One-electron reduction of arenediazonium compounds by physiological electron donors generates aryl radicals. An EPR and spin trapping investigation.
Arenediazonium compounds (ArN2+) are strong oxidizing agents, which upon one-electron reduction decompose, releasing aryl radicals (Ar.). The present studies were undertaken to determine whether reductive fragmentation of ArN2+ can be induced by biologically relevant electron donors. We found that 4-X-Ph-N2+ (where X: -NO2, -Br, -Cl, -OMe and -N(Et)2) decomposes to the respective aryl radicals when reduced by ascorbate, NADH, potassium ferrocyanide, catechol or p-hydroquinone in aqueous solutions. Radical identification was based on analysis of the EPR spectra of spin adducts formed by reaction of these radicals with spin traps 2-methyl-2-nitrosopropane (MNP), 3,5-dibromo-4-nitrosobenzene sulphonate (DBNBS) or 5,5-dimethyl-1-pyrroline N-oxide (DMPO). This study shows that reduction of arenediazonium ions can be a convenient method for generating aryl radicals in aqueous solutions. In addition, this investigation confirms that biological reducing agents are capable of inducing fragmentation of ArN2+ into aryl radicals. This reaction may be pertinent to some biological actions of arenediazonium compounds.
Reszka
K J
KJ
Laboratory of Molecular Biophysics, National Institute of Environmental Health Sciences, National Institute of Health, Research Triangle Park, NC 27709, USA.
Chignell
C F
CF
D001205:Ascorbic Acid / Q000737:chemistry; D003979:Diazonium Compounds / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D009603:Nitroso Compounds / Q000737:chemistry; D016877:Oxidants / Q000737:chemistry*; D010084:Oxidation-Reduction; D013113:Spin Labels
D003979:Diazonium Compounds; D005609:Free Radicals; D009603:Nitroso Compounds; D016877:Oxidants; D013113:Spin Labels; C034526:tert-nitrosobutane; D001205:Ascorbic Acid