Reaction of a model siderophore with Ni(II), Co(II) and Zn(II) in aqueous solution: kinetics and spectroscopy.

Abstract A spectroscopic study was performed showing that the [Fe(III)(L 2− ) 2 ] 1− (L 2−  = dopacatecholate) complex reacts with Ni(II), Co(II) and Zn(II) in an aqueous solution containing S 2 O 3 2 - resulting in the soluble [M(L 1− ) 3 ] 1− (L 1− = dopasemiquinone; M = Ni(II), Co(II) or Zn(II) complex species. The Raman and IR spectra of the [CTA][M(L 1− ) 3 ] complexes, CTA = hexadecyltrimethylammonium cation, in the solid state were obtained. The kinetic constants for the metal substitution reactions were determined at four different temperatures, providing values for Δ H ≠ , Δ S ≠ and Δ G ≠ . The reactions were slow ( k  = 10 −11  M s −1 ) and endothermic. The system investigated can be considered as a simplified model to explain some aspects of siderophore chemistry.