$C-X\cdots\pi$ halogen and $C-H\cdots\pi$ hydrogen bonding

Ondertitel:interactions of $CF_{3}X$ (X = Cl, Br, I or H) with ethene and propene

Using FTIR and Raman spectroscopy, the formation of halogen bonded complexes of the trifluorohalomethanes CF(3)Cl, CF(3)Br and CF(3)I with ethene and propene dissolved in liquid argon has been investigated. For CF(3)Br and CF(3)I, evidence was found for the formation of C-X center dot center dot center dot pi halogen bonded 1 : 1 complexes. At a higher ratio of CF(3)I/propene, weak absorptions due to a 2 : 1 complex were also observed. Using spectra recorded at different temperatures, the complexation enthalpies for the complexes were determined to be -5.3(2) kJ mol(-1) for CF(3)Br center dot ethene, -7.5(2) kJ mol(-1) for CF(3)I center dot ethene, -5.6(1) kJ mol(-1) for CF(3)Br center dot propene, -8.8(1) kJ mol(-1) for CF(3)I center dot propene and -16.5(6) kJ mol(-1) for (CF(3)I center dot)(2)propene. The complexation enthalpies of the hydrogen bonded counterparts, with CF(3)H as the Lewis acid, were determined to be -4.6(4) kJ mol(-1) for CF(3)H center dot ethene and -5.1(2) kJ mol(-1) for CF(3)H center dot propene. For both hydrogen bonded complexes, a blue shift, by + 4.8 and + 4.0 cm(-1), respectively, was observed for the C-H stretching mode. The results from the cryospectroscopic study are compared with ab initio calculations at the MP2/aug-cc-pVDZ(-PP) level.

Jaar van publicatie:2012

Trefwoorden:A1 Journal article

BOF-keylabel:ja

BOF-publication weight:1

CSS-citation score:2

Authors from:Higher Education

Toegankelijkheid:Closed