Redox potentials of iron-nitrosyl complexes: DFT calculations

Quantum chemical calculations of the structure and solvation energies of mono- and dianions of Roussin's red salt esters [Fe-2(mu-RS)(2)(NO)(4)] (R = Me, Et, Pr-i, Bu-t) in solutions in THF and acetonitrile were carried out. In monoanions, an additional electron is localized on one Fe(NO)(2) fragment, which leads to significant structural distortion of the anion compared to neutral molecule. The second electron is localized on the other Fe(NO)(2) fragment; this causes symmetrization of the dianion geometry. There are good linear correlations between the calculated and experimental redox potentials of these systems. A relationship was proposed for estimation of the redox potentials of related iron-nitrosyl complexes. The standard redox potentials of the complex with R = Ph in water, DMSO, and acetonitrile evaluated using this expression lie between -0.5 and -0.6 V.