Solvent-Modulated Formation of “Pac-man” and Capsular Host–Guest Bilayers from a Dicationic Ionic Liquid and C-Butylpyrogallol[4]arene

Abstract

The pyrogallol [4]arenes have been shown to act as versatile host macrocycles for a wide variety of guest molecules, including the imidazolium-based cations of ionic liquids. This report demonstrates the use of alkyl-linked geminal dications in the design of bilayers comprising dimeric host−guest complexes. The pivotal role of solvent choice in controlling the resultant solid-state structure is particularly highlighted. The synthesis and single-crystal X-ray diffraction structures of two dimeric host−guest cocrystals generated by the use of different solvents while employing identical host and guest species are presented to illustrate this point. In one solvent, a "Pac-man"-type dimeric host−guest complex is assembled into bilayer galleries. With a switch to an alternate crystallization solvent, a bilayer-type structure in which each layer is composed of alternating complexes of a capsule and two "offset dimers" is instead constructed.

Unexpected narcissistic self-sorting at molecular and supramolecular levels in racemic chiral calixsalens

“…This motif is known as the Pac-man dimer, and was originally observed by Atwood et al in the inclusion compound of C-butylpyrogallolij4]arene. 24 Also, the alternating arrangement of both homo-and heterochiral motifs in pillars is strongly inclined, as shown in Fig. 4b.…”

Application of Cocrystallization for the Separation of C-Ethylresorcin[6]arene from C-Ethylresoricn[4]arene

“…Macrocyclic compounds such as C -alkylresorcin­[4]­arenes (4-RsCn) and C -alkylpyrogallol­[4]­arenes (4-PgCn) are useful for construction of supramolecular organic frameworks where the approach of cocrystallization is often used. − 4-RsCn and 4-PgCn have unique bowl-shaped structures in which the upper rim of the bowl has 8 or 12 hydroxyl groups, respectively, while the lower rim contains four C -alkyl chains. These structural features of 4-RsCn and 4-PgCn offer a variety of intermolecular interactions such as hydrogen bonds through the hydroxyl groups, π–π interactions through the aromatic resorcinol or pyrogallol, H−π interactions through π-electron cloud of the 4-RsCn/4-PgCn bowl, and van der Waals forces through the C -alkyl chains. − Usually, crystallization of 4-RsCn or 4-PgCn entities yields bilayer, hexameric, or tubular arrangements of these macrocycles in the crystalline solid state. , However, cocrystallization of 4-RsCn and 4-PgCn with organic molecules such as 4,4′-bipyridine (bpy) results in a variety of framework architectures ranging from extended bilayers, wave-like arrangements, skewed bricks, extended capsules, and extended 1D to 2D frameworks. ,− Cocrystallization of 4-RsCn/4-PgCn with various small molecules is also employed to investigate host–guest interactions, and gas sorption ability of framework materials. ,− However, higher homologues of 4-RsCn/4-PgCn such as C -alkylresorcin­[5]­arenes and C -alkyresorcin­[6]­arenes (Scheme ) have not been explored much for construction of supramolecular frameworks since the synthesis and separation of these higher homologues are difficult .…”

Endo vs Exo Bowl: Complexation of Xanthone by Pyrogallol[4]arenes

“…Along with their ability to participate in hydrogen bonding, pyrogallol[4]arenes are useful for cocrystallizations because of their capability to form various supramolecular structures such as nanocapsules and nanotube assemblies . Pyrogallol[4]arenes are also ideal for cocrystallization due to their capacity to act as hosts for small inorganic molecules, drug molecules, and ionic liquids. − …”