Investigation of self-organization behavior of organic (semi)-conductors became very important recently, since their physical properties and performance in organic electronic devices strongly depend on ordering effects, on both molecular and nanoscale levels. [1] In this respect, bioinspired functionalization of conjugated systems might greatly enhance the diversity of electronically interesting assemblies, and potentially allow for the rational design of hierarchically ordered nanostructures.[2] Thus, from possible hybrids of conjugated backbones, the combination of oligo-or polythiophenes with biomolecules, such as nucleotides, [3] carbohydrates, [4] or peptides, [5] are interesting. Particularly, the latter appears to be attractive, because interplay between different intermolecular forces in the peptide and oligothiophene segments results in competing self-assembly motifs. Hence, very specific organization properties can be expected. Whereas thiophene-based materials typically form well-organized 2D lamellar superstructures due to van der Waals interactions of alkyl side chains, and stack into the third dimension via p-p interactions, [6] secondary structures of peptides, preferentially bsheets or a-helices, are governed by stronger and directed hydrogen-bond formation.[7] The high tendency of peptides to adopt well-defined secondary-structure motifs has been exploited recently to guide self-organization of a broad range of synthetic polymers.[8] Attention has mainly been devoted to the b-sheet motif, leading to anisotropic fibrillar or fiber-like structures. [9] However, other highly interesting assembly motifs, for example the coiled-coil motif, were exploited, resulting in distinct nanoobjects by the lateral assembly of amphiphilic a-helices. [10] We recently presented the first conjugate between a regioregularly alkylated quaterthiophene and a pentapeptide consisting of a silk-inspired sequence of alanine-glycine repeats, which is known to adopt b-sheet structures.[5a] Unexpected and novel 3D nanostructures were found, suggesting that short peptide sequences may indeed influence the nanoscale structure, and ultimately, properties of organic semiconducting materials.The versatility of this class of hybrid oligo-/polymers is certainly not exploited, considering the diversity of both the conjugated oligo-/polymer platforms and the bioorganic segments. It becomes increasingly evident that such materials will envelop by far more structural and functional space as, for example, common AB-block copolymer systems.[11]Here, we present the synthesis and self-organization behavior of a symmetrically substituted A-B-A-type bioinspired semiconductor, quaterthiophene-peptide hybrid 8 (Scheme 1b), by combining a central quaterthiophene segment (B) with two peptide-poly(ethylene oxide) bioconjugates (A).As outlined in Scheme 1, the oligothiophene segment was substituted on both sides with an amino acid sequence Gly-(ThrVal) 3 -Gly-aPhe-Gly (Scheme 1, structure 2), with Gly ¼ glycine, Val ¼ valine, Thr ¼ threonine, ...

We report herein the synthesis of a novel type of hybrid compound that consists of a poly(ethylene oxide) (PEO) functionalized β-sheet peptide sequence covalently linked to an alkylated quaterthiophene moiety. Compounds of this class are highly promising for technological applications because their self-assembly and stimuli-responsive behavior, which is mainly caused by the peptide moieties, combined with the potential semiconducting properties of oligothiophenes provides unprecedented opportunities for the design of advanced materials at the nanoscale in such areas as, for example, organic electronics and sensor design for chemical and biomedical applications. The compound presented herein is experimentally shown to form stable fibrillar aggregates that are visualized by both transmission electron and atomic force microscopy. We developed a theoretical methodology to study the possible intermolecular arrangements and their characteristic features with the help of all-atom MD simulations, while simultaneously incorporating available experimental data into the model. Large-scale atomistic simulations of several fibrillar aggregates with different molecular arrangements were performed. The results of the simulations are compared with experimental data, which leads to the proposition of a likely model for the arrangement of the individual molecules within the observed aggregates.

Within the present work, synthesis and properties of three stereoisomeric hybrid materials consisting of a πconjugated oligothiophene backbone and a single amino acid (proline), which is attached by click chemistry, are described. The hybrids were in particular investigated regarding their self-assembling behavior in solution. From optical investigations, including circular dichroism spectroscopy, the formation of chiral suprastructures could be deduced and correlated with the stereochemistry of the proline residue. In addition, an elaborate theoretical model of the compounds' self-assembly into suprastructures was developed on the basis of the experimental findings.

SummaryIn this minireview, we survey recent advances in the synthesis, characterization, and modeling of new oligothiophene–oligopeptide hybrids capable of forming nanostructured fibrillar aggregates in solution and on solid substrates. Compounds of this class are promising for applications because their self-assembly and stimuli-responsive properties, provided by the peptide moieties combined with the semiconducting properties of the thiophene blocks, can result in novel opportunities for the design of advanced smart materials. These bio-inspired molecular hybrids are experimentally shown to form stable fibrils as visualized by AFM and TEM. While the experimental evidence alone is not sufficient to reveal the exact molecular organization of the fibrils, theoretical approaches based on quantum chemistry calculations and large-scale atomistic molecular dynamics simulations are attempted in an effort to reveal the structure of the fibrils at the nanoscale. Based on the combined theoretical and experimental analysis, the most likely models of fibril formation and aggregation are suggested.

A fi rst representative of a novel class of bioinspired materials, a fully symmetric hybrid between an oligothiophene and a ␤-sheet peptide, is introduced in work by Peter Bäuerle and co-workers on p. 1562. The conjugate can be synthesized via click-chemistry and employs a switch-peptide segment to gain control over the self-assembly motif of the peptide part.

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