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

Abstract

Infrared and Raman spectra over the temperature range room temperature to 74K have been recorded for a range of inclusion compounds of thiourea containing monosubstituted 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 the more abundant. At room temperature the chloro, bromo and cyano substituted guests exist predominantly as the axial conformer, whereas the iodo and isocyanato substituted guests exist as a mixture of both conformers, but with the axial conformer being the more abundant. The iodocyclohexane inclusion compound was the only one to display a temperature dependent change in the intensity ratio of the conformer bands. This could be due to a change in the conformer ratio or to a structural phase change.