Dual Self-Sorting by Cucurbit[8]uril To Transform a Mixed Micelle to Vesicle

Abstract

A systematic study on the cucurbit[8]uril (CB[8]) assisted transformation of a mixed micellar system of CTAB and a viologen surfactant to vesicles is depicted. The micelle to vesicle transformation is assisted by a charge transfer complex mediated ternary complexation between the viologen group of the surfactant, CB[8], and 2,6-dihydroxynaphthalene. In the presence of CB[8], both the surfactants formed U-shaped binary inclusion complexes inside the CB[8] cavity, and no selective binding is observed. Upon addition of DHN, CB[8] showed two different self-sorting mechanisms. The U-shaped binary complex with CTAB breaks down, and CB[8] moves toward the viologen headgroup of the other surfactant to form a stable ternary complex. In the case of the viologen surfactant, CB[8] moved toward the headgroup leaving the hydrophobic tail free in order to form the ternary complex. The mechanistic detail of this micelle to vesicle transformation is revealed through methodical studies using (1)H and DOSY NMR, ESI-MS, ITC, and other instrumental techniques.

Supramolecular Chemistry of Cucurbiturils: Tuning Cooperativity with Multiple Noncovalent Interactions from Positive to Negative

“…[56][57][58][59] We wondered if it would be possible to design an advanced self-sorting system by adjusting the cooperativity in complexation for the benzylamine guests with CB [8]. Based on the thermodynamic stability of 1:1 complexes arising from negative cooperativity, and 2:1 complexes stemming from positive cooperativity, we envisioned that a mixture of guests that distinctly resulted in either 1:1 or 2:1 complexation with CB [8] may exhibit self-sorting.…”

Reversible deformation–formation of a multistimuli responsive vesicle by a supramolecular peptide amphiphile

“…Upon addition of Triton X-100 (a well-known vesicle destroyer) a sudden enhancement of the fluorescence intensity confirms the formation of vesicles by Trp-HDEV@CB [8] ( Figure 2). 39,41 Earlier studies show that in absence of any second guest, CB [8] forms a binary complex at the tail of HDEV. It is worth mentioning that ITC experiments with such binary complexes of CB [8] and amphiphilic molecules like HDEV could not provide any conclusive results as was also observed earlier.…”

“…32 Importantly, the ternary complex, Trp-HDEV@CB [8] transformed the solutions into spherical nano-aggregates as seen from the FESEM and TEM images ( Figure 2). [37][38][39][40][41] In order to confirm the formation of vesicles, we have entrapped a water soluble dye, CF, inside these nano-aggregates and followed the release of the encapsulated dye through enhancement of fluorescence intensity. [37][38][39][40][41] In order to confirm the formation of vesicles, we have entrapped a water soluble dye, CF, inside these nano-aggregates and followed the release of the encapsulated dye through enhancement of fluorescence intensity.…”

“…A slow release of the dye was observed. 39 Under such circumstances, it is a common practice to assume that the binding constants for the amphiphiles (eg. In order to investigate the failure of Phe and Tyr to form ternary complexes with HDEV@CB [8], we have measured the association constants for all these amino acids with DEV@CB [8] binary complexes through isothermal titration calorimetry (ITC).…”

“…Since the molecules are adhered together through multiple weak interactions, appropriate stimulus can be used to dis-assemble them easily. 38,39 Scheme 1. CB [8] is a macrocyclic synthetic host capable of accommodating two guests inside its hydrophobic cavity simultaneously and hence acts as a "supramolecular handcuff".…”