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. 2018 Jun 22;5(Pt 4):491-496.
doi: 10.1107/S2052252518007583. eCollection 2018 Jul 1.

Structural flexibility of halogen bonds showed in a single-crystal-to-single-crystal [2+2] photodimerization

Michael A Sinnwell  1 , Jared N Blad  1 , Logan R Thomas  1 , Leonard R MacGillivray  1
Affiliations

Structural flexibility of halogen bonds showed in a single-crystal-to-single-crystal [2+2] photodimerization

Michael A Sinnwell et al. IUCrJ. .

Abstract

Halogen bonds have emerged as noncovalent forces that govern the assembly of molecules in organic solids with a degree of reliability akin to hydrogen bonds. Although the structure-directing roles of halogen bonds are often compared to hydrogen bonds, general knowledge concerning the fundamental structural behavior of halogen bonds has had limited opportunity to develop. Following an investigation of solid-state reactions involving organic syntheses and the development of photoresponsive materials, this work demonstrates the ability of the components of intermolecular N⋯I halogen bonding - a 'workhorse' interaction for the crystal engineer - to support a single-crystal-to-single-crystal [2+2] photodimerization. A comparison is provided of the geometric changes experienced by the halogen-bonded components in the single-crystal reaction to the current crystal landscape of N⋯I halogen bonds, as derived from the Cambridge Structural Database. Specifically, a linear-to-bent type of deformation of the halogen-bonded components was observed, which is expected to support the development of functional halogen-bonded materials containing molecules that can undergo movements in close-packed crystal environments.

Keywords: co-crystals; crystal engineering; framework-structured solids and amorphous materials; halogen bonds; molecular crystals; organic solid-state reactions; photodimerization; single-crystal-to-single-crystal reaction; solid-state reactivity; supramolecular chemistry.

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Figures

Figure 1
Figure 1
X-ray structure of (I4F16cb)·2(bpe): (a) C=C distances (inset: halogen-bonding metrics) and (b) layers of chains.
Figure 2
Figure 2
Table of halogen-bond metrics and changes in the geometries of components of (I4F16cb)·2(bpe) and (I4F16cb)·(tpcb) with comparisons to the CSD.
Figure 3
Figure 3
X-ray structure of (I4F16cb)·(tpcb) showing cyclo­butane formation (inset: halogen-bonding metrics).
Figure 4
Figure 4
IsoStar scatterplots: XB1 (left) and XB2 (right) of (I4F16cb)·2(bpe) (gray) and (I4F16cb)·(tpcb) (black). Highest occupied XB1 and XB2 in one quadrant (inset: criteria for CSD search).
See this image and copyright information in PMC

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