Guest-guest interactions in urea inclusion compounds

Different types of urea inclusion compounds have been studied to test the importance of the molecular interactions between guests in urea inclusion compounds. Experimental evidence has been obtained by the EPR spectra of guest radicals obtained by room temperature g ray irradiation of the inclusion compounds. The guest-guest intra-channel interactions are very important in the case of tridecandioic and tetradecandioic dicarboxylic acids guests which give rise to strong inter-molecular hydrogen bonding between the carboxylic groups. It is found that the molecular conformation of the tetradecanoic acid is strongly distorted to fit to the host channel dimensions. The interactions between guest molecules included in adjacent host channels have been modulated by varying the relative guest composition in a mixed 10-nonadecanone/nonadecane inclusion compound. It is shown that the molecular reorientation of the 10-nonadecanone guest becomes faster by increasing the nonadecane percentage as a consequence of the reduced inter-channel interactions.