ESR spectroscopy of the 4,5‐bis(methoxycarbonyl)‐1,3,2‐dithiazol‐2‐yl radical labelled with sulphur‐33 and nitrogen‐15

A derivative of the 1,3,2‐dithiazol‐2‐yl radical was labelled with 33S in order to evaluate the p spin densities on the sulphur atoms. This information is required to provide a full description of the SOMO which, in turn, aids the understanding of the structure of the radical dimers. An unexpected result is that the two sulphur atoms are non‐equivalent in the solid state. Calculations suggest that this is due to out‐of‐plane twisting of the substituent groups. Comparison of the ESR parameters of the bis(methoxycarbonyl) derivative with other members of the 1,3,2‐dithiazol‐2‐yl group of radicals (including the parent radical) shows that it is a good model for the whole group.