Electron Conducting Devices. Molecular Wires

Among the various devices and components performing molecular-scale electronic functions that may be imagined, a crucial one is a molecular wire, which might operate as a connector permitting electron flow to occur between the different elements of a molecular electronic system. 

the caroviologen approach does produce functional molecular wires that effect electron conduction in a supramolecular-scale system. Incorporation into black lipid bilayer membranes (BLM) should allow further investigations of the electron-transfer properties of these caroviologens and positive preliminary results have been obtained [8.145a]. A theoretical investigation of electron conduction in molecular wires has been made [8.145b]. 

Since caroviologens are rather fragile compounds, they can be protected from the environment by inclusion into polyanionic derivatives of (J-cyclodextrin in a rotaxane fashion 102 [8.156]. Also, in the design of molecular devices, it may be desirable to introduce some extent of redundancy in order to reduce the risk of device failure. This is the case in the tris-carotenoid macrobicycle 103 that represents a sort of triple-threated molecular cable whose crystal structure 104 has been determined. It forms a dinuclear Cu(i) complex 105 in which the bound ions introduce a positive charge at each of the species, a feature of potential interest for transmembrane inclusion [8.157]. 

The development of electronic circuity will require the relative positioning of components. This has been investigated, for instance, through orthogonal connection of two oligothiophenes via spiro junctions (e.g., 106) [8.158, 8.159]. Electron 

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Many other opportunities exist due to the enormous flexibility of the preparative method, and the ability to incorporate many different species. Very recently, a great deal of work has been published concerning methods of producing these materials with specific physical forms, such as spheres, discs and fibres. Such possibilities will pave the way to new application areas such as molecular wires, where the silica fibre acts as an insulator, and the inside of the pore is filled with a metal or indeed a conducting polymer, such that nanoscale wires and electronic devices can be fabricated. Initial work on the production of highly porous electrodes has already been successfully carried out, and the extension to uni-directional bundles of wires will no doubt soon follow. 

Regarding the correct terminology, there are several references and examples of the term molecular wire . In some cases, it describes a system with a very specific behavior. In others, it simply refers to the structural features of the molecule under consideration. Thus, finding a clear definition is a rather difficult task. In 1998 an attempt was made by Emberly and Kirczenow [1] and a molecular wire has been defined as a molecule between two reservoirs of electrons . Nitzan and Ratner, on the other hand, called it a molecule that conducts electrical current between two electrodes [2], Most appropriate with respect to the topic of this thesis, we should stick to a rather restricted definition by Wasielewski, which classifies a molecular wire as a device that conducts in a regime, wherein the distance dependence (of electron transfer) may be very weak [3]. 

Specifically, energy- and charge-transfer properties of several different molecular-wire systems have been studied within the framework of photoinduced charge separation and solar-energy conversion. Up front, the conductance behavior of wire-like molecules was of particular interest. Such features have been carefully examined in view of possible applications in the fields of molecular electronics and/or photovoltaic devices. Among the tested systems, 7t-conjugation played a crucial role. 

In the Center "Probe Microscopy and Nanotechnology" of Moscow Institute of Electronic Technology (Technical University) we started nanotechnology researches in 1985. A number of unique results, including the conductance quantization in quasi-one-dimensional molecular wires at room temperature was demonstrated. Wide area research in a creation of nanoelectronic device principles has been initiated. 

Polyaniline filaments within the mesoporous channel host (aluminosilicate) have significant conductivity, and this demonstration of conjugated polymer with mobile charge carriers in nanometer channels represents a step toward the design of nanometer electronic devices. These composites have potential as stable molecular wires, which can be applied in the design of batteries and systems to accumulate electric charge. SBA-15 with polyaniline inside the pore channels was used as a dispersed phase in electro-rheological (ER) fluids. 

Electrospun nanofibers with electrical and electro-optical activities have received a great deal of interest in recent years because of their potential applications in nanoscale electronic and optoelectronic devices, for example nanowires, LEDs, photocells etc. Besides, one-dimensional (1-D) nanostmctures are the smallest dimensional stmctures for efficient transport of electrons and optical excitations. One of the potential future apphcations of conducting polymer nanofibers is as molecular wires, which are required to connect molecular devices to electrodes. For molecular devices, it is necessary to make nanowires with diameters in the order of the size of the molecular device. 

The construction of intramolecular molecular system whose photo active molecule linked with conducting molecular wire is an important subject in realization of. molecular electronic or photonic devices. For such objectives, systematization of donor-photosensitizer-acceptor triad molecules into large molecular systems is one of the feasible approaches because the exquisite incorporation of the photosensitizer and a suitable electron donor and/or acceptor into a conducting polymeric chain is useful for various molecular systems based on the photoinduced electron transfer. With this in mind, we synthesized symmetrical donor-acceptor-donor triad molecules which can be polymerized by the normal electrochemical oxidation. By the polymerization, one-dimensional donor-acceptor polymers with porphyrin moieties separated by ordered oligothienyl molecular wire which is considered as a proto-type molecular device was obtained. 

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