The Origin of Bulk Polarity in Hydrogensulfate Salts

Abstract

The crystal packing motifs exhibited by hydrogensulfate salts, including 10 new organic cation salts, are analyzed in the context of understanding the criteria that control bulk polarity in the absence of chiral moieties. Fortyfive hydrogensulfate salts were analyzed, 27 crystallize via head-to-tail strand motifs that are conducive to the presence of bulk polarity, 16 crystallize via packing of dimer motifs and 2 exhibit cocrystallization of both strand and dimer motifs. The majority of the strand motifs randomly aggregate via one of the expected crystallographic operations: translation, glide or screw. However, only 8 compounds crystallize in non-centrosymmetric space groups. The most desirable aggregate from the perspective of maximizing bulk polarity, the translation aggregate, was observed in 9 compounds. We discuss our observations in the broader context with particular emphasis on the development of strategies for crystal engineering of polar solids.