1452886-44-0Relevant academic research and scientific papers
Direct investigation of halogen bonds by solid-state multinuclear magnetic resonance spectroscopy and molecular orbital analysis
Viger-Gravel, Jasmine,Leclerc, Sophie,Korobkov, Ilia,Bryce, David L.
, p. 6929 - 6942 (2014/06/09)
Noncovalent interactions play a ubiquitous role in the structure, stability, and reactivity of a wide range of molecular and ionic cocrystals, pharmaceuticals, materials, and biomolecules. The halogen bond continues to be the focus of much attention, due in part to its strength and unique directionality. Here, we report a multifaceted experimental and computational study of halogen bonds in the solid state. A series of cocrystals of three different diiodobenzene molecules and various onium halide (Cl- or Br-) salts, designed to exhibit moderately strong halogen bonds (C-I···X-) in the absence of competing hydrogen bonds, has been prepared and characterized by single-crystal X-ray diffraction. Interestingly, a wide range of geometries about the halide anion are observed. 35/37Cl and 79/81Br solid-state NMR spectroscopy is applied to characterize the nuclear quadrupolar coupling constants (C Q) and asymmetry parameters (?Q) for the halogen-bonded anions at the center of bonding environments ranging from approximately linear to distorted square planar to octahedral. The relationship between the halogen bond environment and the quadrupolar parameters is elucidated through a natural localized molecular orbital (NLMO) analysis in the framework of density functional theory (DFT). These calculations reveal that the lone pair type orbitals on the halogen-bonded anion govern the magnitude and orientation of the quadrupolar tensor as the geometry about the anion is systematically altered. In-C-I···X -···I-C-environments, the value of ?Q is well-correlated to the I···X -···I angle. 13C NMR and DFT calculations show a correlation between chemical shifts and halogen bond strength (through the C-I distance) in o-diiodotetrafluorobenzene cocrystals. Overall, this work provides a chemically intuitive understanding of the connection between the geometry and electronic structure of halogen bonds and various NMR parameters with the aid of NLMO analysis.
Correlation between 13C chemical shifts and the halogen bonding environment in a series of solid para-diiodotetrafluorobenzene complexes
Viger-Gravel, Jasmine,Leclerc, Sophie,Korobkov, Ilia,Bryce, David L.
, p. 3168 - 3177 (2013/06/04)
The co-crystallization of para-diiodotetrafluorobenzene (p-DITFB) with ammonium and phosphonium halide (Cl- and Br-) salts afforded four new compounds, [(n-Bu4PCl)(p-DITFB)] (2), [(n-Bu 4NBr)(p-DITFB)] (3), [(n-Bu4PBr)(p-DITFB)] (4), and [(EtPh3PBr)2(p-DITFB)] (5), that exhibit moderately strong halogen bonding interactions. They have been characterized by single-crystal X-ray diffraction and 13C solid-state nuclear magnetic resonance (SSNMR) spectroscopy in magnetic fields of 9.4 and 21.1 T. The X-ray crystallography shows that in 2, 3, and 4, the halide is ditopic and forms long polymeric zigzag chains, whereas the bromide in 5 forms a dianionic species when involved in halogen bonding interactions. The NMR data, when combined with zeroth-order regular approximation density functional theory (ZORA-DFT) calculations, provide insight into the relationship between the strength of the halogen bond and the 13C isotropic chemical shift. When the carbon-iodine bond length increases, the 13C chemical shift also increases. Further insights into the relationship between halogen bonding and the 13C chemical shifts are obtained through additional systematic ZORA-DFT calculations as a function of the halogen bonding environment.
