Experimental and quantum chemical study of transformations of a binuclear iron nitrosyl complex with a substituted mercaptotriazole ligand in DMSO

The process of transformation of the water-insoluble binuclear iron nitrosyl complex [Fe₂(SC₂N₃C₆H₄NO₂)₂(NO)₄] (1) in DMSO was studied. Using UV-vis spectrophotometry, it was shown that complex 1 decomposes in the solution. The theoretical electronic spectrum in the UV and visible regions was calculated for this complex using a TDDFT method, and an analysis of molecular orbitals of the complex was carried out. It was suggested that the disappearance of the absorption band due to an electronic transition involving the Fe—NO groups is associated with the NO donation. Using quantum chemical calculations, a total energy diagram of the decomposition of complex 1 in DMSO was obtained, and two mechanisms of its transformation, viz., one proceeding through an increase in the coordination number of the iron atom to 6 and the other occurring with breaking the Fe—S bonds with the μ-SCN bridge, were studied.