Quantifying Host-Guest Interaction Energies in Clathrates of Dianin's Compound

© 2016 American Chemical Society.
The subtle intermolecular host-guest interaction energies have been quantified for 17 different clathrates of the Dianin's compound. Energy framework analysis of the host structure reveals that, in addition to strong electrostatic forces due to H-bonding, the framework is stabilized by very strong dispersion interactions, resulting in a three-dimensional energy framework. Compared to the host framework, the host-guest interactions are rather weak, and the enclathration only perturbs the host energy framework. Larger guest molecules result in more attractive host-guest interactions, although the shape of the guest molecule is also found to be important. Easy rotation about the c-axis was found for the hexane guest molecule, while the rotation is hindered in the cases of CCl4, CCl3CN, and C(CH3)3CN. For the Dianin clathrates containing the C(CH3)3CN or the acetone guest species, attractive interaction energies between guest molecules in adjacent cavities suggest short-range ordering of the guest molecules. For the clathrates containing multiple guest molecules per cavity, intermolecular interaction energies were used to determine probable guest molecule configurations. In the same way, simple energy calculations like the ones presented here can help crystallographers solve disordered molecular structures by discarding unstable configurations.