A. Heise, a Frank H. Köhler, B. Mota
Oct 1, 1999
Citations
1
Influential Citations
57
Citations
Journal
Journal of the American Chemical Society
Abstract
Nitronylnitroxide radicals substituted by 2‘-hydroxy-, 3‘-hydroxy-, 4‘-hydroxy-, and 4‘-methoxyphenyl groups and by a methyl group (2, 3, 4, 5, and 6, respectively) have been investigated in the solid state with 1H, 2H, and 13C NMR spectroscopy under magic angle spinning (MAS) and in solution with 1H and 2H NMR spectroscopy. Well-resolved 13C MAS NMR spectra have been recorded which show signals in ranges up to almost 1900 ppm. The 1H NMR signal spread does not exceed 60 ppm (except for a unique methyl signal of 6 near −230 ppm), and the resolution is worse than that of 13C NMR spectra. Narrower signals have been obtained with 2H NMR spectroscopy. The signals have been assigned with the help of various criteria including the results of ab initio calculations. From the NMR data it has been concluded that the nitronylnitroxide five-ring is puckered, thus rendering all substituents inequivalent. Signal coalescence at elevated temperatures has shown that these inequivalencies are partly averaged out while the...