Reaction of a Copper(II)–Nitrosyl Complex with Hydrogen Peroxide: Phenol Ring Nitration through a Putative Peroxynitrite Intermediate

Copper­(II)
complex, 1, with the histidine-derived ligand L (L = methyl 2-(2-hydroxybenzylamino)-3-(1H-imidazol-5-yl)­propanoate) has been synthesized and characterized.
Single-crystal structure determination reveals a diphenolato-bridged
dicopper­(II) core in 1. Addition of •NO to an acetonitrile solution of 1 affords the corresponding
mononuclear copper­(II)–nitrosyl complex, 2. In
the presence of H2O2, 2 results
in formation of the corresponding copper­(I)–peroxynitrite.
Formation of peroxynitrite (−OONO) intermediate
is evident from its characteristic phenol ring nitration reaction
which resembles the tyrosine nitration in biological systems. Further,
isolation of nitrate (NO3–) as the decomposition
product from 2 at room temperature also supports the
involvement of –OONO intermediate.