Rotational correlation times and radii of dithiazol-2-yl and dithiazolidin-2-yl free radicals

Abstract

1,3,2-Dithiazol-2-yl and 1,3,2-dithiazolidin-2-yl radicals have been shown to be useful model compounds for detailed e.s.r. studies of rotational reorientation in liquid and frozen media. Consequently they are also potentially useful spin probes and spin labels. The e.s.r. powder spectra have been analysed and the resulting g and A tensors were used to calculate rotational diffusion correslation times, rotational energetics of activation and effective radii. The latter are a closer match to radii calculated from geometric radii than has been found for model nitroxy radicals: the energetics of activation for rotational diffusion indicate that the non-polar character of our radicals minimises solute–solvent interactions.