Acta Crystallographica Section B

Structural Science

Volume 56, Part 6 (December 2000)

research papers

Acta Cryst. (2000). B56, 1071-1079 [ doi:10.1107/S010876810001154X ]

Crystal engineering in the gem-alkynol family; synthon repetitivity and topological similarity in diphenylethynylmethanols: structures that lack O-HO hydrogen bonds

C. Bilton, J. A. K. Howard, N. N. L. Madhavi, A. Nangia, G. R. Desiraju, F. H. Allen and C. C. Wilson

Abstract: The structures of four para-substituted derivatives of diphenylethynylmethanol have been determined [ditolylethynylmethanol, di(4-chlorophenyl)ethynylmethanol, di(4-bromophenyl)ethynylmethanol and bis(4,4'-biphenylyl)ethynylmethanol]. The dimethyl, dichloro, dibromo and diphenyl compounds have been analysed using X-ray diffraction at 150 K, and the dichloro compound has also been studied using neutron diffraction at 150 K. In common with the parent diphenylethynylmethanol [Garcia, Ramos, Rodriguez & Fronczek (1995). Acta Cryst. C51, 2674-2676], all four derivatives fail to form the expected strong O-HO hydrogen bonds due to steric hindrance. Instead, the supramolecular structural organization in this family of gem-alkynols is mediated by a variety of weaker interactions. The two most acidic protons, O-H and C [triple bond] C-H, participate in weak hydrogen bonds to [pi] -acceptors, forming synthons that stabilize all five structures. These primary interactions are reinforced by a variety of other weak hydrogen bonds involving C-H donors and the hydroxy-O as an acceptor, and by halogenhalogen interactions in the dichloro and dibromo compounds.

Keywords: gem-Alkynol; Synthon repetitivity; Topological similarity.