A single-crystal electron spin resonance study of the cyclic 1,2,4,3,5-trithiadiazolyl radical, S3N2+•

An anisotropic ESR signal detected in single crystals of 5-methyl-1,3,2,4-dithiazolylium hexafluoroarsenate [Formula: see text] is shown to be that of 1,2,4,3,5-trithiadiazolyl, S3N2+•. The g- and 14N-hyperfine tensors for this radical were established in the monoclinic abc* crystal-axis system from spectral measurements at room temperature on aligned single crystals. Agreement of the principal values of the tensors with those obtained in our earlier studies by simulation of powder spectra is excellent. The g-tensor (2.0021, 2.0072, 2.0248) and the two 14N-tensors (25.4, 0.8, 0.8 MHz) are collinear within experimental error and lie with minimum g and maximum hyperfine perpendicular to the plane of the host cation. The electronic structure of the radical deduced from our earlier studies (2A2 in C2V) is confirmed, and the impurity is shown to substitute for the host cation in the anticipated manner.