Molecular rectifier

On a molecular level, exactly the same characteristics are required of supramolecular components and hence a molecular rectifier should comprise an electron donor and an electron acceptor, separated by an insulating spacer. Compounds 11.49 and 11.50 are based on cr-insulating framework, while donor-acceptor carotenoid derivatives such as 11.51 are separated by a more conducting r-system. 

An old and stiU important goal of molecular electronics is the production of a molecular rectifier. This concept refers to molecules or functional units which can be arranged mutually parallel in a molecular architecture and are structured in such a way that an electric current flows through them asymmetrically their electrical conductivity is thus considerably higher in one direction than in the opposite direction. 

The molecules were laid onto an Al electrode as an LB film in one or in several layers. The counterelectrode, likewise Al, was evaporated in vacuum (Fig. 12.11). Using this arrangement, current-voltage curves were measured and are shown in Fig. 12.12. They do in fact exhibit a rectifier characteristic. From the measured data, an electron transfer rate of et = 0.5 electrons per molecule and second was calculated. 

demonstrates the possibility of fabricating a unimolecular rectifier. More details can be found in the summary article [18]. Technical applications 

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One of the advances in the field of PET is the design of molecular devices, in which D and A pairs are ingeniously linked by covalent bridges (B) to form D-B-A dyads. Electron transfers between D and A across B in a controlled manner may thus display useful functionalities, such as molecular rectifiers [25], switches [26], biosensors [27], photovoltaic cells [28], and nonlinear optical materials [29]. Spacers that have been utilized are versatile, including small molecules, such as cyclohexane [30], adamantane [31], bicyclo[2.2.2]octane [32], steroids [33], and oligomers of... 

Aviram A, Ratner MA (1974) Molecular rectifiers. Chem Phys Lett 29(2) 277-283... 

UE began with Aviram and Ratner s 1973 proposal for a molecular rectifier this is the third rectification process [79]. An Aviram-Ratner rectifier has donor and acceptor groups in one molecule, separated by an insulating bridge of sigma... 

Martin AS, Sambles JR, Ashwell GJ (1993) Molecular rectifier. Phys Rev Lett 70 218-221... 

Ho G, Heath JR, Kontratenko M, Perepichka DF, Arseneault K, Pezolet M, Bryce MR (2005) The first studies of a tetrathiafulvalene-o-acceptor molecular rectifier. Chem Eur J 11 2914-2922... 

Molecular Rectifiers and Negative Differential Resistance Devices. 234... 

Fig. 15 A molecular OR gate, whose chemical structure maps the electrical circuit diagram shown in Fig. 20a. Two Aviram-Ratner molecular rectifier chemical groups have been bonded to a central chemical node. This intramolecular circuit with one simple node can be easily designed, because the node Kirchoff node law is valid here. Note that the molecular orbital of each partner can be still identified on the 2 T(E) because of their weak interactions through the CH2 bridge. This is not always the case. The obtained logic surface demonstrates an OR function for well-selected values of the input voltage, but with two logical level 1 outputs which would have to be corrected using an additional output circuit...

Jlidat N, Hliwa M, Joachim C (2009) A molecule OR logic gate with no molecular rectifier. Chem Phys Lett 470 275... 

Fig. 10 (a) Schematic representation of the I-V measurement of the Cgo derivative based molecular rectifier, (b) I-V characteristics of the Langmuir-Blodgett film of the fullerene penta-pod showing current rectification at bias voltage of 1.0 V measured at different junction positions, with high rectification ratios (RR) registered at each junction. (Reprinted with permission from [98])... 

Fig. 11 (a) Molecular orbital location in a C o based molecular rectifier, (b) Typical current-voltage characteristics recorded for HgATFPP/Cgo/SiCn ) structure (schematic shown in the upper inset). The lower inset shows a symmetric I-V curve recorded for the Hg/C6o/Si(n ) structure. (Reprinted with permission from [99])... 

Aviram A, Ratner MA (1974) Molecular rectifiers. Chem Phys Lett 29 277-283 Viani L, dos Santos MC (2006) Comparative study of lower fullerenes doped with boron and nitrogen. Solid State Commun 138 498-501... 

Gayathri SS, Patnaik A (2006) Electrical rectification from a fullerene[60]-dyad based metal-organic-metal junction. Chem Commun (Cambridge, UK) 1977-1979 Matino F, Arima V, Piacenza M et al (2009) Rectification in supramolecular zinc porphyrin/ fulleropyrrolidine dyads self-organized on gold(lll). Chemphyschem 10 2633-2641 Acharya S, Song H, Lee J et al (2009) An amphiphilic Cgo penta-addition derivative as a new U-type molecular rectifier. Org Electron 10 85-94... 

There have been some impressive, relatively recent examples of molecular rectification. Compound 11.52 has proved to be an extremely efficient molecular rectifier, able to actually function as a rectification device by intramolecular tunnelling either as a monolayers or multilayer macroscopic film or on a nanoscopic level.51 Switchable rectification has been demonstrated for a related dye shown in Figure 11.36. The electrical asymmetry can be chemically switched, off and then back on, by treatment with acid and base, respectively. Protonation disrupts the intramolecular charge-transfer axis, destroying the rectification effect.52 Recent calculations, however, suggest that there may be relatively unpromising theoretical limits on the rectification possible by a single molecule.53... 

Armstrong, N., Hoft, R. C., McDonagh, A., Cortie, M. B., Ford, M. J., Exploring the performance of molecular rectifiers Limitations and factors affecting molecular rectification. Nano Letters 2007, 7, 3018-3022. 

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