Equilibria between iron-dinitrosy paramagnetic species in aqueous and alcoholic solutions studied by magnetic resonance spectroscopy

Abstract

Equilibria between different types of iron-dinitrosyl complexes in solution were studied by means of ESR and NMR spectroscopy. The dependence of pH and temperature of the ESR parameters and the variations in the nuclear hyperfine structure in ethanol solution were explained by the existence of three paramagnetic species: [Fe(NO)₂(C₂H₅OH)₂]⁺; [Fe(NO)₂(C₂H₅OH)(C₂H₅O)]° and [Fe(NO)₂(C₂H₅O)₂]^–. Similar results were obtained in water solution. Finally the equilibrium was studied in presence of a ligand (bromide ion). Changes in the ESR spectra, obtained by varying pH and ligand concentration, give evidence that five different paramagnetic complexes participate at the equilibrium.