Although peptide amphiphiles have been explored as nanomaterials for different applications, nanostructures formed by hierarchical molecular assembly of sequencespecific peptidomimetics are much less developed. Such protein-like nanomaterials could enhance the current application of peptide-based amphiphiles by enriching the diversity of nanostructures, increasing in vivo stability for biomedical applications, and facilitating the understanding of biomacromolecular self-assembly. Herein we present a biomimetic γ-AApeptide amphiphile which forms nanorods. Our results demonstrate the capability of γ-AApeptide amphiphiles as a potential scaffold for the preparation of biomimetic and bioinspired nanostructures. The programmability and biocompatibility of γ-AApeptides could lead to novel nanomaterials for a wide variety of applications. ■ INTRODUCTIONMolecular self-assembly is ubiquitous and vitally important in nature. Through noncovalent interactions, monomeric units self-assemble together to construct complex systems with unique biological functions. 1 Examples of such hierarchical molecular assembly found in nature include self-assembly of lipids, proteins, and nucleic acids. 2 Research on molecular selfassembly is critical in nanotechnology because it sheds light on the understanding of molecular assembly mechanisms, the design of building blocks and monomeric units, and the construction of nanostructures and nanomaterials with desired functions. 3 There has been extensive interest in the development of peptide-based nanomaterials in the past decade, and their applications as nanomaterials, nanotechnology, and nanomedicines have been widely explored. 3 In these cases, polypeptides are used as monomer units to self-assemble into ordered nanostructures so as to develop novel functional nanobiomaterials that can mimic protein structures and functions. 4,5 This is because there are 20 natural amino acids that can be used as building blocks to construct an enormous number of peptides and proteins with a wide variety of lengths, hydrophobicity/hydrophilicity, and shapes, which leads to the formation of different nanostructures through self-assembly. 3 Among these peptide-based nanomaterials, peptide amphiphiles are mostly used to generate self-assembled nanostructures in aqueous environment. 6 Peptide amphiphiles consist of a hydrophilic peptide head with desired structures and functions and a hydrophobic tail. In aqueous solution, the hydrophobic tail, normally an alkyl chain, lipid, or hydrophobic peptide, induces the aggregation of peptide amphiphiles. Meanwhile, the hydrophilic heads, consisting of polar or charged amino acid residues, assemble into nanostructures through hydrophilic interactions with water and other molecules. So far, the nanostructures generated by peptide amphiphiles include nanotubes, nanorods, nanovesicles, micelles, nanobelts, and nanofibers. 7−13 However, despite tremendous effort in the development of peptide-based nanomaterials, non-natural oligomeric peptidomimetic-based nanomaterials hav...

This report details the synthesis and characterization of a series of Nb complexes and one tantalum complex supported by the [CF3–ONO]3– trianionic pincer-type ligand. Access to the trianionic Nb dichloride complex, [CF3–ONO]­NbCl2(OEt2) (3-Et 2 O), allows for the synthesis of Nb-dialkyl complexes, [CF3–ONO]­NbR2 (where R = benzyl (5), neopentylsilyl (6), neophyl (7)). The sterically encumbered Nb-neophyl complex (7) is thermally stable and fails to convert to the alkylidene even in the presence of donor ligands. Complex 7, however, promotes catalytic ring-opening metathesis polymerization (ROMP) of norbornene, suggesting the plausible intermediacy of a Nb-alkylidene. The corresponding Ta analogue, [CF3–ONO]­Ta­(CH2C­(CH3)2(C6H5))2 (9), requires dramatically higher temperatures to initiate ROMP and provides poor yields of polymer. Complexes 5 and 6 also promote ROMP of norbornene. Characterization of all new complexes includes multinuclear NMR spectroscopy and combustion analysis. For complex 7, characterization also includes solid-state structure elucidation via a single crystal X-ray diffraction experiment.

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