The Effect of Pressure on Halogen Bonding in 4-Iodobenzonitrile

Molecules

SimonJ. Teat¹  ChristineM. Beavers¹  EarlF. O’Bannon¹  Simon Parsons²  ClaireL. Hobday²  Nico Giordano²  KonstantinV. Kamenev³  Sergejs Afanasjevs³  Javier Ruiz-Fuertes⁴  Rafael Valiente⁵ 

[1] Advanced Light Source, 1 Cyclotron Road, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA;Centre for Science at Extreme Conditions and EaStCHEM School of Chemistry, The University of Edinburgh, King’s Buildings, West Mains Road, Edinburgh, Scotland EH9 3FD, UK;Centre for Science at Extreme Conditions and School of Engineering, The University of Edinburgh, King’s Buildings, West Mains Road, Edinburgh, Scotland EH9 3FD, UK;Dpto. DCITIMAC, Facultad de Ciencias, Universidad de Cantabria, 39005 Santander, Spain;Dpto. Física Aplicada, Facultad de Ciencias, Universidad de Cantabria-IDIVAL, 39005 Santander, Spain;

关键词: high pressure;    halogen bonding;    intermolecular interactions;   

DOI  :  10.3390/molecules24102018

来源: DOAJ

【 摘 要 】

The crystal structure of 4-iodobenzonitrile, which is monoclinic (space group I2/a) under ambient conditions, contains chains of molecules linked through C≡N···I halogen-bonds. The chains interact through CH···I, CH···N and π-stacking contacts. The crystal structure remains in the same phase up to 5.0 GPa, the b axis compressing by 3.3%, and the a and c axes by 12.3 and 10.9 %. Since the chains are exactly aligned with the crystallographic b axis these data characterise the compressibility of the I···N interaction relative to the inter-chain interactions, and indicate that the halogen bond is the most robust intermolecular interaction in the structure, shortening from 3.168(4) at ambient pressure to 2.840(1) Å at 5.0 GPa. The π∙∙∙π contacts are most sensitive to pressure, and in one case the perpendicular stacking distance shortens from 3.6420(8) to 3.139(4) Å. Packing energy calculations (PIXEL) indicate that the π∙∙∙π interactions have been distorted into a destabilising region of their potentials at 5.0 GPa. The structure undergoes a transition to a triclinic ( $P\overline{1}$ ) phase at 5.5 GPa. Over the course of the transition, the initially colourless and transparent crystal darkens on account of formation of microscopic cracks. The resistance drops by 10% and the optical transmittance drops by almost two orders of magnitude. The I···N bond increases in length to 2.928(10) Å and become less linear [−1 and the mixed C-I/I..N stretching frequency observed by Raman spectroscopy increases from 249 to 252 cm⁻¹. The driving force of the transition is shown to be relief of strain built-up in the π∙∙∙π interactions rather than minimisation of the molar volume. The triclinic phase persists up to 8.1 GPa.

【 授权许可】

Unknown