Confinement of Water Pentamers within the Crystals of a Reduced Cyclotribenzoin

Abstract

Reduction of cyclotribenzoin with sodium borohydride produces a cone-shaped hexaol. Crystals of this hexaol, obtained from wet tetrahydrofuran, encapsulate clusters of five water molecules in an idealized hydrogen-bonded arrangement. The water pentamer is stabilized by hydrogen bonding with the -OH groups of the hexaol, and [O-H⋅⋅⋅π] interactions with the benzene rings of the reduced cyclotribenzoin.

Porous Organic Compounds – Small Pores on the Rise

“…These results make Ac‐B2 a promising candidate for CO 2 capture, flue gas separation and natural gas upgrading. In addition, the benzoin motif present in cyclobenzoins could either be reduced (NaBH 4 ) [30h] or oxidized (HNO 3 ) to the corresponding hydrobenzoins [30e] or benzils [30f] . Hence further modifications by imine condensation with ortho ‐diamines allow property fine tuning or crosslinking of the macrocycles to form POPs [30b] .…”

Formation of a Metallomacrocycle Possessing Nitrogen Donors Assembled in the Cavity and Unique Water Clusters

“…Interestingly, in the crystal of [ 1 Ni 3 ], pentagonal prism clusters of water molecules were observed above and below the macrocyclic cavity. Many studies have been conducted on the structure and physical properties of molecular water clusters formed through the interaction with the surrounding molecules. − Although the pentagon as a basic unit is commonly found in water cluster structures, − the pentagonal prism cluster found in this study is a unique example, which is templated by the rigid planar macrocycle in which assembled nitrogen and oxygen atoms behave as hydrogen-bond acceptors.…”

Water adsorption in porous organic crystals of adamantane-bearing macrocycles

“…[11][12][13][14] Porous organic macrocycles have advantages in terms of handling and processability given their solubility in organic media, although crystalline solids composed of macrocycles, which are held together by weak noncovalent interactions between component units, are less stable than infinite solids of MOFs and COFs. [15][16][17][18] A number of inclusion crystals of macrocyclic compounds (e.g., resorcin [4]arenes, pyrogallol [4]arenes, and cyclotribenzoins) that can capture water molecules or clusters have been prepared by solution crystallization, [19][20][21][22] and crystal structures of single and oligomeric water clusters have been determined by X-ray analysis. However, there are only a handful of reports on water uptake by porous organic macrocycles.…”

“…15–18 A number of inclusion crystals of macrocyclic compounds ( e.g. , resorcin[4]arenes, pyrogallol[4]arenes, and cyclotribenzoins) that can capture water molecules or clusters have been prepared by solution crystallization, 19–22 and crystal structures of single and oligomeric water clusters have been determined by X-ray analysis. However, there are only a handful of reports on water uptake by porous organic macrocycles.…”