Host-guest chemistry and chemical sensors:: FT-IR-analysis and spectra simulation of CDCl3 inclusion

Host-guest principles are put into action advantageously by cyclodextrins that give remarkable sensor responses to halogenated hydrocarbons on mass-sensitive devices such as QMB (quartz micro balance) and SAW (surface acoustic wave) resonators. Modifications of the structure can tune the compound to different analytes and molecular modeling allows us to understand and predict specific host-guest interactions. The FT-IR analysis of CDCl3, incorporated into a partially methylated cyclodextrine, yields an astonishingly strong band shift of about 50 cm(-1) to lower wave numbers, in contrast to the permethylated product that shows a displaced band of 10 cm(-1) for the C-D stretching vibration. The explanation can be given by semiempirical methods and force field calculations. Two CDCl3 binding sites are revealed, one being a multicentered inclusion (<(nu)over tilde> similar to 2195 cm(-1)) of CDCl3 at the upper rim of the beta-cyclodextrine cone, whereas the other is incorporated within the cavity (<(nu)over tilde> similar to 2240 cm(-1)).