Clathrate and inclusion compounds. 14. Variable temperature vibrational spectroscopic studies of monosubstituted cyclohexane guests in thiourea

Infrared and Raman spectra over the temperature rang room temperature to 74 K have been recorded for a range of inclusion compounds of thiourea contain ing monosubsituted cyclohexanes C6H11X (X = Cl, Br, I, CN, NCO) as guests. The liquid phase of all the cyclohexanes consists of an equilibrium mixture of axial and equatorial conformers, with the equatorial conformer being th e more abundant. At room temperature the chloro, bromo and cyano substitute d guests exist predominantly as the axial conformer, whereas the iodo and i socyanato substituted guests exist as a mixture of both conformers, but wit h the axial conformer being the more abundant. The iodocyclohexane inclusio n compound was the only one to display a temperature dependent change in th e intensity ratio of the conformer bands. This could be due to a change in the conformer ratio or to a structural phase change.