Structural Features and Thermal Stability of 25,26,27,28-Tetrahydroxycalix[4]arene Molecular Complexes with Solvents

Abstract

A single crystal of 25,26,27,28-tetrahydroxycalix[4]arene molecular complex with n-hexane was grown by slow evaporation of a solution in n-hexane allowing a complete elucidation of its structure. For the first time a 25,26,27,28tetrahydroxycalix[4]arene molecular complex with toluene was obtained. In addition, its thermal stability was studied. The kinetic sorption curves of acetone, acetonitrile, nhexane, and toluene saturated vapors within 25,26,27,28-tetrahydroxycalix[4]arene were derived experimentally. It was shown that the kinetic sorption curve of acetonitrile saturated vapor within 25,26,27,28-tetrahydroxycalix[4]arene has a distinct peak corresponding to the 1:1 stoichiometry. It was suggested that the structural reorganization of 25,26,27,28-tetrahydroxycalix[4]arene provides transport of acetonitrile molecules into the molecular crystal and subsequent complexation with the formation of a thermodynamically stable hexagonal structure. A conclusion was drawn that the high thermal stability of 25,26,27,28-tetrahydroxycalix[4]arene solvates is due to strict compliance with the shape and size of the "guest" molecule and "host" cavity size.

Drastic and subtle thermally and gas-induced transformations of pure 4-tert-butylcalix[4]arene

“…It can be assumed that structural reorganization of the host during the sorption provides the transport of the guest in the molecular crystal, and subsequent complexation with formation of a thermodynamically stable structure. 39…”

Self‐Assembly of Bowlic Supramolecules on Graphene Imaged at the Individual Molecular Level using Heavy Atom Tagging

“…[ 27 ] Likewise, the self‐assembly of calix[n]arenes in crystals was substantially influenced by the type and number of substituents as well as crystallization solvent, indicating that the head‐to‐tail bowl stacking is challenging to observe. [ 26,28–30 ]…”

“…[27] Likewise, the self-assembly of calix[n]arenes in crystals was substantially influenced by the type and number of substituents as well as crystallization solvent, indicating that the head-to-tail bowl stacking is challenging to observe. [26,[28][29][30] An advanced imaging technique such as transmission electron microscopy (TEM) has been used to elucidate the self-assembly of bowlic calix [n]arenes, yet only large nanoscale features (≈100 nm) of supramolecular aggregation were visualized. [31][32][33] The vesicular nanoaggregates imply the side-by-side…”

Lower rim dimerization of a calixarene through the encapsulation of sodium ions

“…1 Our comprehension of the phenomenon driving the inclusion of guests into cavities has progressed much on the basis of studies dealing with calixarenes. 2 From such knowledge, calixarenes have been designed as carriers for transport and controlled release of drugs, 3 gas absorbers, 4 metal and drug sensors, 5 pre-concentration agents in separation techniques, 6 and mobile or stationary phases in liquid chromatography, 7 among several others. Besides directly invoking the host-guest phenomenon in these uses, functionalized calixarenes have been used as catalysts 8 and photoluminescent/fluorescent probes.…”

“…12 In this nanocapsule, cone-shaped calixarene molecules are tail-to-tail arranged so that carboxylate oxygens from different units can bind to the same metal ion in addition to the molecules' coordination into the minor cavity of each unit through methoxy and carboxylate oxygens. Concerning its shape, it resembles a calix [4]tube designed with four ethylene linkages covalently connecting two calix [4]arene units through their lower rim. 13 In this calixarene-metal structure, however, the nanocapsules are bonded together to form a threedimensional coordination polymer.…”