Receptor-Mediated and Hydrolytic Denitrosylation of Dinitrosyl Iron Complexes to Yield Amorphous FexOy and its Photoinduced Transformation into Crystalline Fe@FexOy Nanoparticles

In this study, denitrosylation of amine-bound {Fe(NO)2}10 [(2-A)Fe(NO)2] (amp-DNIC) was explored to occur through (a) receptor-mediated transfer of ·NO/[NO]- to [Mn(TPP)(Cl)] and (b) a hydrolytic process leading to the liberation of ·NO together with N2O. In the presence of the bifunctional ·NO/[NO]−-receptor [Mn(TPP)(Cl)] (TPP = 5,10,15,20-tetraphenyl-21H,23H-porphine), amp-DNIC acts as a dual ·NO/[NO]− delivery reagent for the conversion of [Mn(TPP)(Cl)] into [Mn(TPP)(NO)] and [Mn(TPP)(NO)2]. Alternatively, incubation of amp-DNIC in an acetonitrile solution containing 5% deaerated water resulted in its hydrolytic transformation into amorphous FexOy particles (amp-1) accompanied by the release of ·NO (∼75%), N2O (∼10%), and nitrite (∼6%). Upon irradiation of amp-DNIC in the presence of the photosensitizer Eosin Y and the sacrificial reductant TEA, the formation of cubic and crystalline Fe@FexOy core-shell composite carbonaceous material (amp-2) was characterized by high-resolution X-ray diffraction (HRXRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge spectroscopy (XANES), and extended X-ray absorption fine structure (EXAFS). Based on the mechanisms described above, the hydrolytic transformation of amp-DNIC into amp-1 occurred, followed by the photoinduced structural rearrangement of amp-1, amorphous FexOy particles, into amp-2, the cubic and crystalline Fe@FexOy core-shell composite carbonaceous material.