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Paper
Dalton Trans., 2007, 5268 - 5274, DOI: 10.1039/b710076k
Formation of a triply bridged µ-oxo diiron(III) core stabilized by two deprotonated carboxamide groups upon photorelease of NO from a {Fe–NO}6 iron nitrosyl
Aura A. Eroy-Reveles, C. Gianna Hoffman-Luca and Pradip K. Mascharak
The iron nitrosyl [(PaPy2Q)Fe(NO)](ClO4)2 ( 2), derived from the quinoline-based ligand PaPy2QH (N,N-bis(2-pyridylmethyl)amine-N-ethyl-2-quinoline-2-carboxamide, where H is dissociable proton) has been characterized by spectroscopy and X-ray diffraction techniques. The 1H NMR spectrum (S = 0 ground state) and
NO value of 1885 cm–1 indicate that 2 is a {Fe–NO}6 nitrosyl. Although 2 is stable in the dark, exposure of an acetonitrile solution of 2 (
max = 510 nm) to light in the visible range causes rapid release of NO and formation of the solvato species [(PaPy2Q)Fe(MeCN)](ClO4)2 ( 6). Quantum yield (
) measurements indicate that 2 is a more efficient NO donor ( = 0.258) than [(PaPy3)Fe(NO)](ClO4)2 ( 1, = 0.185), a complex derived from a similar but pyridine-based ligand. Interestingly, when the photoproduct 6 is exposed to water or a small amount of base, the triply bridged diiron(III) species [(PaPy2Q)FeOFe(PaPy2Q)](ClO4)2 ( 3) forms in good yield. This species can be independently synthesized from aerobic oxidation of the Fe(II) species [(PaPy2Q)Fe(MeCN)](ClO4) in acetonitrile. The structure of 3 reveals a unique Fe(III)–O–Fe(III) link supported by two (
2,µ2)µ-
NCO
bridges derived from the carboxamido groups of the two (PaPy2Q)Fe(III) moieties.
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