Sequence-Specific Self-Assembly of Positive and Negative Monomers with Cucurbit[8]uril Linkers

Abstract

The self-assembly into dynamic oligomers of Cucurbit[8]uril (CB[8]), a positive ditopic Ir(III) bis-terpyridine complex, and a negative ditopic Fe(II) bis-terpyridine complex flanked by four butyrate side chains was assessed to answer a seemingly straightforward question: does CB[8] adopt a social self-sorting pattern by encapsulating both positive and negative units into a heteroternary complex? We showed that this is indeed the case, with CB[8] linking a positive Ir unit to a neighboring negative Fe unit whenever possible. Furthermore, the solubility of the dynamic oligomers was significantly affected by their sequence; upon addition of 0.6-1.2 equiv of positive Ir oligomer to its negative Fe counterpart, the predominant assembly present in solution was a mixed oligomer with a (Fe-Ir-Ir-) sequence. Weak interactions between the negative butyrate side chains and the partially positive outer wall of CB[7] were also identified by two-dimensional nuclear magnetic resonance techniques, and resulted in a negative p K shift (0.10 p K unit) for the terminal carboxylic groups.

A Visible–Near‐Infrared Light‐Responsive Host–Guest Pair with Nanomolar Affinity in Water

“…CBn can be employed in numerous applications that are based on the extraordinary high affinity displayed by these macrocycles. Examples include recognition, self‐assembly and isolation of biomolecules, noncovalent functionalization of biopharmaceuticals, bioimaging and supramolecular materials such as polymers, microcapsules, and supramolecular organic frameworks …”

“…Examples include recognition, self-assembly andi solationo fb iomolecules, noncovalent functionalization of biopharmaceuticals, bioimaging and supramolecular materials such as polymers, microcapsules, and supramolecular organic frameworks. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] Akey feature of supramolecular systems relies on the reversible nature of noncovalent bonds,a llowing control of association processes using externals timuli. Light is recognized as a superior stimulusf or many applications because it allows for remote spatiotemporal control, it is orthogonal to other stimuli, and additional reagents are not required.…”

Oligomeric Cucurbituril Complexes: from Peculiar Assemblies to Emerging Applications

“…In 2014, [101] Masson and co-workers discovered that linear homo-oligomers of various length could be formed by mixing Fe complexes or Ir complexes with CB [8].Bymixing the two metal complexes with CB [8],h etero-oligomers were observed with an alternated sequence of Fe and Ir complexes suggesting social self-sorting.T his work was extended in 2018 [102] with different complexes of Fe and Ir affording again linear homo-oligomers and hetero-oligomers characterized by ar epetitive sequence of Fe-Ir-Ir complexes.T hese oligomers could also be considered as oligo-(2:2) and oligo-(3:3) complexes,r espectively.I na nother frontier system, Urbach and co-workers have described partially covalent analogues of a2:4 and a3:6 host:guest system that can be seen as cyclic 2:2and bicyclic3:2 complexes,respectively. [103] Using the double recognition of phenylalanine by CB [8], [27] Liu and colleagues designed doubly FGG-tagged proteins that were circularly oligomerized thanks to CB [8].…”

Guest Exchange by a Partial Energy Ratchet in Water

“…[29] In 2000, the chemistry of the synthetic macrocycle cucurbit [6]uril dramatically expanded after the reports of lower and higher size homologues. [30,31] Cucurbit[n]urils (CB-[n]) [32][33][34][35][36] have since then been used in ap lethora of applications in water, [37][38][39][40][41][42] including molecular machines [43][44][45] or more recently systems working away from equilibrium. [46][47][48] In about 20 years,k ey results were obtained by the teams of Isaacs,K im, Kaifer and others illustrating the relevance of using CB[n]for self-sorting, [49][50][51][52] stimuli-responsive systems, [42,45,[53][54][55] or for kinetic versus thermodynamic control.…”