Robust S₄⋅⋅⋅O Supramolecular Synthons: Structures of Radical‐Radical Cocrystals [p‐XC₆F₄CNSSN]₂[TEMPO] (X=F, Cl, Br, I, CN)

Abstract

Cocrystallization of the dithiadiazolyl (DTDA) radicals p-XC 6 F 4 CNSSN (X=F, Cl, Br, I, CN) with TEMPO afforded the 2 : 1 cocrystals [p-XC 6 F 4 CNSSN] 2 [TEMPO] (1-5) whose structures all reflect a common S 4 •••O supramolecular motif.The nature of this interaction was probed by DFT calculations (M06/aug-cc-pVDZ) on 1 which revealed that the enthalpy of formation of the [C 6 F 5 CNSSN] 2 [TEMPO] supramolecular motif from [C 6 F 5 CNSSN] 2 and TEMPO is substantial (À 54.0 kJ mol À 1 ). Electronic structure calculations revealed a TEMPO-based doublet S = 1 = 2 configuration as the ground state with limited spin density on the DTDA rings (2.4 %). The corresponding spin quartet state is + 78.9 kJ mol À 1 higher in energy. An atoms-in-molecules analysis reveals four bond critical points (BCPs) between the TEMPO O and the DTDA S atoms as well as additional BCPs between selected DTDA S atoms and methyl H atoms of the TEMPO molecule. Herein, the structures of 2-5 are considered within the context of a hierarchical view of competing and complementary intermolecular interactions; in particular, the established supramolecular CN•••SÀ S synthon is sacrificed in order to form the new S 4 •••O interaction.

Towards molecular alloys: computational and experimental studies on (p-NCC6F4CNSeSeN)x(p-NCC6F4CNSSN)1−x

“…In the field of organic magnetism, multi-component systems have largely focussed on the development of radical cocrystals as a route towards organic ferrimagnets, 20–23 although a few limited examples of molecular alloys of radicals have been reported (Chart 1). 17,24 A common theme of these alloys is the similarity in molecular structure, though it is notable that the two components need not be isomorphous and there is no reason for the major component in the alloy to dictate the crystal morphology.…”

Dispersion in Crystal Structures of 1-Chloro-3-aryl-5-trihalomethyl-1λ4,2,4,6-thiatriazines: Towards an Understanding of the Supramolecular Organization of Covalent Thiazyl Chlorides

“…1,2,15 A number of approaches have been used to rationalize the observed { + S•••N − } 2 interactions, ranging from simple geometric parameters (distances, angles, interplanar separations), 7,11,16 electrostatic interactions using molecular electrostatic potentials (MEP), 9,10 and formal computation of -holes. [2][3][4][5]7,8…”

“…[1][2][3][4][5][6][7][8][9][10][11][12] A very common motif in all thiazyl intermolecular contacts is an approximately parallelepiped 'double S•••N' interaction (Figure 1, A-C). 13 This motif, which will be designated here as { + S•••N − } 2 , has re-ceived special attention in thiazyl radicals and triplet diradicals, many of which also form 'pancake bonded' dimers, as commonly but not exclusively observed for 1,2,3,5-dithiadiazolyls, A, [3][4][5][6][7][8][9][10][11] and for all known exemplars of 1,3,2,4,6-dithiatriazines, B. 14 For these, the { + S•••N − } 2 motifs usually further link dimers in an out-of-register fashion, as shown in Figure 1.…”

“…There is a strong current interest in supramolecular interactions between heterocyclic thiazyls (i.e., compounds containing unsaturated S-N bonds) and their heavier chalcogen (Se,Te) analogues. [1][2][3][4][5][6][7][8][9][10][11][12] A very common motif in all thiazyl intermolecular contacts is an approximately parallelepiped 'double S•••N' interaction (Figure 1, A-C). 13 This motif, which will be designated here as { + S•••N − } 2 , has re-ceived special attention in thiazyl radicals and triplet diradicals, many of which also form 'pancake bonded' dimers, as commonly but not exclusively observed for 1,2,3,5-dithiadiazolyls, A, [3][4][5][6][7][8][9][10][11] and for all known exemplars of 1,3,2,4,6-dithiatriazines, B.…”

“…1,2,15 A number of approaches have been used to rationalize the observed { + S•••N − } 2 interactions, ranging from simple geometric parameters (distances, angles, interplanar separations), 7,11,16 electrostatic interactions using molecular electrostatic potentials (MEP), 9,10 and formal computation of -holes. [2][3][4][5]7,8 By contrast, very little interest has been shown in the supramolecular structures of thiazyl halides, even though especially the chlorides are by far the most common precursors to many of the above-mentioned neutral thiazyls. 17 This may, in part, be a consequence of the very finely tuned balance between charge-separated (thiazyl) + Cl − , such as D, and the covalent thiazyl chlorides, such as E. 17 The origins of the choice between these rather drastic structure alternatives is poorly understood.…”