167758-93-2Relevant academic research and scientific papers
An EPR and MS Investigation of Hexa-Substituted Pyrrolidine-1-oxyl Aminoxyl Stable Radicals. Unexpectedly Large γ-Hydrogen Splittings
Zhang, Yong-Kang,Janzen, Edward G.
, p. 1531 - 1536 (2007/10/03)
The γ-hydrogen hyperfine splitting constant (γ-H hfsc) for stable aminoxyl (nitroxide) spin labels such as 2,2,5,5-tetramethylpyrrolidine-1-oxyl and their derivatives is usually very small (/=2.0 G) have been detected with EPR for the first time from ten 2-alkyl-2-phenyl-3,3,5,5-tetramethylpyrrolidine-1-oxyl stable aminoxyl radicals.It is discovered that γ-H hfsc's are very sensitive to the size and the substitution pattern of 2-alkyl groups.When the 2-alkyl group is CH3 or CD3, γ-H hfsc is very large, equal to 4.72 G in C6H6.If the substituent is longer than C2H5, such as n-C3H7, n-C4H9, n-C5H11, n-C6H13 and CH2=CHCH2- substituents, the γ-H hfsc is slightly smaller, equal to 4.59 G.For secondary substituents such as sec-C4H9 and cyclo-C6H11, the γ-H hfsc decreases to 2.00 G.Intermediate γ-H hfsc's correspond to C6H5CH2 (3.18 G) or a teriary alkyl group such as t-C4H9 (3.47 G).Variation of γ-H hfsc's is based on the change of the pyrrolidine ring conformation which is a result of the 2-alkyl group influence.The structures of these aminoxyl radicals are characterized also with mass spectrometry.Possible MS fragmentation mechanisms are discussed. - Keywords: EPR Spin Trapping, Aminoxyl Radical, Spin Adduct, 2-Alkyl-2-phenyl-3,3,5,5-tetramethylpyrrolidine-1-oxyl
