Modulating Charge Transfer through CyclicD,L‐α‐Peptide Self‐Assembly

Abstract

We describe a concise solid support-based synthetic method for the preparation of cyclic D,L α-peptides bearing 1,4,5,8-naphthalenetetracarboxylic diimide (NDI) side chains. Studies of the structural and photoluminescence properties of these molecules in solution show that the hydrogen bond directed self-assembly of the cyclic D,L α-peptide backbone promotes intermolecular NDI excimer formation. The efficiency of NDI charge transfer in the resulting supramolecular assemblies is shown to depend on the length of the linker between the NDI and the peptide backbone, the distal NDI substituent, and the number of NDIs incorporated in a given structure. The design rationale and synthetic strategies described here should provide a basic blueprint for a series of self-assembling cyclic D,L α-peptide nanotubes with interesting optical and electronic properties.

Janus cyclic peptide–polymer nanotubes

“…Probing the Janus character of CP-polymer NTs with shorter polymer chains (for example, PBA 36 -CP-PS 35 Figs S5 and S6). This was attributed to either the incompatibility of the polymer chains (11) or to incomplete cross-relaxation due to the dynamic nature of the short polymer chains (15).…”

“…The simplicity of this bottom-up approach together with the resultant uniformity and size of the self-assembled nanoscopic structures provides an attractive strategy, which favours applicability in the field of nanoscience and nanotechnology 5 . Among the different types of self-assembled architectures, nanotubular structures have gained considerable interest because of their suitability for various applications including nanomedicine 6,7 , (bio)sensing 8,9 , separation and recovery technologies 10 as well as nanoelectronics 11 . A distinct feature of tubular structures that is often absent from traditional self-organized supramolecular structures for example, micelles and vesicles, is the internal channel cavity, which in the case of self-assembled nanotubes (NTs) has a defined diameter that can provide a means for selective transport or molecular encapsulation properties.…”

The Design and Synthesis of Dansyl‐Containing Cyclic Pseudopeptides

“…As a part of a project directed towards the study of pseudopeptides containing pseudoproline moieties, [5] we wish to show here the synthesis of six cyclopeptides of different shape, all containing the -Oxd unit [-Oxd = trans- [ (4R,5S)-4-carboxy-5-methyloxazolidin-2-one unit] as an isoster for the -proline unit alternating with a generic -amino acid ( Figure 1). Indeed, cyclic ,-α-peptides are the archetypical members of a growing class of organic tubular macromolecular structures that have a plethora of promising potential applications, [6] so an efficient method for the preparation of these compounds is highly desirable. The introduction of the Oxd moiety can be very useful in the preparation of rigid cyclopeptides because, as we have demonstrated, the Oxd moiety imparts rigidity to a pseudopeptide chain due to the presence of the oxazolidin-2-one endocyclic carbonyls, which force the Oxd carbonyl groups exclusively into the trans conformation.…”

Challenges and breakthroughs in recent research on self-assembly

“…One representative example is nanotube formation by designer cyclic peptides prepared by Ghadiri and coworkers [126,127]. These self-assembled materials can operate as artificial membrane channels.…”