ESR spectroscopy of some dicyano-, pyrazino- and quinoxalino-1,3,2-dithiazolyl radicals
作者:Yuen-Li Chung、Shirley A. Fairhurst、Duncan G. Gillies、Gregor Kraft、Angelika M. L. Krebber、Keith F. Preston、Leslie H. Sutcliffe、Gotthelf Wolmershäuser
DOI:10.1002/mrc.1260300814
日期:1992.8
Several symmetrical 1,3,2-dithiazol-2-yl radicals have been examined that have in common nitrogen-containing substituents at the 4- and 5-positions, namely 4,5-dicyano-1,3,2-dithiazol-2-yl, [15N2]-1,3,2-dithiazolo [4,5-b] pyrazin-2-yl and 1,3,2-dithiazoleo [4,5-b] quinoxalin-2-yl. The ESR spectrum of the 4,5-dicyano radical does not reveal any 14N splittings from the cyanide groups; however, the pyrazine and the quinoxaline derivatives do have multi-lined well resolved spectra arising from substantial hyperfine interactions with these nuclei. The interactions are sufficiently large to be observed in the powder spectra of the latter. The presence of proton hyperfine interactions shows that unpaired-electron spin density is delocalized over all the rings. It has been found that the radicals attached to pyrazine and quinoxaline can be incorporated into single crystals of naphthalene and phenazine, respectively.
我们研究了几种对称的 1,3,2-二噻唑-2-基,它们在 4 和 5 位上都有含氮取代基,即 4,5-二氰基-1,3,2-二噻唑-2-基、[15N2]-1,3,2-二噻唑并 [4,5-b] 吡嗪-2-基和 1,3,2-二噻唑并 [4,5-b] 喹喔啉-2-基。4,5-二氰基的 ESR 光谱没有显示任何来自氰基的 14N 分裂;然而,吡嗪和喹喔啉衍生物确实具有多线分辨良好的光谱,这是因为与这些原子核之间存在大量超精细相互作用。在后者的粉末光谱中可以观察到足够大的相互作用。质子超正弦相互作用的存在表明,非配对电子自旋密度在所有环上都是分散的。研究发现,附着在吡嗪和喹喔啉上的自由基可以分别掺入萘和吩嗪的单晶体中。