Regularities in the stabilization by hemoglobin of binuclear iron complexes [Fe2(μ-N—C—SR)2(NO)4] containing benzimidazolylthiol and benzothiazolylthiol ligands

The NO-donor ability of new binuclear tetranitrosyl complexes of the μ-N—C—S type, namely, bis(5-methylbenzimidazol-2-ylthio)- (1), bis(benzimidazol-2-ylthio)- (2), and bis(benzothiazol-2-ylthio)(tetranitrosyl)diiron (3), was studied in aqueous solutions by spectrophotometry. All kinetic regularities obtained for complexes 1–3 are well described in terms of formalism of pseudo-first-order reactions. The apparent first-order reaction rate constants for NO evolution by the complexes to solution were determined. Complexes 1–3 are good donors of NO. The structures of the complexes and the effect of their stabilization by hemoglobin were compared. The stabilization effect is explained by different basicities of the sulfur-containing ligands in the complexes studied.