesis
  • Antifungal Agents / chemistry
  • Antifungal Agents / pharmacology
  • Coordination Complexes / chemical synthesis
  • Coordination Complexes / chemistry*
  • Coordination Complexes / pharmacology*
  • Crystallography, X-Ray
  • Drug Evaluation, Preclinical
  • Electrochemical Techniques
  • Gram-Negative Bacteria / drug effects
  • Gram-Positive Bacteria / drug effects
  • Magnetic Resonance Spectroscopy
  • Microbial Sensitivity Tests
  • Molecular Structure
  • Palladium / chemistry*
  • Spectrometry, Mass, Electrospray Ionization
  • Spectrophotometry, Ultraviolet
  • Thiones / chemistry
  • Thiosemicarbazones / chemistry

Substances

  • Anti-Bacterial Agents
  • Antifungal Agents
  • Coordination Complexes
  • Thiones
  • Thiosemicarbazones
  • Palladium