Spectroscopic and Thermal Characterization of the Host-Guest Interactions between α-, β-, and γ-cyclodextrins and vanadocene dichloride.

Host-guest interactions between α-, β-, and γ-cyclodextrins and vanadocene dichloride (Cp(2)VCl(2)) have been investigated by a combination of thermogravimetric analysis, differential scanning calorimeters, PXRD and solid state and solution EPR spectroscopy. The solid state results demonstrated that only β- and γ-cyclodextrins form 1:1 inclusion complexes, while α-cyclodextrin does not form an inclusion complex with Cp(2)VCl(2). The β- and γ-CD-Cp(2)VCl(2) inclusion complexes exhibited anisotropic electron-(51)V (I = 7/2) hyperfine coupling constants whereas the α-CD- Cp(2)VCl(2) system showed only an asymmetric peak with no anisotropic hyperfine constant. On the other hand, solution EPR spectroscopy showed that α-CD may be involved in weak host-guest interactions in equilibrium with free vanadocene species.