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Keywords:

  • Redox chemistry;
  • Reduction;
  • Electron transfer;
  • Kinetics;
  • Antiprotozoal agents;
  • DNA cleavage;
  • Ruthenium

Abstract

The kinetics of the reduction of [RuIII(hedtra)(pz)] (hedtra3– = N-hydroxyethylethylenediaminetriacetate; pz = pyrazine) by biologically important reducing agents, Red (Red = L-ascorbic acid, catechol and cysteine), resulting in the formation of the corresponding red-coloured ruthenium(II) complex has been studied spectrophotometrically using both conventional mixing and stopped-flow techniques. The time course of the reaction was followed as a function of [Red], pH and temperature. Alkali metal ions were found to have an insignificant effect on the reaction rate. Kinetic data and activation parameters are interpreted in terms of an outer-sphere electron-transfer mechanism, and discussed with reference to the data reported for the corresponding RuIII–edta (edta4– = ethylenediamineteraacetate) complex. The antibacterial activity of the [RuIII(hedtra)(pz)] complex in inhibiting the growth has been explored. Results of the biological studies have been discussed in terms of the cleavage of chromosomal DNA of the bacteria by the [RuIII(hedtra)(pz)] complex in the presence of cysteine under aerobic conditions.