Molecular scale electronics

We have surveyed tire remarkable progress in tire field of ET reactions, and have examined some of tire key applications and successes of tire tlieory. Many of tire current frontiers of ET research he in biological systems and in molecular-scale electronic devices. 

The possibility of coordinating functionalized TTFs onto polynuclear core is a very stimulating issue because it is now well established that polynuclear cores, with some restrictions of course, can act as SMMs. We started a systematic investigation of polynuclear paramagnetic complexes with TTF CH=CH—py ligands to scan the possibility to access to bifunctional molecules which can act at the same time as SMM and single component metal. We succeeded in coordinating our modified TTFs to several homo- or heteropolynuclear complexes. This opens new perspectives in the field of multifunctional materials. The size of these molecules, which is of the order of 4 nm, is another important aspect in the field of molecular scale electronic. 

Reinerth WA, Jones LII, Burgin TP, Zhou C-w, Muller CJ, Deshpande MR, Reed MA, Tour JM (1998) Molecular scale electronics syntheses and testing. Nanotechnology 9(3) 246... 

Tour JM, Kozaki M, Seminario JM (1998) Molecular-scale electronics a synthetic/compu-tational approach to digital computing. J Am Chem Soc 120 8486-8493... 

The interest in TTF and TCNQ begat a seminal theoretical proposal on one-molecule rectification (Aviram and Ratner, 1974) which started unimolecular, or molecular-scale electronics. 

However, few or none of those 1012 electrons per second were colliding with the nuclei of the molecule, therefore all the heat was dissipated in the contact. Note that the mean tree path of an electron in a metal is hundreds of angstroms. Hence, it is not surprising that collisions, within a small molecule, did not take place Most importantly, since most computing instruments operate on microamps of current, the prospects for molecular scale electronics are quite intriguing. 

J. M. Tour, M. Kozaki, J. M. Seminario, Molecular Scale Electronics A Synthetic/Computational Approach to Digital Computing, J. Am. Chem Soc 1998, 120, 8486-8493. 

A. Rawlett, J. Chen, M. A Reed, J. M. Tom, Advances in Molecular Scale Electronics Synthesis and Testing of Molecular Scale Resonant Tunneling Diodes and Molecular Scale Controllers, Polym. Mater, Sci. Engin (Am Chem Soc, Div. Polym Mater) 1999, 81,140-141. 

R. Wu, J. S. Schumm D. L Pearson, J. M. Tour, Convergent Synthetic Routes to Orthogonally Fused Conjugated Oligomers Directed Toward Molecular Scale Electronic Device Applications, I. Org. Chem. 1996, 61, 6906-6921. 

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. 

Thus, the ideas behind the bottom-up approach are as simple as powerful. The general aim lies in the design of novel materials employable for molecular-scale electronics, such as molecular transistors, molecular photovoltaic applications, molecular display technology, etc. Hereby, the functions are carefully adjusted by synthetic tools to build up a certain chemical structure. In this context, we need to address the key steps/challenges in such a work-flow. With this in hands the impetus of this thesis should be illustrated. 

The progress in developing controlled attachment chemistries has opened up a range of opportunities for designing and fabricating molecular scale electronic devices based on these monolayers. Electrical transport through alkyl monolayers on silicon has been relatively well studied, particularly using electrochemical methods and Hg drops. The work of... 

As in the past two years, fullerenes continue to be a source of considerable photochemical interest and photoinduced electron transfer is a central theme of numerous studies. The field of molecular-scale electronic devices continues to promote interest in the photophysical properties of novel molecular architectures and such aspects of photoactive rotaxanes and catenates have been reviewed (Benniston and Chambron et ai), while Harriman and Ziessel have outlined the design principles associated with the construction of photo-activated molecular wires. 

Related molecular dyads have been constructed in which a metal complex, often ruthenium(II) tris(2,2 -bipyridine) or similar, functions as chromophore and an appended organic moiety acts as redox partner. Other systems " have been built from two separate metal complexes. Each of these systems shows selective intramolecular electron transfer under illumination. Rates of charge separation and recombination have been measured in each case and, on the basis of transient spectroscopic studies, the reaction mechanism has been elucidated. The results are of extreme importance for furthering our understanding of electron-transfer reactions and for developing effective molecular-scale electronic devices. The field is open and still highly active. 

Photoswitchable materials could be important components in molecular-scale electronic devices and several new systems have been reported. There have been other investigations of phototropic systems in which light is used to drive a reversible conformational change " or, in the case of liquid crystals, a phase transformation. Such photosystems are of interest for the engineering of microscopic photoactive devices but the subject is still in its infancy and practical devices remain elusive. Much more subtle is the use of light to trigger a change in... 

Another line of STM manipulation research that has attracted similar interest is the construction of quantum electronic structures (atomic and molecular-scale features that constrain electron movement in one, two, or three dimensions). Recent reports offer some preliminary indication that such structures may also eventually be employed to construct molecular-scale electronic devices. 

Since the pioneering contributions of Scrocco, Tomasi, and their collaborators [14,15], the evolution of which has been described in an excellent fashion by Tomasi et al. [23], the use and applications of molecular electrostatic potentials have dramatically expanded. (For recent overviews, see Refs. 3 and 24.) This is continuing, with F(r) now involved in the development of molecular-scale electronic systems [25]. 

To summarize, the EFM technique is a useful tool to study the electronic properties of isolated conducting materials and various semiconductor films on dielectric snbstrates at an early stage of growth. Using charge injection from the AFM tip, it is also nsefnl to characterize molecules of interest for molecular-scale electronics [112]. 

Gust D, Moore TA and Moore AL (1997a) Photosynthesis as a paradigm for molecular-scale electronics. Molecular Nanotechnology—Biological Approaches and Novel Applications, IBC, Southborough, MA, Ch. 2.1, 2.1.1-2.1.39... 

Lee, C., Kang, Y., Lee, K. et al. 2002. Molecular wires and gold nanoparticles as molewares for the molecular scale electronics. Current Applied Physics 2 39-45. 

Molecular electronics" (ME) (sensii stricto), or molecular-scale electronics" or unimolecular electronics" (UE) is the study of electrical and electronic processes measured or controlled om a molecular scale or on the nanometer scaleJ A wider definition of molecular electronics sensu lato), or "molecule-based electronics" encompasses electronic p ocesses by molecular assemblies of any scale, including macroscopic crystals and conducting polymers/ This article deals with UE and focuses on electrical conduction (asymmetric or not), through single molecules or through a monolayer of molecules measured in parallel. 

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