Exploring the C-X…π Halogen Bonding Motif: An Infrared and Raman Study of the Complexes of CF3X (X = Cl, Br and I) with the Aromatic Model Compounds Benzene and Toluene

Molecules

Nick Nagels¹  Dieter Hauchecorne¹ 

[1] id="af1-molecules-18-06829">Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgi

关键词: halogen bonding;    C-X···π interactions;    infrared spectroscopy;    Raman spectroscopy;    cryosolutions;   

DOI  :  10.3390/molecules18066829

来源: mdpi

【 摘 要 】

The formation of halogen bonded complexes formed between the trifluorohalomethanes CF₃Cl, CF₃Br and CF₃I and the Lewis bases benzene and toluene at temperatures below 150K was investigated using FTIR and Raman spectroscopy. Experiments using liquid krypton as solvent show that for both CF₃Br and CF₃I substantial fractions of the monomers can be involved in 1:1 complexes. In addition, weak absorptions illustrating the formation of 2:1 complexes between CF₃I and benzene are observed. Using spectra recorded at temperatures between 120 and 140 K, observed information on the relative stability was obtained for all complexes by determining the complexation enthalpies in solution. The resulting values for CF₃Br·benzene, CF₃I·benzene and (CF₃I)₂·benzene are −6.5(3), −7.6(2) and −14.5(9) kJ mol⁻¹. The values for CF₃Br·toluene and CF₃I·toluene are −6.2(5) and −7.4(5) kJ mol⁻¹. The experimental complexation enthalpies are compared with theoretical data obtained by combining results from MP2/aug-cc-pVDZ(-PP) and MP2/aug-cc-pVTZ(-PP) ab initio calculations, from statistical thermodynamical calculations and from Monte Carlo Free Energy Perturbation simulations. The data are also compared with results derived for other C-X···π halogen bonded complexes involving unsaturated Lewis bases such as ethene and ethyne.

【 授权许可】

CC BY   
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