Receptor-Mediated and Hydrolytic Denitrosylation of Dinitrosyl Iron Complexes to Yield Amorphous Fe x O y and Its Photoinduced Transformation into Crystalline Fe@Fe x O y Nanoparticles

TL;DR

This study shows how dinitrosyl iron complexes can be transformed into amorphous and then crystalline iron oxide nanoparticles through chemical and light-induced processes.

Contribution

The paper introduces a novel dual mechanism for denitrosylation and the photoinduced transformation of iron complexes into structured nanoparticles.

Findings

Denitrosylation of amp-DNIC occurs via receptor-mediated transfer and hydrolysis, releasing ·NO, N2O, and nitrite.

Hydrolysis of amp-DNIC produces amorphous Fe x O y particles (amp-1) which transform into crystalline Fe@Fe x O y nanoparticles (amp-2) under light.

Characterization techniques confirmed the structural and compositional changes during the transformation process.

Abstract

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
Fe
x
O
y
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@Fe
x
O
y
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 Fe
x
O
y
particles, into amp-2, the
cubic and crystalline Fe@Fe
x
O
y
core–shell composite carbonaceous material.

Figures