Supramolecular conducting nanowires from organogels.
Explore the source record for details and available documents.
Electric Conductivity↗
Biomedical subjects
David B Amabilino
Publications and source records attributed to David B Amabilino.
Chemical and constitutional influences in the self-assembly of functional supramolecular hydrogen-bonded nanoscopic fibres.
A new series of secondary amides bearing long alkyl chains with pi-electron-donor cores has been synthesized and characterised, and their self-assembly upon casting at surfaces has been studied. The different supramolecular assemblies of the materials have been visualized by using atomic force microscopy (AFM) and transmission electron microscopy (TEM). It is possible to obtain well-defined fibres of these aromatic core molecules as a result of the hydrogen bonds between the amide groups. Indeed, by altering the alkyl-chain lengths, constitutions, concentrations and solvent, it is possible to form different rodlike aggregates on graphite. Aggregate sizes with a lower limit of 6-8 nm width have been reached for different amide derivatives, while others show larger aggregates with rodlike morphologies which are several micrometers in length. For one compound that forms nanofibres, doping was performed by using a chemical oxidant, and the resulting layer on graphite was shown to exhibit metallic-like spectroscopy curves when probed with current-sensing AFM. This technique also revealed current maps of the surface of the molecular material. Fibre formation not only takes place on the graphite surface: nanometre scale rods have been imaged by using TEM on a grid after evaporation of solutions of the compounds in chloroform. Molecular modelling proves the importance of the hydrogen bonds in the generation of the fibres, and indicates that the constitution of the molecules is vital for the formation of the desired columnar stacks, results that are consistent with the images obtained by microscopic techniques. The results show the power of noncovalent bonds in self-assembly processes that can lead to electrically conducting nanoscale supramolecular wires.
Journal Article↗
Noncovalent control for bottom-up assembly of functional supramolecular wires.
Noncovalent bonds have been used to assemble stacks of pi-electron-rich moieties at a surface, generating a pathway for charge transport. The system is comprised of a tetrathiafulvalene (TTF) derivative incorporating two amide groups which fasten the relative orientations of the electroactive moieties in the supramolecular polymer that is formed at the surface of graphite in octanoic acid. Scanning tunneling microscopy (STM) combined with molecular mechanics calculations has been used to prove the structure of the wires, and theory, corroborated with STS experiments, predicts that they are promising superstructures for charge transport.
Journal Article↗
Chiral molecular tapes from novel tetra(thiafulvalene-crown-ether)-substituted phthalocyanine building blocks.
A tetra(thiafulvalene-crown-ether) phthalocyanine self-assembles into helical tapes nanometers wide and micrometers long. Formation of these scrolled molecular architectures is a first for phthalocyanine fibres and shows potential as a novel conducting material.
Journal Article↗
Reversible and irreversible conformational changes in poly(isocyanide)s: a remote stereoelectronic effect.
Poly(isocyanide)s prepared by diastereoselective polymerisation of two chiral monomers, which differ only in the presence of a nitro-group adjacent to the stereogenic group, exhibit long range chiral induction, but a surprising influence of a remote substituent on the conformation and stability of the secondary structure in the macromolecules.
Cyanides↗
A nanoscale view of supramolecular stereochemistry in self-assembled monolayers of enantiomers and racemates.
The effect that molecular chirality has on the formation of monolayer structures by pure enantiomers and their racemates at the liquid/solid interface has been investigated for two chiral compounds (1 and 2) which differ from each other by the presence or absence of an ester function in their respective molecular structures. 1 shows pseudoracemate formation when the achiral graphite support is exposed to a solution containing a racemate while 2 shows racemic conglomerate formation. This difference is rationalized in terms of the orientation of the pure enantiomers with respect to the graphite substrate and highlights the importance of molecular structure and its influence on balancing the interplay between molecular conformation and molecular packing on the surface. For 1, nonstoichiometric mixtures of both enantiomers have been investigated, and the results are discussed in the framework of the sergeant and soldiers principle. These results are important for the understanding and prediction of spontaneous resolution in monolayer systems.
Journal Article↗
Synthesis, separation, and isomer-dependent packing in two dimensions--detected by scanning tunnelling microscopy--of a TTF derivative.
The synthesis, isolation and STM imaging on graphite of the cis and trans isomers of a TTF reveal isomer-dependent packing, and constitutes a way to study the non-covalent interactions at play in these systems.
Journal Article↗
Spontaneous resolution and absolute configuration of a coordination polymer formed by MnII and a ferrocene-based bisnitronyl nitroxide radical.
Crystallisation of a ferrocenyl bis(nitronyl nitroxide) with manganese(II) bis(hexafluoroacetylacetonate) gives rise to spontaneous resolution of a coordination polymer formed by the two units creating seven sources of chirality.
Journal Article↗
New accelerated strategy for the synthesis of poly(ether ketone) dendrons.
A new AB(4)-type hypermonomer with four activated aromatic fluorines was prepared and converted to hyperbranched poly(ether ketones) by nucleophilic aromatic substitution of these fluorine atoms with phenolates. The preparation and application of the AB(4) hypermonomer for the accelerated synthesis of a family of poly(ether ketone) dendrons G2-G4 in good yield are described.
Journal Article↗
Spontaneous resolution under supramolecular control.
The spontaneous resolution of enantiomers is an intriguing and important phenomenon in a number of research areas. Non-covalent interactions can play a key role in the process which can now be observed not only in crystals, but in liquid crystals, self-assembled monolayers, self-assembled fibres, and supramolecules self-assembled in solution. The evidence gathered in all of these areas is important for explaining the transfer of chirality from molecule to bulk, and in particular the spontaneous resolution of enantiomers.
Journal Article↗