Self-assembly of supramolecular triarylamine nanowires in mesoporous silica and biocompatible electrodes thereof

Triarylamine-Based Supramolecular Polymers: Structures, Dynamics, and Functions

Triarylamine molecules and triarylamine-based covalent polymers have been extensively investigated for more than 60 years in academics and industry because of their intriguing electronic and optical characteristics. However, despite the profusion of studies made on these derivatives, only very recently have the first examples of supramolecular polymers based on the triarylamine motif been described in the literature. Specifically, our research group has shown that, by adding supplementary hydrogen bonding moieties such as amide functions in their periphery, it becomes possible to tightly pack triarylamine molecules in columnar supramolecular stacks presenting a collinear arrangement of their central nitrogen atoms. These supramolecular polymers can self-assemble into various soft hierarchical structures such as helical fibers, nanorods, nanospheres, and nanoribbons in the sol and in the gel states, into liquid-crystalline mesophases, and into highly organized supramolecular frameworks and single crystals thereof. Interestingly, the associated supramolecular polymerization mechanism involves a nucleation step of high activation energy, which requires the flattening of the triarylamine core. Because of this singularity and although dependent on the precise chemical nature of the building blocks, it has been demonstrated that their supramolecular polymerization can be triggered by original tools, such as light irradiation or electrochemistry, and that it can display autocatalytic growth behaviors, remarkably strong amplifications of chirality, and complex and competing thermodynamic and kinetic self-assembly pathways. Further, from a functional point of view, it has been highlighted that a partial oxidation of the triarylamine molecules results in an enhanced through-space delocalization of the charge carriers along the π-π stacked supramolecular polymers, a feature that confers to these nanowires exceptional transport properties. Upon increasing the charge carrier concentration, the electronic nature of these soft materials can be switched from semiconducting to metallic behavior, and the presence of highly delocalized unpaired electrons in supramolecular polaronic band structures has been further exploited to implement plasmonic properties within subwavelength organic interconnects and microscopic optical waveguides. Finally, by making use of the unusual dynamics and functions of triarylamine-based nanostructures, it becomes possible to precisely address their self-construction within confined environments or within nano- and micrometer scale devices. This has been demonstrated for instance between nanoparticles and between electrodes, inside inorganic nanopores, and inside phospholipid bilayers, as well as at the liquid-liquid interface. Such a meeting point between bottom-up and top-down technologies is of high interest to envision further developments and applications for this entirely new class of supramolecular polymers, which combine a unique relationship between their structures, their dynamics, and their subsequent emerging functional properties.

3D supramolecular self-assembly of [60]fullerene hexaadducts decorated with triarylamine molecules

A clickable fullerene hexa-adduct scaffold has been functionalized with twelve triarylamine subunits. The light-triggered self-assembly of this molecular unit leads to 3D honeycomb-like structures with inner pores of around 10 nm diameter. Multiple grafting of triarylamine subunits onto a hard-core C₆₀ unit increases the dimensionality of the self-assembly process by reticulating the 1D nanowires typically obtained from the supramolecular polymerization of triarylamine monomers.

Long-Range Energy Transport via Plasmonic Propagation in a Supramolecular Organic Waveguide

Energy transport in organic materials is dependent on the coherent migration of optically induced excited states. For instance, in active organic waveguides, the tight packing of dye molecules allows delocalization of excitons over a distance generally limited to at most several hundred nanometers. Here, we demonstrate an alternative mechanism of energy transport in a triarylamine-based supramolecular organic waveguide that is plasmonic in nature and results in coherent energy propagation superior to 10 μm. The optical, electric, and magnetic properties of the doped material support the presence of metallic electrons that couple with and transport incident light. These results show that organic metals constitute a novel class of materials with efficient energy transport and are of potential interest for optoelectronics, plasmonics, and artificial light-energy harvesting systems.