The effect of macrocycle size on the structure-property relationships was studied for inclusion compounds of tert-butylcalix[n]arenes (n=4,5) with volatile organic guests having various molecular size and group composition. Vapor-sorption isotherms, guest-inclusion stoichiometry and Gibbs energy, thermostability parameters and decomposition enthalpies were determined for host-guest compounds (clathrates) obtained using saturation of solid calixarene powder with guest vapor. The increase of the host macrocycle in the studied calixarene pair changes the observed structure-property relationship from the guest-binding selectivity mostly seen in inclusion Gibbs energy to the high sensitivity for guest structure in inclusion stoichiometry. The host with the larger macrocycle has more clathrates with stepwise formation and decomposition. Specific types of guest binding with solid hosts are discussed.
A new principle of quantitative and qualitative analysis of binary organic mixtures is offered, which is based on an ability of calixarene receptor for specific polymorphic transitions related to the composition of the analyzed guest mixture. The ability of tert-butylcalix[6]arene to remember selectively some guests bound from headspace both of pure liquids and their binary mixtures is used. The image of guest mixture remains written in metastable polymorphs of host after partial or complete guest elimination from clathrates. The memory was read using differential scanning calorimetry as the enthalpy of exothermic polymorphic transition of host collapse. This enthalpy monotonously changes with the variation of guests' ratio in mixture, unlike the enthalpies of endothermic pseudopolymorphic transitions of guest release. So, the composition of volatile binary mixture can be estimated using only one receptor and only one its parameter even in absence of preferential binding from a binary mixture of guests. This is an example of a genuine molecular recognition.
The effect of carboxy groups and the stable conformation of tert butylcalix[4]arenes containing four carboxymethoxy substituents at the lower rim on their receptor properties toward organic substances and water was studied for the systems with guest vapor and solid host. For this purpose, the compositions of clathrates formed in these systems, their thermal stability, and parameters of the host-guest affinity were determined by the quartz microbal ance method, thermogravimetry, thermogravimetry combined with differential scanning calorimetry and mass spectrometry, and static headspace gas chromatography. The introduc tion of four carboxymethoxy groups into tert butylthiacalix[4]arene enhances its receptor capacity and affinity to water and aliphatic alcohols and decreases the thermal stability of the most part of the studied clathrates with hydrophobic guests except benzene. The studied tert butylthiacalix[4]arene derivatives can be promising receptors for use in mass sensitive sensors of the quartz microbalance type to methanol and ethanol vapors.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.