Peroxynitrite chemistry derived from nitric oxide reaction with a Cu(ii)–OOH species and a copper mediated NO reductive coupling reaction

Abstract

New peroxynitrite-copper chemistry ensues via addition of nitric oxide (•NO(g)) to a CuII-hydroperoxo species. In characterizing the system, the ligand-Cu(I) complex was shown to effect •NO(g) reductive coupling, a new reaction type. Biological implications are discussed.

A Peroxynitrite Dicopper Complex: Formation via Cu–NO and Cu–O2 Intermediates and Reactivity via O–O Cleavage Chemistry

“…Beckman 2b,c,g and Koppeno 2c have discussed this in particular for the interaction of PN with the enzyme CuZn-superoxide dismutase or Fe III -EDTA (or other) coordination complexes and postulate that metal ions favor heterolytic cleavage of the PN O−O bond to give nitronium ion (NO 2 + ), which is a powerful nitrating agent. More recently, Girault 12f has shown that copper ion complexes may mediate PN formation and then phenol nitration. Metal-bound PN complexes have now been shown by other groups 12a,c,e,f,41 to react with substituted phenols, in particular 2,4-di- tert -butylphenol (DTBP) as an analytically useful substrate.…”

“…More recently, Girault 12f has shown that copper ion complexes may mediate PN formation and then phenol nitration. Metal-bound PN complexes have now been shown by other groups 12a,c,e,f,41 to react with substituted phenols, in particular 2,4-di- tert -butylphenol (DTBP) as an analytically useful substrate.…”

“…Following the now known M−O 2(g) + NO (g) biological and chemical examples to give PN and subsequent reactions, plus the likely importance of copper in chemical or biological systems, 1c,6,7,9,12f we report here on a new system involving binuclear copper species, which gives rise to chemistry not previously observed, providing new insights. In the past, we performed extensive studies concerning the binucleating ligand UN-O−, 29 where a phenolate O-atom bridges two copper ions.…”

“…8c,10 A recent computational study shows that Aβ bound to Cu 2+ ion could generate PN in the presence of ascorbate, nitric oxide, and dioxygen. 11 In fact, this proposal has separate experimental backing, in that ligand–copper complexes have in the past few years been shown to be able to form LCu( − OON═O) species, 12 with reactions of Cu I with O 2(g) 12a and then NO (g) or Cu 1 –NO with O 2(g) (Scheme 1). 12b–e …”

“…For two cases involving copper–peroxynitrite complexes, 12a,b LCu II −PN complexes thermally transform to give LCu II −nitrite products plus dioxygen. This seems to also correspond to known aqueous chemistry: peroxynitrite decomposes through various pathways, 3c,21 , including its degradation according to 2 − OON═O → O 2 + 2NO 2 − under basic conditions and relatively high concentration,s 21b,d,e and such reactivity has even been observed in aqueous chemistry with copper ion.…”