ESR Spectra of Radicals Obtained by the Addition of NH 2 · and of CH 2 OH · to Vinyl Compounds

Chemically Induced Dynamic Electron Spin Polarization-Detected Energy Transfer. Substrate Size Effects and Solvent Dependence

Time-resolved electron paramagnetic resonance spectroscopy is used to probe energy transfer from aromatic photoexcited triplet states to azo compounds in liquid solution. The observation of chemically induced dynamic electron spin polarization in the spectra gives precise information regarding the spin physics and mechanism of the energy transfer process. The substrate size is varied by altering the chain length of alkyl chains covalently attached to the azo compounds via ester or amide linkages. The solvent dependence of the energy transfer process is also investigated. The results are discussed in terms of Dexter and Förster mechanisms for energy transfer, the properties of the excited states, and the diffusive properties of the molecules in the solvents of interest. Decomposition rate studies and fluorescence measurements are also reported.

Metal-catalyzed anaerobic disproportionation of hydroxylamine. Role of diazene and nitroxyl intermediates in the formation of N2, N2O, NO+, and NH3

The catalytic disproportionation of NH(2)OH has been studied in anaerobic aqueous solution, pH 6-9.3, at 25.0 degrees C, with Na(3)[Fe(CN)(5)NH(3)].3H(2)O as a precursor of the catalyst, [Fe(II)(CN)(5)H(2)O](3)(-). The oxidation products are N(2), N(2)O, and NO(+) (bound in the nitroprusside ion, NP), and NH(3) is the reduction product. The yields of N(2)/N(2)O increase with pH and with the concentration of NH(2)OH. Fast regime conditions involve a chain process initiated by the NH(2) radical, generated upon coordination of NH(2)OH to [Fe(II)(CN)(5)H(2)O](3)(-). NH(3) and nitroxyl, HNO, are formed in this fast process, and HNO leads to the production of N(2), N(2)O, and NP. An intermediate absorbing at 440 nm is always observed, whose formation and decay depend on the medium conditions. It was identified by UV-vis, RR, and (15)NMR spectroscopies as the diazene-bound [Fe(II)(CN)(5)N(2)H(2)](3)(-) ion and is formed in a competitive process with the radical path, still under the fast regime. At high pH's or NH(2)OH concentrations, an inhibited regime is reached, with slow production of only N(2) and NH(3). The stable red diazene-bridged [(NC)(5)FeHN=NHFe(CN)(5)](6)(-) ion is formed at an advanced degree of NH(2)OH consumption.

ESR investigation of gamma irradiated sulbactam sodium

In the present work, radiolysis of gamma irradiated sulbactam sodium (SS) was investigated through detailed ESR studies performed at low and at high temperatures on the radiolytic products induced in this drug after gamma irradiation in the dose range of 3-15 kGy. While unirradiated SS presented no ESR signal, irradiated SS exhibited an ESR spectrum with many resonance peaks. Variations of the spectrum pattern and of the intensities of resonance peaks with microwave power, applied radiation dose, storage time and temperature were followed. A radical with unpaired electron localised on the carbon atom of five membered ring directly attached to two CH(3) groups and SO(2)(-) ionic radical called as species A and B, respectively, were found to be produced after gamma radiolysis of SS. The characteristic spectral and kinetic features of these species were determined by spectrum simulation calculation and by curve fitting techniques using experimental signal intensity data as input. Although, species A was fairly unstable at room and especially at high temperatures, species B were observed to be relatively stable even at high temperatures having activation energies of E(A) (+/-4)kJ/mol and E(B) (+/-3)kJ/mol, respectively, at room temperature. Four different mathematical functions were tried to explore the dosimetric features of SS and a linear function of applied dose described best the dose-response data obtained for stable species, that is, radical B, in the dose range of 0-10 kGy. An accuracy of 4% in the dose measurements was concluded to be achievable through back-projection dose calculations if SS were used as a dosimetric material.