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Abstract
The EPR spectra of six 1,2,4,6-thiatriazinyls have been redetermined and simulated using modern computer simulation programs. The hyperfine coupling (hfc) constants determined from the simulations differ in some cases significantly from those reported previously. The presence of unresolved coupling also can be detected in some of the spectra. The hfc values to the two kinds of nitrogen atoms in the ring vary in a systematic fashion with the relative electron-withdrawing character of the substituents attached to the ring carbon atoms at the 3 and 5 positions.
This work was supported by the Natural Sciences and Engineering Research Council of Canada and the University of Lethbridge Research Fund (R.T.B.). The EPR spectrometer was purchased with an NSERC Equipment Grant awarded to the University of Calgary. We thank that institution for generous access to the instrument. The University of Lethbridge Travel Fund assisted with travel expenses related to the delivery of the oral version of this paper.
Notes
a Hyperfine coupling constants and linewidths expressed in units of milliTesla (mT).
b Expressed as the % Lorentzian character; balance is Gaussian. Lorentzian lineshape is expected where relaxation effects dominate, whereas Gaussian lineshape is associated with unresolved hfc.
