Cucurbit[8]uril‐Mediated Redox‐Controlled Self‐Assembly of Viologen‐Containing Dendrimers

Abstract

The dimerization of dendrimers that contain a single 4,4′‐bipyridinium (viologen) unit, upon one‐electron reduction, is strongly enhanced by the presence of the host cucurbit[8]uril. This behavior is attributed to the formation of a stable inclusion complex between the host and two π‐stacked viologen radical‐cation guests—the one‐electron‐reduced form of viologen (see scheme).

Effects of sequence context on the binding of tryptophan-containing peptides by the cucurbit[8]uril–methyl viologen complex

“…Compared to other cucurbit[n]urils, Q8 has been studied extensively for its ability to bind two guests simultaneously in aqueous solution (20)(21)(22)(23)(24)(25)(26)(27)(28)(29). Much of our work with Q8 has focused on the molecular recognition of peptides (30)(31)(32)(33)(34)(35)(36).…”

Viologens as Components of Supramolecular Structures

“…The CB8-induced dimerization of dendrimeric viologens (40a, 41a) and (42b) has been reported [22]. It was found that the radical cation MV •+ is more strongly stabilized by CB8 than the dicationic MV 2+ ; the association of two dendrimers proceeds via dimerization of their viologen radical cations inside the CB8 cavity affording 44.…”

“…One should also mention here the covalently linked donor-acceptor self-complexing compounds (22), investigated in the aspect of their function as simple molecular machines [14]. The -donating arm may intra-molecularly enter into the cyclophane (14) cavity due to stabilization by noncovalent bonding interactions.…”

Molecular Encapsulation of Redox‐Active Guests

“…14 For instance, we have used it for the redox-controlled self-assembly of viologen-containing dendrimers. 42,43 In 2003, we reported that both ferrocene and ferrocenium form inclusion complexes with CB7. 44 The oxidized form is slightly preferred as the guest, but the selectivity is very moderate.…”