Abstract
Infrared spectroscopic methods were applied for investigations on the states of molecules trapped in thiourea-d4 channels. It was found that, in the spectra of thiourea-d4 adducts, absorption bands due to guest molecules could be observed in the regions between 2800 and 2600 cm-1, 2200 and 1600 cm-1, 1300 and 990 cm-1 and 790 and 680 cm-1. Thus, nearly all absorption bands of guest molecules were observed in sodium chloride region by the use of both thiourea and thiourea-d4 adducts, except the regions where CH2 stretching and bending vibrations absorb. As an example, bands due to the axial isomers of halogenated cyclohexanes were determined by this technique. Relatively free rotation or random orientation of dioxane or cyclohexane molecules in thiourea channels was also supported by the present work. From the comparison with the orientation of cyclopentanone or cyclohexanone molecule in thiourea channels, it is suggested that electric dipole forces would operate to orientate guest molecules in channels.
