Arylethynyl Helices Supported by π-Stacking and Halogen Bonding

Abstract

Co-crystallization of a pyridyl-containing arylethynyl (AE) moiety with 1,4-diiodotetrafluorobenzene leads to unique, figure-eight shaped helical motifs within the crystal lattice. A slight twist in the AE backbone allows each AE unit to simultaneously interact with haloarene units that are stacked on top of one another. Left-handed (M) and right-handed (P) helices are interspersed in a regular pattern throughout the crystal. The major driving forces for assembly are 1) halogen bonding between the pyridyl nitrogen atoms and the iodine substituents of the haloarene, with N⋅⋅⋅I distances between 2.81 and 2.84 Å, and 2) π-π stacking of the haloarenes, with distances of approximately 3.57 Å between centroids. Halogen bonding and π-π stacking not only work in concert, but also seem to mutually enhance one another. Calculations suggest that the presence of π-π stacking modestly intensifies the halogen bonding interaction by <0.2 kcal/mol; likewise, halogen bonding to the haloarene enhances the π-π stacking interaction by 0.59 kcal/mol.

Department(s)

Chemistry and Biochemistry

Document Type

Article

DOI

https://doi.org/10.1002/cplu.202100104

Keywords

alkynes, arenes, crystal engineering, halogen bonding, π-π stacking

Publication Date

5-1-2021

Journal Title

ChemPlusChem

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