75877-78-0Relevant academic research and scientific papers
Formation and Identification of Aryldiazenyl Radicals Using the ESR Technique
Suehiro, Tadashi,Masuda, Seiichi,Tashiro, Takaaki,Nakausa, Ryuichi,Taguchi, Masamichi,et al.
, p. 1877 - 1886 (2007/10/02)
Aryldiazenyl radicals were formed at -104 - -116 deg C by photoirradiation of cyclopropane solutions of 1-aryl-2-(arylthio)diazenes and of 1-aryl-3,3-dimethyltriazenes in the presence or absence of olefins, and also by irradiation of cyclopropane solutions of substituted 1,2,3-benzothiadiazoles in the presence of di-t-butyl peroxide.The ESR spectra were analyzed and the hfs constants were assigned by reference to the spectra of methyl, 2H, and 15N-labelled aryldiazenyl radicals and to the results of CINDO calculations.Aryldiazenyl radicals are relatively persistent and the -N=N group rotates about the C-N2 bond axis.The preferred conformations of the radicals were considered.
Solvent Effects in the Photoinduced Electron Transfer Reaction of Uncharged Donors with Arenediazonium Salts
Becker, H. G. O.,Israel, G.
, p. 411 - 421 (2007/10/02)
In the photochemical electron transfer reactions to arene diazonium salts no strong Coulomb forces arise but the rate constants possibly vary in dependence on the state of the diazonium salt (tight ion pair in nonpolar solvents or free diazonium cations).This problem is studied in the present work using anthracene and tetracene, respectively, as electron donors.They react in their S1 states diffusion-controlled with ion pairs ArN2(1+)*BF4(1-), whereas the respective triplet reactions proceed up to 1E3 times more slowly.These rates are not significantly influenced by the dielectric properties of the solvent.Thus, ion pairing of the diazonium salts in solvents of low polarity has no screening effect on the electron transfer.This behavior is explained including electrostatic effects into the MARCUS theory of outer sphere electron transfer processes.No indication of a Marcus inverted region was found.
Photochemical Dediazoniation of Arene Diazonium Salts Catalyzed by Quinones
Becker, H. G. O.,Jirkovsky, J.,Fojtik, A.,Kleinschmidt, J.
, p. 505 - 511 (2007/10/02)
The rate constants of the hydrogen abstraction of triplet-excited p-benzoquinone (BQ), duroquinone (DQ), p-chlorophenyl-p-benzoquinone (PQ) and 2,5-di(p-chlorophenyl)-p-benzoquinone (P2Q) from n-heptane and acetonitrile are determined by laser flash photolysis as well as the rate constants for the reactions with oxygen. The semiquinones formed are in equilibrium with their respective semiquinone anions; at pH 3 and pH 7, respectively, it was possible in acetonitrile/water solution to determine separately the rate constants for their disproportionation affording quinones and hydroquinones and the rate constants for electron transfer to p-chlorbenzene diazonium tetrafluoroborate.It comes out that the electron transfer to the diazonium compound only competes favorably with the disproportionation in the case of the semiquinone anions.
Pulse Radiolysis of Arenediazonium Salts in Water/tert.-Butanol
Brede, O.,Mehnert, R.,Naumann, W.,Becker, H. G. O.
, p. 666 - 672 (2007/10/02)
The pulse radiolysis of benzenediazonium tetrafluoroborate and its p-NMe2, p-MeO, p-Me, p-Cl, p-COOEt, and p-CN derivatives was studied in water/tert.-butanol mixtures.Absorption spectra observed at wavelengths between 400 and 700 nm were attributed to the recombination products (tetrazadienes) Ar-N=N-N=N-Ar of arenediazo radicals Ar-N=N. which are generated by a diffusion-controlled reaction of the solvated electrons with the solute.The recombination of Ar-N=N. competes with an unimolecular decay of these radicals.According to an inhomogeneous initial distribution of Ar-N=N. the apparent rate of the recombination reaction is higher than the diffusion-controlled limit.For the unimolecular decay of Ar-N=N. rate constants between (1.8 and 330) * 105s-1 were calculated.The tetrazadienes decompose unimolecularly with rate constants from (0.3 to 17) * 105s-1. - The rate constants of the decay of the arenediazo radicals as well as of the decomposition of tetrazadienes exhibit good Hammet plots with almost identical reaction constants indicating similar paths of nitrogen elimination.
