Oligomeric Cucurbituril Complexes: from Peculiar Assemblies to Emerging Applications

Abstract

Proteins are an endless source of inspiration. By carefully tuning the amino‐acid sequence of proteins, nature made them evolve from primary to quaternary structures, a property specific to protein oligomers and often crucial to accomplish their function. On the other hand, the synthetic macrocycles cucurbiturils (CBs) have shown outstanding recognition properties in water, and a growing number of (host)n:(guest)n supramolecular polymers involving CBs have been reported. However, the burgeoning field of discrete (n:n) host:guest oligomers has just started to attract attention. While 2:2 complexes are the major oligomers, 3:3 and up to 6:6 oligomers have been described, some associated with emerging applications, specific to the (n:n) arrangements. Design rules to target (n:n) host:guest oligomers are proposed toward new advanced host:guest systems.

Solvent-controlled formation of alkali and alkali-earth-secured cucurbituril/guest trimers

“…Inspired by the work of Bardelang and coworkers, 18–22 we then suspected that aggregation might take place and result in the formation of larger clusters of complex CB[7]· 1 in DMSO. Bardelang and coworkers showed that in the presence of sodium cations (≥5.0 mM), CB[8]-bound nitroxide radicals undergo trimerization in D 2 O; they also observed a small amount of aggregation in the absence of added sodium, and attribute it to the trimer without its sodium core cation.…”

Cucurbituril Based Luminescent Materials in Aqueous Media and Solid State

“…However, CB[8] provides options to produce n:n oligomeric complexes. For example, complexes with host : CB[8] stoichiometry ranging from 2 : 2 to 6 : 6 have been reported [18] . In the next few sections, selected examples on small (1 : 1) and oligomeric luminescent complexes of CB[7] and CB[8] will be discussed.…”

Fluorescent Paracyclophanes: Unveiling Ultra‐Strong Binding with Cucurbit[8]uril in Aqueous Environments

“…[16] An important contribution to the supramolecular-materials field was the development of functionalizable cucurbit[n]urils, particularly CB6 and CB7, which allowed their use to construct sensing assays, [17][18][19] to assemble supramolecular systems, [20,21] their incorporation in polymeric systems such as hydrogels, [22][23][24] and their use for surface labeling and protein sequestering applications. [25][26][27][28][29][30][31][32][33] More recently, also CB8-based functional molecules [34] and materials based on CB8 [35][36][37] have emerged after more reliable methods for their chemical mono-functionalization were established. [38] Compared to the number of known high-affinity guests for CB7, the variety of suitable compounds to form ultra-strong inclusion complexes with CB8 is much more limited, with Alzheimer's drug memantine being the most commonly used compound.…”

“…An important contribution to the supramolecular‐materials field was the development of functionalizable cucurbit[ n ]urils, particularly CB6 and CB7, which allowed their use to construct sensing assays, [17–19] to assemble supramolecular systems, [20,21] their incorporation in polymeric systems such as hydrogels, [22–24] and their use for surface labeling and protein sequestering applications [25–33] . More recently, also CB8‐based functional molecules [34] and materials based on CB8 [35–37] have emerged after more reliable methods for their chemical mono‐functionalization were established [38] .…”