Hydrogen Bonding Guests Direct the Packing of a Small Organic Cage Molecule

Abstract

A small organic cage molecule (1) containing six nitrile groups was crystallized in the presence of a number of guests with hydrogen bond donor groups, and from different solvents. In total, eight crystal structures of 1 were obtained, six of which are guest-free and two of which are cocrystals. When the guest was resorcinol or pyrogallol, cocrystals did not form, but the presence of the guests directed formation of new crystalline phases that were not observed when the cage was crystallized alone. When the guest was hydroquinone or diaminobenzene, it was possible to isolate cocrystals where the guest hydrogen bonds to some of the nitrile groups of the cage.

Shape‐ and Size‐Tunable Synthesis of Covalent Organic Cages through Rh‐Catalyzed Regioselective [2+2+2] Cycloaddition

“…[28] The high chemical stability of the sp 3 atom-bridged arene cages enabled the introduction of functional groups by post-synthetic modification, [42][43][44][45] allowing the investigation as catalysts, [46] scaffolds for covalent/metalorganic frameworks (COFs/MOFs), [47,48] and porous organic crystals. [31,42,49,50] Although these methods have allowed the synthesis of various prismatic cages, the synthesis of a tetrahedral one has been limited to a thermodynamically controlled dynamic S N Ar reaction [51][52][53] that requires the slow addition of a substrate (2 hours). This reversible covalent bond formation made the resulting cage product chemically unstable.…”

“…In 2010, Wang and co‐workers also synthesized a prismatic aryl ether cage from phloroglucinol and cyanuric chloride by the stepwise S N Ar reactions (Figure 1d, bottom) [28] . The high chemical stability of the sp 3 atom‐bridged arene cages enabled the introduction of functional groups by post‐synthetic modification, [42–45] allowing the investigation as catalysts, [46] scaffolds for covalent/metal–organic frameworks (COFs/MOFs), [47, 48] and porous organic crystals [31, 42, 49, 50] . Although these methods have allowed the synthesis of various prismatic cages, the synthesis of a tetrahedral one has been limited to a thermodynamically controlled dynamic S N Ar reaction [51–53] that requires the slow addition of a substrate (2 hours).…”