On the Design of Radical-Radical Cocrystals

Formation of radical-radical cocrystals is an important step towards the design of organic ferrimagnets. We describe a simple approach to generate radical-radical cocrystals through the identification and implementation of well-defined supramolecular synthons which favor cocrystallization over phase separation. In the current paper we implement the structure-directing interactions of the E-E bond (E=S, Se) of dithiadiazolyl (DTDA) and diselenadiazolyl (DSDA) radicals to form close contacts to electronegative groups. This is exemplified through the preparation and structural characterization of three sets of radical cocrystals; the 2:2 cocrystal [PhCNSSN]₂ [MBDTA]₂ (4) [MBDTA=methyl benzodithiazolyl] and the 2:1 cocrystals [C₆ F₅ CNEEN]₂ [TEMPO] (E=S, 5; E=Se, 6). In 4 the two types of radical are linked via bifurcated inter-dimer ^δ+ S⋅⋅⋅N^δ- interactions whereas 5 and 6 exhibit a set of five-centre ^δ+ E⋅⋅⋅O^δ- contacts (E=S, Se).