Thermal behavior of cyclodextrin/adamantane host/guest inclusion complex in an aqueous media

Abstract

Understanding the thermal behavior of cyclodextrin/adamantane (CD/Ad) host/guest inclusion complex, and the effect of CD type, i.e., α, β, and γ, on their hybridization are fundamentally attractive to find broad contemporary applications toward improving efficient drug delivery systems. In this work, β-cyclodextrin was found as the best host to capture the Ad guest with the minimum intermolecular interaction energy of −11.996 ± 0.026 kcal/mol. This behavior was due to the perfect size match of adamantane with a diameter of 6.49 Å into β-cyclodextrin. It was observed that adamantane was supported by all sides of the inner wall of β-cyclodextrin, while the guest interacted with only one side of the inner wall of γ-cyclodextrin. The results proved that rising the solution temperature has prevented the formation of a host/guest inclusion complex, at the temperature range of 330–340 K. Deep molecular view into the solubility of adamantane showed that the failure of non-bonded interactions of CD-Ad with temperature led to the entrance of water molecules into the hollow part of the β-cyclodextrin created an obstacle against the entrance of the guest. According to the interactional achievements, the electrostatic contribution of the host-water and the dispersive contribution of guest-water led to reducing the interaction energy of host–guest with the temperature. The present research offers some insight into the design of β-cyclodextrin/adamantane-based host/guest assemblies to form a thermoreversible hydrogel in an aqueous media.