This paper probes the propensity for terminal alkynes to form C≡C-H···πinteractions in the solid state, by rationalization of the structural properties of molecular solids in which C≡C-H is the only recognized hydrogen bond donor group, but in which there are different possibleπsystems that may serve as the acceptor for C≡C-H···πinteractions. Theseπsystems are the C≡C-H group itself and the arene ringπsystem. Thus, in the crystal structures of 1,4-diethynylbenzene (redetermined here) and 1,3,5-triethynylbenzene (reported for the first time here) there is competition between the C≡C-H groups and the arene rings as acceptors for C≡C-H···πinteractions. It is found that both structures contain chains of C≡C-H···π(C≡C) interactions - zig-zag chains in the case of 1,4-diethynylbenzene and helical chains in the case of 1,3,5-triethynylbenzene. Neither structure contains any C≡C-H···π(arene) interactions. Cooperativity in the formation of the chains of C≡C-H···π(C≡C) interactions is strongly implicated (although not directly proven) by the results reported here. The conclusions derived here concerning the preferences for the formation of C≡C-H···πinteractions have important implications with regard to the recognition and utilization of weak intermolecular interactions in the structural design of molecular solids.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry