@article { ISI:000404882900021,
	title = {High Z{\textquoteright} structures of 1,2,3,5-dithiadiazolyls and of 1,2,3,5-diselenadiazolyls containing the first structurally characterized monomeric diselenadiazolyls},
	journal = {CRYSTENGCOMM},
	volume = {19},
	number = {26},
	year = {2017},
	month = {JUL 4},
	pages = {3698-3707},
	abstract = {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 P (1) over bar 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 fourfold 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 alpha form crystallizes in P (1) over bar with Z = 6 and the beta in P2(1)/c with Z = 20. The a 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 beta polymorph consists of clusters of four cis-oid dimers that link into chains along the b axis, whereas the fifth molecule links via -C equivalent to N center dot center dot center dot 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 1,2,3,5-diselenadiazolyl crystal structures reveals an extraordinarily large number of structures with Z{\textquoteright} \&gt; 1 (72\%) and also those with Z{\textquoteright} \&gt;= 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.},
	issn = {1466-8033},
	doi = {10.1039/c7ce00863e},
	author = {Boer{\'e}, R. T. and Hill, Nathan D. D.}
}
