Hydrogen and chalcogen bonds in crystals of chalcogenadiazolecarboxylic acids – competition or cooperation?

Abstract

This article presents crystal structures of chalcogenadiazolecarboxylic acids bearing both a hydrogen and a chalcogen bond donor. The selected molecules varied in the size of the aromatic unit, the chalcogen atom and/or the position of the carboxyl group in the core structure. The most common synthons in their lattice are R²₂(8) self-complementary acid dimers or four-membered [Ch⋯N]₂ rings. Supramolecular synthons where chalcogenadiazole moieties interact with the carboxyl group were also identified. Both ESP calculations and experimental data showed that all the studied molecules adopted flat conformations, but only in the case of three crystal structures were flat sheets observed. To assess the contribution of hydrogen and chalcogen bonds to the stabilization of the crystal structure, crystal lattice energy calculations were performed.