Role of sp-C−H---N Hydrogen Bonding in Crystal Engineering

Evidence supporting the central role of alkynyl sp-C−H---N hydrogen bonds in the formation of discrete molecular complexes as well as one- and two-dimensional bimolecular sp-C−H---N hydrogen bonded networks is presented. The crystal structures of seven bimolecular complexes formed between nitrogen-containing aromatics and compounds containing terminal alkynes are reported. The average N---H distance in these structures is 2.35 Å, well below the sum of the van der Waals’ radii of 2.80 Å, and the average N---H−C bond angle is 173.2°.