Evaluating the role of sp-C-H…N hydrogen bonds in the structure of cocrystals formed between 1,4-diethynyl-2,3,5,6-tetramethylbenzene and each of 1,4-diaza-bicyclo[2.2.2]octane and 4,4’-dipyridine

Abstract

1,4-Diethynyl-2,3,5,6-tetramethylbenzene crystallizes in the orthorhombic space group Cmca and the structure of features weak sp-C-H···π interactions. The 1:1 cocrystal formed between 1,4-diethynyl-2,3,5,6-tetramethylbenzene and 1,4-diaza-bicyclo[2.2.2]octane crystallizes in the triclinic space group P-1, while the cocrystal formed between 1,4-diethynyl-2,3,5,6-tetramethylbenzene and 4,4’-bipyridine crystallizes in the monoclinic space group P2₁. Both cocrystals feature sp-C-H···N hydrogen bonds between the components. Analysis of the Hirschfeld surface within the cocrystals confirm that the C-H—N hydrogen bond corresponds to the closest atom-to-atom contact in the cocrystals. Indeed, the C-H—N separation range in the cocrystals ranges from 2.32 to 2.47 Å, corresponding to 84–90% of the sum of the van der Waals radii. Calculation of the intermolecular interaction energies within each crystal structure reveal that π-stacking interactions dominate even though the aromatic molecules are significantly offset. The C-H—N interaction although weaker than the π-stacking interactions should be considered as a major driving force for the formation of these cocrystals.

Graphical abstract

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