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Presentation
Formation and Characterization of Binuclear Copper Superoxide and Peroxynitrite Complexes.pdf
University of Pennsylvania, Mid-Atlantic Seaboard Inorganic Symposium (MASIS) 2016 (2016)
  • Rui Cao, Johns Hopkins University
Abstract
Oxygenation of [Cu2(UN-O–)(DMF)]2+ (1), a structurally characterized dicopper Robin-Day class I mixed-valent Cu(II)Cu(I) complex, with UN-O– as a binucleating ligand and where dimethylformamide (DMF) binds to the Cu(II) ion, leads to a superoxo-dicopper(II) species [CuII2(UN-O–)(O2•–)]2+ (2). Complex 2 can be reversibly reduced to the peroxide species [CuII2(UN-O–)(O22–)]+, using varying outer-sphere ferrocene or ferrocenium redox reagents. A Nernstian analysis could be performed by utilizing a mono-diphenylamine substituted ferrocenium salt to oxidize the peroxo complex, leading to an equilibrium mixture with Ket = 5.3 (–80 °C); a standard reduction potential for the superoxo-peroxo pair is calculated to be E° = + 130 mV vs SCE. The peroxide complex and the superoxide complex are characterized by rRaman spectroscopy, respectively. The superoxide complex 2 further reacts with excess nitric oxide gas to form a peroxynitrite complex [CuII2(UN-O–)(–O2NO)]2+ (3)which is characterized by low temperature electrospray ionization mass spectrometry (ESI-MS) and infrared spectroscopy (IR) with N-O stretching bands at 1520 cm-1 and 1640 cm-1 which are presumably due to the cis- and trans- conformer of the peroxynitrite complex 3. Additionally, the mixed-valent Cu(II)Cu(I) complex reacts directly with nitric oxide to form a copper nitrosyl complex which can be best described as a mixed valence [CuI,II(UN-O–)(NO)]2+ (4) species, based on the observed N-O stretching vibration at 1670 cm-1. This mixed valence copper nitrosyl complex 4 can generate the same peroxynitrite complex upon removing excess nitric oxide and adding excess dioxygen gas. The peroxynitrite complex 3 that is produced by either process shows full nitration in the presence of the substrate 2,4-di-t-butyl phenol on the ortho position. Warming up of the peroxynitrite complex 3 in CH2Cl2 as solvent, results in nitration on the para position of the phenol group of the ligand and a chloride bridged dicopper complex.
Publication Date
Fall 2016
Citation Information
Rui Cao. "Formation and Characterization of Binuclear Copper Superoxide and Peroxynitrite Complexes.pdf" University of Pennsylvania, Mid-Atlantic Seaboard Inorganic Symposium (MASIS) 2016 (2016)
Available at: http://works.bepress.com/rui-cao/3/