Comparison of inclusion properties between p-tert-butylcalix[4]arene and p-tert-butylthiacalix[4]arene towards primary alcohols in crystals

Abstract

Powdery crystals of p-tert-butylcalixij4]arene (1), when suspended in primary alcohols with C1-C7 carbon chains, absorb the alcohols to form 1 : 2, 1 : 1 and 2 : 1 (host : guest) inclusion crystals with C1, C2-C4 and C5-C7 alcohols, respectively, whereas powdery crystals of compound 2 absorb only ethanol by the same treatment. In competitive experiments, the crystals of compound 1 preferentially absorb propanol and hexanol among the alcohols that form 1 : 1 and 2 : 1 inclusion crystals, respectively, but the selectivities are inferior to the selectivity of compound 2 towards ethanol. These differences in inclusion properties between compounds 1 and 2 are attributed to the difference in the crystal packing of the inclusion crystals.X-ray analysis reveals that compound 1 constructs a bilayer structure with the aid of a network of the intermolecular CH-π interaction between a methylene group of a host molecule and a benzene ring of an adjacent host molecule. The bilayers are laminated in two different manners depending on the size of guest compounds. A small alcohol is included into the cavity of a host molecule to form 1 : 1 inclusion crystals, whereas a large alcohol is included into a molecular capsule constructed by two host molecules gathered in a head-to-head manner to form 2 : 1 inclusion crystals. The inclusion crystals with the same packing structure have almost the same spaces to accommodate guest molecules, regardless of the guest size, producing good receptivity of compound 1 towards alcohols. On the other hand, compound 2, which lacks methylene bridges, forms a CH-π interaction with the terminal methyl group of an alcohol molecule included into its cavity, and the alcohol molecule forms hydrogen bonds with the hydroxyl groups of an adjacent host molecule to construct a columnar structure. The difference in stability of the columnar structure among the alcohols causes the high inclusion selectivity of compound 2 towards ethanol. CrystEngCommThis journal is

Mechanistic Consideration for the Selective Inclusion of Disubstituted Benzene Isomers with p-tert-Butylcalix[4]arene Crystals

“…Calixarenes, such as p - tert -butylcalix­[4]­arene ( 1 ) and p - tert -butylthiacalix­[4]­arene ( 2 ) (Chart ), are representative examples of host compounds employed in the construction of NMCs, which have “porosity without pores.” The inclusion of organic molecules and inorganic gases has been extensively investigated by the research groups of Atwood, − Ripmeester, − Gorbatchuk, − and Tsue. − Recently, molecular recognition with crystals of calixarene derivatives having channel structures has also been studied by Yamada and Hamada’s group. , Since we succeeded in achieving the selective inclusion of alcohols by crystals of compound 2 , we have extended the guest scope toward carboxylic acids, amines, and alkanes. − The crystal of compound 2 is constructed by self-inclusion dimer complexes and has no channels. We found that such an NMC with no channels can discriminate molecules of similar size and structure by the virtue of the differences in the activation energies (kinetic factor) for the inclusion and in the lattice energies (thermodynamic factor) of the resulting inclusion crystals.…”

“…We found that such an NMC with no channels can discriminate molecules of similar size and structure by the virtue of the differences in the activation energies (kinetic factor) for the inclusion and in the lattice energies (thermodynamic factor) of the resulting inclusion crystals. Recently, the separation of organic molecules by NMCs with no channels has been actively studied. − Although methylene-bridged calixarene 1 also forms a self-inclusion crystal, the guest selectivity toward primary alcohols is poor . Inclusion crystals of compound 1 comprise a stable bilayer structure that is constructed with the aid of cooperative intermolecular CH−π interactions between methylene groups of host molecules and benzene rings of adjacent host molecules .…”

“…Recently, the separation of organic molecules by NMCs with no channels has been actively studied. − Although methylene-bridged calixarene 1 also forms a self-inclusion crystal, the guest selectivity toward primary alcohols is poor . Inclusion crystals of compound 1 comprise a stable bilayer structure that is constructed with the aid of cooperative intermolecular CH−π interactions between methylene groups of host molecules and benzene rings of adjacent host molecules . Depending on the size and shape of guest molecules, the bilayers are arranged in two different manners to form type A (host/guest = 1:1) and type B (host/guest = 2:1) inclusion crystals (Figure ).…”

Inclusion of Amine Isomers with Open-Chain Hosts Having a Partial Structure of p-tert-Butylthiacalixarene

“…On the contrary, the accumulation of host/guest complexes produces a difference in the thermodynamic stabilities of the resulting inclusion crystals with different guest compounds to realize thermodynamic selectivity. We succeeded in the inclusion of alcohols, carboxylic acids, and amines with high guest selectivities using crystals of compound 1 under kinetic or thermodynamic control. Switching of the guest selectivity by changing the solvent polarity or inclusion temperature was also achieved in some cases.…”

Unraveling the Sorption Mechanism of CO2 in a Molecular Crystal without Intrinsic Porosity

“…Calixarene-based molecular crystals are also being considered for gas storage. ,, p - tert -Butylcalix­[4]­arene ( t BC) is the most widely studied calixarene. The t BC molecule has a bowl-like structure whose molecular crystal exhibits significant uptake of a variety of molecules, while retaining its crystal morphology − as well as by altering it . However even the low-density β 0 phase of t BC does not contain channels wide enough to accommodate small molecules, also indicated by the negligible Brunauer–Emmett–Teller surface area from N 2 adsorption measurements .…”