Halogen Bonding in Iodo-perfluoroalkane/Pyridine Mixtures

Abstract

Mole fraction and temperature studies of halogen bonding between 1-iodo-perfluorobutane, 1-iodo-perfluorohexane, or 2-iodo-perfluoropropane and pyridine were performed using noisy light-based coherent anti-Stokes Raman scattering (I((2)) CARS) spectroscopy. The ring breathing mode of pyridine both is highly sensitive to halogen bonding and provides a strong I((2)) CARS signal. As the lone pair electrons from the pyridinyl nitrogen interact with the sigma-hole on the iodine from the iodo-perfluoroalkane, the ring breathing mode of pyridine blue-shifts proportionately with the strength of the interaction. The measured blue shift for halogen bonding of pyridine and all three iodo-perfluoroalkanes is comparable to that for hydrogen bonding between pyridine and water. 2-Iodo-perfluoropropane displays thermodynamic behavior that is different from that of the 1-iodo-perfluoroalkanes, which suggests a fundamental difference at the molecular level. A potential explanation of this difference is offered and discussed.

The halogen bond with isocyano carbon reduces isocyanide odor

“…Single-crystal XRD is the most conventional method to verify geometrical parameters of XB. NMR 35,36 and IR/ Raman 37,38 spectroscopies could also be used for XB recognition in the solid state; however, these techniques are not common as they provide only collateral identification of XB by detection of spectral changes for bonded and nonbonded forms; these changes are usually less significant in the solid state than in solutions. Another complication is that the solid-state NMR for XB donor sites (Cl, Br, and I) usually gives very broad signals because of the large quadruple moments of their NMR-active nuclei and thus it requires the application of the ultrahigh field NMR spectroscopy to obtain accurate data 35,[39][40][41] .…”

Site-selective assembly between 1,8-diiodoperfluorooctane and 4,7,8,11-tetraazahelicene driven by halogen bonding

“…the 1,8-diiodoperfluoroalkane 1 (Scheme 1), are among the most commonly employed XB-donors (7). Perfluorocarbon residues are strongly electron-withdrawing, and in addition, the -(CF 2 ) n -chain in a perfluoroalkane is significantly more stiff than the -(CH 2 ) n -chain in its hydrocarbon analogue and this confers an extra advantage in terms of preorganization and structural control.…”

“…For instance, monoazahelicenes have been already shown to be able to coordinate silver cations via quinolinic and isoquinolinic nitrogen atoms positioned in the internal rim of the helicenes, affording 2:1 (helicene/Ag + ) complexes in the solid state (10). The 4,7,8,11-tetraazahelicene 2 (Scheme 1), having two different sets of nitrogen atoms (pyridinic/quinolinic and pyridazinic/cinnolinic), is an ideal candidate to study the site-selectivity of XB-formation in polynitrogen aromatic systems. For the same reason, 2 was selected also as a good candidate for testing computational methods as tools for predicting the site-selectivity of the XB, whenever a structural ambiguity is present.…”

Salivary gland disorders and diseases: Diagnosis and management

“…It is recognized that the interaction between pyridine and the surroundings can be reflected through its ring breathing mode, which is more prone to be perturbed by H‐bond than the triangle mode, and the magnitude of frequency blue shift increases with the strength of H‐bonding. For example, in pyridine/HCONH 2 , pyridine/H 2 O, and pyridine/CH 3 COOH systems, the ring breathing mode has blue shifts of 5, 8, and 14 cm −1 , respectively 15, whereas in the chloroform and bromoform systems 19, the blue shifts in the ring breathing mode were about 1–2 cm −1 .…”