Cocrystals of 1,4-diethynylbenzene with 1,3-diacetylbenzene and benzene-1,4-dicarbaldehyde exhibiting strong nonconventional alkyne-carbonyl C-H...O hydrogen bonds between the components.

Abstract

Weak interactions between organic molecules are important in solid-state structures where the sum of the weaker interactions support the overall three-dimensional crystal structure. The sp-C-H...N hydrogen-bonding interaction is strong enough to promote the deliberate cocrystallization of a series of diynes with a series of dipyridines. It is also possible that a similar series of cocrystals could be formed between molecules containing a terminal alkyne and molecules which contain carbonyl O atoms as the potential hydrogen-bond acceptor. I now report the crystal structure of two cocrystals that support this hypothesis. The 1:1 cocrystal of 1,4-diethynylbenzene with 1,3-diacetylbenzene, C10H6·C10H10O2, (1), and the 1:1 cocrystal of 1,4-diethynylbenzene with benzene-1,4-dicarbaldehyde, C10H6·C8H6O2, (2), are presented. In both cocrystals, a strong nonconventional ethynyl-carbonyl sp-C-H...O hydrogen bond is observed between the components. In cocrystal (1), the C-H...O hydrogen-bond angle is 171.8 (16)° and the H...O and C...O hydrogen-bond distances are 2.200 (19) and 3.139 (2) Å, respectively. In cocrystal (2), the C-H...O hydrogen-bond angle is 172.5 (16)° and the H...O and C...O hydrogen-bond distances are 2.25 (2) and 3.203 (2) Å, respectively.