Halogen bonding stabilizes a cis‐azobenzene derivative in the solid state: a crystallographic study. Issue 2 (1st April 2017)

• Record Type: Journal Article
• Authors: Saccone, Marco; Siiskonen, Antti; Fernandez-Palacio, Franisco; Priimagi, Arri; Terraneo, Giancarlo; Resnati, Giuseppe; Metrangolo, Pierangelo
• Is Part Of: Acta crystallographica. Volume 73:Issue 2(2017:Apr.)
• Page Start: 227
• Page End: 233
• Publication Date: 2017-04-01
• Subjects: azobenzene -- halogen bonding -- isomerization
• DOI: 10.1107/S2052520617003444
• Languages: English
• ISSNs: 2052-5206

Abstract

Abstract : 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. Abstract : 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.