Halogen bonding stabilizes a cis-azobenzene derivative in the solid state: A crystallographic study

Marco Saccone, Antti Siiskonen, Francisco Fernandez-Palacio, Arri Priimagi*, Giancarlo Terraneo, Giuseppe Resnati, Pierangelo Metrangolo

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

9 Citations (Scopus)


Crystals of trans- and cis-isomers of a fluorinated azobenzene derivative have been prepared and characterized by single-crystal X-ray diffraction. The presence of F atoms on the aromatic core of the azobenzene increases the lifetime of the metastable cis-isomer, allowing single crystals of the cis-azobenzene to be grown. Structural analysis on the cis-azobenzene, complemented with density functional theory calculations, highlights the active role of the halogen-bond contact (N...I synthon) in promoting the stabilization of the cis-isomer. The presence of a long aliphatic chain on the azobenzene unit induces a phase segregation that stabilizes the molecular arrangement for both the trans- and cis-isomers. Due to the rarity of cis-azobenzene crystal structures in the literature, our paper makes a step towards understanding the role of non-covalent interactions in driving the packing of metastable azobenzene isomers. This is expected to be important in the future rational design of solid-state, photoresponsive materials based on halogen bonding. We show by single-crystal X-ray diffraction studies and computational analysis that halogen bonding can stabilize a metastable cis-azobenzene derivative in the solid state.

Original languageEnglish
Pages (from-to)227-233
Number of pages7
JournalActa Crystallographica. Section B: Structural Science, Crystal Engineering and Materials
Issue number2
Publication statusPublished - 1 Apr 2017
MoE publication typeA1 Journal article-refereed


  • azobenzene
  • halogen bonding
  • isomerization


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