Highly conductive ~40-nm-long molecular wires assembled by stepwise incorporation of metal centres (original) (raw)
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Towards Molecular Wires Based on Metal-Organic Frameworks
European Journal of Inorganic Chemistry, 2009
The formation of one-dimensional structures on nanoscale is one of the main goals of modern nanotechnology. The aim of these efforts is to find conductive long molecules that could serve as molecular wires in nanocircuits. In recent years, electrical conductivity in several organic and metal-organic systems has been studied to this end. In principle, DNA is one of the most attractive molecules for molecular wire owing to its well-known self-assembly chemistry and controllable structural diversity. However, the ability of DNA to conduct electricity is still controversial. In principle, binding of metal ions to organic molecules seems to be a suitable method for improving conductivity. Therefore, some studies were carried out with the so-called M-DNA as an alternative to increase conductivity on DNA. We have selected the 1Dcoordination polymer [Cd(6-MP-) 2 ] n (6-MP-= 6-mercaptopurinate) as a feasible structural model that is suitable for pro
Design of novel molecular wires for realizing long-distance electron transfer
1997
Novel heteroarene oligomers, consisting of two pyridinium groups, linked by thiophene units of variable length, "tlfienovio~eas", are described as promising candidates for molecular wires. Two representative thienoviologens were coaled by adsorption from mieromolar concentrations in ethanol onto octadecylmereaptan (ODM)-coated gold electrodes and induced a gradual restora~ of the electrochemistry with hexacyanoferrate as a function of molecular wire concentration. Glucose oxidase and choline oxidase showed strong adsorption to these conductive layers, but showed striking differences in adsorption to the different thienoviologen layers. The measurements support the hypothesis that the molecules are incorporated in the ODM layer in a different fashion. Also the complex formation of an engineered azurin redox protein with water-soluble pyridyl ligands is pre~nted in relation to a possible application of the thienoviologens as conductive spacers, in which the contact with the redox protein is achieved via complex formation with a free pyrk~ae nitrogen.
Single-molecule electrical studies on a 7 nm long molecular wire
Chemical Communications, 2006
A self-assembled arylene-ethynylene molecular wire with a rigid 7 nm long backbone exhibits symmetrical current-voltage (I-V) characteristics and a single-molecule current of 0.35 ¡ 0.05 nA at 0.3 V; these data are supported by theoretical calculations.
High Electrical Conductivity of Single Metal-Organic Chains
Advanced materials (Deerfield Beach, Fla.), 2018
Molecular wires are essential components for future nanoscale electronics. However, the preparation of individual long conductive molecules is still a challenge. MMX metal-organic polymers are quasi-1D sequences of single halide atoms (X) bridging subunits with two metal ions (MM) connected by organic ligands. They are excellent electrical conductors as bulk macroscopic crystals and as nanoribbons. However, according to theoretical calculations, the electrical conductance found in the experiments should be even higher. Here, a novel and simple drop-casting procedure to isolate bundles of few to single MMX chains is demonstrated. Furthermore, an exponential dependence of the electrical resistance of one or two MMX chains as a function of their length that does not agree with predictions based on their theoretical band structure is reported. This dependence is attributed to strong Anderson localization originated by structural defects. Theoretical modeling confirms that the current is...
Nanotechnology, 2007
This article describes arylene-ethynylene molecular wires with 7 nm long backbones and thiolated termini. Cyclic voltammetric studies in solution reveal that the reduction waves of the fluorene, 9-[(4-pyridyl)methylene]fluorene and 9-[di(4-pyridyl)methylene]fluorene units which are embedded in the conjugated π -systems endow these wires with n-doping characteristics. An x-ray crystal structure investigation of 2,7-diiodo-9-[bis(4-pyridinium)methylene]fluorene bis(tetrafluoroborate) 8 established that protonation occurs on both nitrogens of this unit. Self-assembled monolayers of the 7 nm wire 2 on gold substrates exhibit symmetrical current-voltage (I -V ) characteristics when contacted by a gold scanning transmission microscope (STM) tip. The dipyridyl functionality of 2 served to obtain a rectifying junction in which the diprotonated cationic wire is the electron accepting component in combination with an adjacent anionic phthalocyanine as the electron-donating layer. This ionic Au-2H 2+ 2 [CuPc(SO − 3 ) 4 (Na + ) n ] 2/(4−n) bilayer assembly exhibits rectification with current ratios of 15-50 at ±1 V. This dramatic change in I -V characteristics upon simple chemical manipulation proves that the conductivity is a property of the wire molecules 2 in the junction. Ab initio calculations suggest that the molecular wires possess useful structural features which allow the conductance of the molecule to be altered by changing the properties of the side groups attached to the fluorene units.
Atomically Wired Molecular Junctions: Connecting a Single Organic Molecule by Chains of Metal Atoms
Using a break junction technique, we find a clear signature for the formation of conducting hybrid junctions composed of a single organic molecule (benzene, naphthalene, or anthracene) connected to chains of platinum atoms. The hybrid junctions exhibit metallic-like conductance (∼0.1−1G 0 ), which is rather insensitive to further elongation by additional atoms. At low bias voltage the hybrid junctions can be elongated significantly beyond the length of the bare atomic chains. Ab initio calculations reveal that benzene based hybrid junctions have a significant binding energy and high structural flexibility that may contribute to the survival of the hybrid junction during the elongation process. The fabrication of hybrid junctions opens the way for combining the different properties of atomic chains and organic molecules to realize a new class of atomic scale interfaces.
Adventures in molecular electronics: how to attach wires to molecules
Applied Surface Science, 2003
Films of both methoxy-terminated alkanethiols and a molecular wire candidate on Au{1 1 1} substrates were exposed to a variety of transition and alkali earth metals (Al, Au, Ag, Ca, Cr, Fe, Cu, Mg, Ti). The results show that aggressively reacting metals, such as Ti, destroy the organic monolayer and metals of intermediate reactivity, e.g. Cu, react at the termini and also penetrate the monolayer and react with the substrate. The results of these investigations provide a basis by which future construction of molecular devices based on desired chemical reactivity may proceed.
Electrical transport measurements on self-assembled organic molecular wires
The Journal of Chemical Physics, 2006
The electrical properties of supermolecular assemblies of oligo͑p-phenylene vinylene͒ were studied. These materials self-assemble into well-defined cylindrical structures in solution with lengths in the range of 100 nm-10 m and diameters between 5 and 200 nm. Atomic force microscopy showed that by adjusting the concentration, either individual molecular wires or a dense film could be deposited. The molecular wires showed poor electrical conduction. Several tests were performed that show that it was the molecular wires themselves, not the contacts, that limit the conductivity.