High Z’ structures of 1,2,3,5-dithiadiazolyls and of 1,2,3,5-diselenadiazolyls containing the first structurally characterized monomeric diselenadiazolyls
Boeré, René T.
Hill, Nathan D. D.
Royal Society of Chemistry
Crystals of 4-[3-(trifluoromethyl)phenyl]-3H-1,2,3,5-dithiadiazol-3-yl grown by slow sublimation in a three-zone furnace form in P1 ̅ with Z = 12. The six independent molecules combine into two cis-oid and one twisted dimer, which arrange in a layer structure as two elegant clusters, with non-crystallographic four-fold and two-fold symmetry, respectively. Crystals of 4-(3-cyano-5-tertbutyl-phenyl)-3H-1,2,3,5-diselenadiazol-3-yl, formed from decomposition of a bis-diselenadiazolyl, grow in two forms under different sublimation conditions using the same furnace. The α form crystallizes in P1 ̅ with Z = 6 and the β in P21/c with Z = 20. The α polymorph consists of a distorted cis-oid dimer linked electrostatically to a monomer in the asymmetric unit. These cluster with a second unit to a centrosymmetric aggregate of six heterocycles. The β polymorph consists of clusters of four cis-oid dimers that link into chains along the b axis, whereas the fifth molecule links via -C≡N∙∙∙Se supramolecular synthons into an infinite chain of monomers also along the b axis but out-of-register with the dimer chain. A carefully curated compilation of all 83 distinct 1,2,3,5-dithiadiazolyl and of all 24 distinct 1,2,3,5diselenadiazolyl crystal structures reveals an extraordinarily large number of structures with Z' > 1 (72%) and also those with Z' ≥ 3 (24%), compared to the average for organic molecules over the whole collection in the Cambridge Structure Database. This high incidence is analyzed and attributed to competing intermolecular synthons.
Sherpa Romeo yellow journal. Permission to archive accepted author manuscript
Dithiadiazolyl , Diselenadiazolyl , Radical dimer , High Z' , Monomeric free radicals , Sublimation , Crystallography
Boeré, R. T., & Hill, N. D. D. (2017). High Z’ structures of 1,2,3,5-dithiadiazolyls and of 1,2,3,5-diselenadiazolyls. CrystEngComm, 19, 3698-3707. https://doi.org/10.1039/C7CE00863E