Blue-Shifting or Red-Shifting Hydrogen Bonding? Predictions for Haloform Complexes with Dimethyl Ether on the Basis of Perturbation Theory

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2004-07, Vol.108 (28), p.6059-6064
• Main Authors: Herrebout, Wouter A, Delanoye, Sofie N, van der Veken, Benjamin J
• Format: Article
• Language: English
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp049365m

Frequency shifts of the C−H stretching mode, ν1, of the haloforms CHF3, CHClF2, CHCl2F, and CHCl3 because of complexation with dimethyl ether have been calculated from an ab initio interaction potential between the two molecules, using a perturbative approach. The shift is described as a sum of two terms, a first due to a stiffening of the C−H bond, the second due to the attractive or repulsive nature of the interaction of the C−H bond with the Lewis base. For CHF3 through CHCl2F, both terms are positive, resulting in an overall blue shift of ν1; for the complex with CHCl3, the attractive interaction with the Lewis base causes a red shift which is larger than the blue shift because of the stiffening of the C−H bond, resulting in a small overall red shift. The calculated results are compared with experimental literature data on these complexes.