ESR studies of nitrogen-centered free radicals. 39. N1,N5-bis(arylthio)-2,4-diphenyl-1,3,5-triazapenta-1,3-dienyl radicals. An electron spin resonance study
作者:Yozo Miura、Akio Tanaka
DOI:10.1021/jo00012a032
日期:1991.6
A new class of nitrogen-centered free radicals, N1,N5-bis(arylthio)-2,4-diphenyl-1,3,5-triazapenta-1,3-dienyl radicals 1 have been generated by hydrogen atom abstraction from N1,N5-bis(arylthio)-2,4-diphenyl-1,3,5-triazapenta-1,3-dienes 2 or by photolysis of 2 or N1,N5,N5-tris(arylthio)-2,4-diphenyl-1,3,5-triazapenta-1,3-dienes 3 using a UV or xenon lamp. Radicals 1 persist in solution and can be isolated as a diamagnetic dimer which, in solution, dissociates in part into 1 at room temperature. The thermodynamic parameters for the 4 reversible 2(1) equilibrium are 87.5 kJ mol-1 (DELTA-H-degrees) and 153 J K-1 mol-1 (DELTA-S-degrees), respectively. Radicals 1 have afforded the ESR spectra that show a(N1) (and a(N5) 0.400-0.431, a(N3) 0.278-0.312, a33S 0.48, and a(H) (due to the protons of the arylthiyl groups) 0.022-0.076 mT. On the basis of these ESR results, it is concluded that in 1 the unpaired electron resides mainly on the three nitrogen and two sulfur atoms.