Synthesis, characterization and antioxidant activity of new copper(i) complexes of scorpionate and water soluble phosphane ligands

Abstract

New copper(I) complexes have been synthesised from the reaction of CuCl with potassium hydrotris(4-bromo-1H-pyrazol-1-yl)borate, KTp^4Br or lithium bis(3,5-dimethylpyrazol-1-yl)acetate, Li[L₂CO₂] ligands and 4- or 2-(diphenylphosphane)benzoic acid or tris(m-sulfonatophenyl)posphine trisodium salt (TPPTS) coligands. The complexes obtained have been characterized by elemental analyses and FT-IR in the solid state, and by NMR (¹H and ³¹P{¹H}) and electrospray mass spectrometry (ESI-MS) in solution. Single crystal structural characterisation was undertaken for the {Cu[PPh₂(4-C₆H₄COOH)](Tp^4Br)} derivative, an interesting dimeric supramolecular assembly. A chemiluminescence study has demonstrated the superoxide scavenging activity of these new copper complexes. The Comet assay was used to evaluate the impairment of DNA in rat epithelial cells exposed to different reactive nitrogen species. In addition, the same complexes were included in this study to determine their efficacy as antioxidants in mitigating oxidative DNA damage. The parameter tail moment, used as an index of DNA damage, showed that the complex {Cu[PPh₂(4-C₆H₄COOH)](Tp^4Br)} remarkably inhibited DNA strand breaks induced by the different nitrogen oxide species. The other copper complexes under study showed a different ability to reduce tail moment values depending on the type of RNOS donor used.