Physical Properties of 1,3,2,4-Dithiadiazolyls

Since such dithiadiazolyls may be either radical (3 ) or spin-paired species (3), these two types show significant differences in their physical properties. With the exception of (NC)2.C=CNSNS, which is purple-black, the latter are lightly colored and tend to be moderately stable to hydrolysis. In contrast, the esr-active radicals 3- tend to be light-, heat-, and moisture-sensitive. 

Many 1,3,2,4-dithiadiazolyl radicals have been detected by solution esr spectroscopy. In accordance with MO calculations (Section XIII), these radicals show coupling to one nitrogen nucleus N (farthest from the heterocyclic carbon) leading to a 1 1 1 triplet. Coupling to the second 

Isotropic ESR Data for 1, 3,2,4-Dithiadiazolyls (Coupling Constants in Milli-Teslas) 

Heterocyclic coupling constants refer to the following atom labeling scheme  

Owing to the thermal and photochemical sensitivity of the radicals (Section XXI.A) and, in some cases, the possibility of polymerization at high concentration (Section XXI.B), the data on pure samples are limited. The only magnetic data currently available for 1,3,2,4-dithiadiazolyl radicals are for 3 (R = rBu) at room temperature this compound is a brown liquid, with an effective magnetic moment of 1.5 p,B (87CC69), somewhat less than the anticipated value for a single unpaired electron of 1.73 fiB. Nevertheless, this material can be described as a paramagnetic liquid as it is virtually dissociated in the liquid state (see also Section IX.D). 

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