A binuclear Cu(II) complex, 1, {Cu-2(L-)(2)(OAc)](OAc) of imidazole-based ligand LH {LH = 2-(bis(2-ethyl-5-methyl-1H-imidazol-4-yl)methyl)phenol} was synthesized and characterized spectroscopically and structurally. Addition of an equivalent amount of nitric oxide (NO) by a gastight syringe to the acetonitrile:methanol (5:1, v/v) solution of complex 1 at room temperature resulted in the reduction of Cu(II) center to Cu(I) with concomitant C-nitrosation of the ligand. Spectroscopic characterization of the resulting Cu(I) complex (la) of the C-nitrosylated ligand, L' {L' = 2-(bis(2-ethyl-S-methyl-1H-imidazol-4-yl))methyl)-4-nitroso-phenol} has been done. The Cu(I) complex, la, further reacted with NO to result in the corresponding N-nitrosohydroxylaminato complex, 2, [Cu-2(L-ONNO)(2)] (OAc)(2) through the formation of a Cu(I)-nitrosyl intermediate. A small fraction of the nitrosyl intermediate decomposed to the corresponding Cu(II) complex 3, [Cu(L')(2)], and N2O in a parallel reaction.