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, CH·CHO, (1), and the 1:1 cocrystal of 1,4-diethynylbenzene with benzene-1,4-dicarbaldehyde, CH·CHO, (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.

Unexpected beauty and diversity in the structures of three homologous 4,5-dialkoxy-1-ethynyl-2-nitrobenzenes: the subtle interplay between intermolecular C—H...O hydrogen bonds and alkyl chain length

“…In that study, we demonstrated that the sp-C-HÁ Á ÁN hydrogen bond between dipyridines and diethynylbenzenes controlled the formation of cocrystals. In contrast, the sp-C-HÁ Á ÁO(carbonyl) hydrogen-bonding interaction was less efficient, in our hands, as a driving force for cocrystallization of different molecules which was significantly less predictable (Bosch, 2016). In a separate study, we investigated the structure of two ortho-nitrophenylacetylenes and observed unusual C-HÁ Á ÁO interactions (Bosch & Jeffries, 2016), so we decided to further investigate C-HÁ Á ÁO 2 N interactions in three 4,5-dialkoxy-1-ethynyl-2-nitrobenzenes, namely 1-ethynyl-2-nitro-4,5-dipropoxybenzene, (1), 1,2-dibutoxy-4-ethynyl-5-nitrobenzene, (2), and 1-ethynyl-2-nitro-4,5-dipentoxybenzene, (3) (see Scheme).…”

The synergistic cooperation of NH⋯O and CH⋯O hydrogen bonds in the structures of three new phosphoric triamides

“…[14] The weak hydrogen bonds based on C-H donors are important both as secondary and, in fewer cases, as primary interactions in determining crystal structures, in the stabilization of inclusion complexes and in recognition processes. [13,15] From various weak CHX (X = O, N, Cl, π and so on) hydrogen bonding interactions, investigation has been especially concentrated on the CHO interactions [16,17] and such interactions are the best known of all weak hydrogen bond types. That is why several reviews have described these developments and also the historical background of the research on CHO hydrogen bonds in the fields of general structural chemistry [18] and of structural biology.…”