Supramolecular Assemblies Constructed from Cucurbit[8]uril and N‐Alkyl Carboxymethylbenzotriazole through Host‐Guest Interactions

Abstract

Different supramolecular self‐assembly between 1‐dodecyl‐3‐carboxymethylbenzotriazole (Lc12), 1‐octyl‐3‐carboxymethylbenzotriazole (Lc8) and 1‐butyl‐3‐carboxymethylbenzotriazole (Lc4) in the solid state and in aqueous solution has been investigated. For Lc12@CB[8] system, 1 : 1 host‐guest complexes were formed in aqueous solution and 2 : 2 host‐guest complexes were formed in the solid state, and the dodecyl chains adopted contorted conformations when bound to CB[8] molecules. For Lc8@CB[8] system, 1 : 1 host‐guest complexes were formed both in aqueous solution and in solid state, and the alkyl chain and benzotriazole moiety of guest Lc8 were both squeezed into the cavity of the CB[8]. The Lc4@CB[8] system was similar to Lc8@CB[8], 1 : 1 host‐guest complexes were formed in aqueous solution, the alkyl chain and benzotriazole moiety of guest Lc4 were encapsulated into the cavity of the CB[8]. Isothermal titrations in water afforded high apparent association constants for complexes Lc12@CB[8], Lc8@CB[8]and Lc4@CB[8].

Methyl Hexadecyl Viologen Inclusion in Cucurbit[8]uril: Coexistence of Three Host–Guest Complexes with Different Stoichiometry in a Highly Hydrated Crystal

“…A similar 2:2 complex stabilized by π•••π interactions between the aromatic moieties of adjacent guests was observed in the crystal structure of CB [8] with 1-dodecyl-3-carboxymethylbenzotriazole. 25 In that case, 1:1 host−guest complexes were formed in aqueous solution, while 2:2 host−guest complexes were observed in the solid state by π•••π dimerization of partially exposed benzotriazole moieties. The conformation of the alkyl chain and the deformation of the CB [8] cavity in the present 2:2 complex are similar to that observed in the 3:2 complex.…”

“…In fact, the pyridinium ions are sandwiched between the oxygen portals with negative electrostatic potential (Figure ). A similar 2:2 complex stabilized by π···π interactions between the aromatic moieties of adjacent guests was observed in the crystal structure of CB­[8] with 1-dodecyl-3-carboxymethylbenzotriazole . In that case, 1:1 host–guest complexes were formed in aqueous solution, while 2:2 host–guest complexes were observed in the solid state by π···π dimerization of partially exposed benzotriazole moieties.…”