ESR Studies of Nitrogen-centered Free Radicals,<i>N</i>-Aryl-<i>N</i>-phenylthioaminyls
作者:Yozo Miura、Masayoshi Kinoshita
DOI:10.1246/bcsj.50.1142
日期:1977.5
generated by the photolysis of benzenesulfenanilides (1) in benzene in the presence of di-t-butyl peroxide or by the oxidation of 1 in benzene with lead dioxide. The ESR spectra of the radicals were completely analyzed by labeling some radicals with deuterium and with the aid of a computer simulation technique. The unpaired electron is distributed mainly on the nitrogen atom and the N-phenyl ring. The values
各种取代的 N-苯基-N-苯硫胺基 (2), Ar-\dotN-S-Ar', 是在二叔丁基过氧化物存在下通过苯亚磺酰苯胺 (1) 在苯中的光解产生的。用二氧化铅在苯中氧化 1。通过用氘标记一些自由基并借助计算机模拟技术,对自由基的ESR光谱进行了完整的分析。未成对电子主要分布在氮原子和N-苯环上。将 aN 的值与哈米特方程中的 σ 或 σ− 作图,发现根据沃尔特标准,2 属于 S 类。
Generation, Isolation, and Characterization of N-(Arylthio)-7-tert-butyl- and N-(Arylthio)-2,7-di-tert-butyl-1-pyrenylaminyl Radicals
N-(Arylthio)-7-tert-butyl-1-pyrenylaminyl (2) and N-[(4-nitrophenyl)thio]-2,7-di-tert-butyl-1-pyrenylaminyl radicals (3) are prepared by PbO2 oxidation of N-(arylthio)-7-tert-butyl-1-aminopyrenes and N-[(4-nitrophenyl)thio] -2,7-di-tert-butyl-1-aminopyrene, respectively, and studied by ESR and ENDOR spectroscopy. The kinetic ESR study shows that, while aminyls 2 gradually decompose in solution at room temperature, aminyl 3 is quite persistent, even in refluxing benzene, and shows no tendency to dimerize, even at low temperatures. These interesting properties of 3 permit us to isolate 3 as radical crystals in 28-31% yield. The hyperfine splitting (hfs) constants of 2 and 3, determined by ESR and ENDOR spectroscopic methods, show an extensive delocalization of the unpaired electron onto the pyrene ring. Comparison of the hfs constants of 2 and 3 shows that a more extensive delocalization of the spin into the pyrene ring takes place in 3. This is accounted for in terms of the difference in the conformations of 2 and 3.