Photoinduced Release of Nitroxyl and Nitric Oxide from Diazeniumdiolates

Abstract

Aqueous photochemistry of diazen-1-ium-1,2,2-triolate (Angeli's anion) and (Z)-1[N-(3-aminopropyl)-N-(3-aminopropyl)amino]diazen-1-ium-1,2-diolate (DPTA NONOate) has been investigated by laser kinetic spectroscopy. In neutral aqueous solutions, a 266 nm photolysis of these diazeniumdiolates generates a unique spectrum of primary products including the ground state triplet ( 3 NO -) and singlet ( 1 HNO) nitroxyl species, and nitric oxide (NO · ). Formation of these spectrophotometrically invisible products is revealed and quantitatively assayed by analyzing a complex set of their cross-reactions leading to the formation of colored intermediates, the N 2 O 2 ·-radical and N 3 O 3 -anion. The experimental design employed takes advantage of the extremely slow spin-forbidden protic equilibration between 3 NO -and 1 HNO and the vast difference in their reactivity toward NO · . To account for the kinetic data, a novel combination reaction, 3 NO -+ 1 HNO, is introduced and its rate constant of 6.6 × 10 9 M -1 s -1 is measured by competition with the reduction of methylviologen by 3 NO -. The latter reaction occurring with 2.1 × 10 9 M -1 s -1 rate constant and leading to the stable, colored methylviologen radical cation is useful for detection of 3 NO -. The distributions of the primary photolysis products (Angeli's anion: 22% 3 NO -, 58% 1 HNO, and 20% NO · ; DPTA NONOate: 3% 3 NO -, 12% 1 HNO,and 85% NO · ) show that neither diazeniumdiolate is a highly selective photochemical generator of nitroxyl species or nitric oxide, although the selectivity of DPTA NONOate for NO · generation is clearly greater.

Reactivity of iron(II)-bound nitrosyl hydride (HNO, nitroxyl) in aqueous solution

“…− 0.44 V)[53], with complex (I), we found no reaction in the minute time scale. Instead, a very slow spontaneous decomposition of (I) evolved, with the same rate than that described in Section 3.2.…”

“…We report on the reactions with oxidants that have been previously assayed with free HNO: hexacyanoferrate(III) and methyl viologen [53]. The NP ion has been also selected as a potential oxidant, given the possible reaction between bound NO + and HNO, yielding the comproportionation product [Fe II (CN) 5 NO] 3- [52].…”

Complexes of some tervalent metals with N-alkyl(benzyl)nitrozohydroxylamine derivatives

“…The compounds containing nitrozohydroxylamine moieties are used as broadspectrum (vasodilative, sedative, analgesic, antitumor, antiviral, etc.) medicines [21][22][23][24][25][26][27][28]. The study of specific features in the spatial and electronic structures and properties of metal complexes with organic ligands containing N-nitrozohydroxylamine moieties can be useful for understanding the interaction between nitrogen monoxide and metal-containing moieties of biological molecules and, thereby, can make a certain contribution to studying the mechanism of its effect on living systems [29][30][31][32].…”

Detection of nitroxyl (HNO) by a prefluorescent probe

“…Possible reactions of HNO and associated rate constants. Reaction rate constants are from References and …”