Chemical switching

Chemical Switching and Gating of Current Through Nanoclusters... 

Willey, T.M., Vance, A.L., Bostedt, C., van Buuren, T., Meulenberg, R.W., Terminello, L.J., and Fadley, C.S. (2004) Surface structure and chemical switching of thioctic acid adsorbed on Au(lll) as observed using absorption fine structure. Langmuir 20(12), 4939-4944. 

Alfassi, Z. B., and Benson, S. W., A simple empirical method for the estimation of activation energies in radical molecule metathesis reactions, Int. J. Chem. Kinetics S, 879 (1973). Allara, D. L., and Edelson, D., A computational analysis of a chemical switch mechanism. Catalysis-inhibition effects in a copper surface-catalyzed oxidation, J. Phys. Chem. 81, 2443 (1977). 

Another redox switchable system is based on dyad 21 in which 2-chloro-1,4-naphthoquinone is covalently attached to 5-dimethyl-aminonaphthalene via a non-conjugated spacer. The intrinsic fluorescence of the dansyl excited state in dyad 21 is strongly quenched, due to the intramolecular electron transfer from the excited dansyl to the adjacent quinone acceptor. However, the fluorescence can be switched on by addition of a reducing agent. Apart from chemical switching, the fluorescence of dyad 21 can also be switched electrochemically. This can be realized using a photoelec -trochemical cell, and the solution starts to fluoresce upon application of a reductive potential.31... 

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... 

Fig. 8.7 Chemical switching of an amphiphilic bistable [2]rotaxane 64+ in a condensed phase, monitored by X-ray photoelectron spectroscopy.

Bishop AC, Ubersax JA, Petsch DT et al (2000) A chemical switch for inhibitor-sensitive alleles of any protein kinase. Nature 407 395 -01... 

In addition, the absorption spectra and fluorescence intensity of some porphyrins changed along with the photochromic reaction of the dithienylethene functional group, which was possible for constructing some optical chemical switching systems with emission signal. 

T. Hofmann, Acetylformoin — a chemical switch in the formation of colored Maillard reaction products from hexoses and primary and secondary amino acids, J. Agric. Food Chem., 1998, 46, 3918-3928. 

We have developed a number of these supramolecular machine-like systems in collaboration with the Balzani group, and have used them to perform logic functions. An example is presented in the next section. Figure 28 illustrates the chemical switching [20a] of the [2]pseudorotaxane [8=>39]2+, which incorporates a re-electron-deficient unit (dia-zapyrenium dication) in its thread-like component 392+ and two re-electron-rich units (DNP) in the crown ether 1/5-DN38C10 (8). Since the thread-like component 392+ forms adducts... 

Bencic-Nagale S, Stemfeld T, Walt DR. Microbead chemical switches an approach to detection of reactive organophosphate chemical warfare agent vapors. J Am Chem Soc 2006 128 5041-8. 

Scrase-Field, S.A.M.G. and Knight M.R., 2003, Calcium just a chemical switch Curr. Op. Plant Biol. 6 500-506. 

If the chemical is absorbed and bypasses our defenses, the chemical must then get into a cell or activate a receptor (a chemical switch) to have an effect. The binding to a receptor, which requires some specific chemical attribute, can then alter the cell s function or even activate a so-called oncogene that can result in cancer. Binding to a receptor itself is a dose-response phenomenon, and there is a threshold below which no effect is caused. 

Anthony C. Bishop, Jeffrey A. Ubersax, Dejah T. Petsch, Dina P. Matheos, Nathanael S. Gray, Justin Blethrow, Elji Shimizu, Joe Z. Tsien, Peter G. Schultz, Maik D. Rose, John L. Wood, David O. Moigan and Kevan M. Shokat, A chemical switch for inhibitor-sensitive alleles of any protein kinase. Nature, 407 (2000), 395-401. 

Sasaki T, Ikeda T. 1995b. Photochemical control of properties of ferroelectric liquid crystals. 2. Effect of the structure of guest photoresponsive molecules on the photo chemical switching of polarization. J Phys Chem 99 13008 13012. 

For example, the rotary motion of ATP synthase was commandeered by Montemagno and coworkers to drive a nanoscale metal propeller at a rate of around five revolutions per second.Protein engineering was used to insert a zinc-operated chemical switch into the enzyme to turn it on and off (Fig. 6). 

Fig. 6 (a) Electrochemical and chemical switching in a molecular shuttle. Reprinted with permission from Ref. [17]. Copyright 1998... 

The [Ir(ppy)2bpy] complex photo-catalyses inter- and intramolecular C-H functionalisation reactions of tertiary amines under the visible light irradiation. Oxygen behaves as a chemical switch, triggering different reaction pathways and leading to different products from the same starting material. In anaerobic conditions, the intermolecular addition of iV,iV-dimethyl-anilines to electron-deficient alkenes yields y-amino nitriles. Aerobic conditions, on the other hand, favour a radical addition/ cyclisation reaction, leading to tetrahydroquinoline derivatives. The intramolecular version of the radical addition produces unexpectedly indole-3-carboxaldehyde derivatives. ... 

Because of the redox responsiveness of the TTF hook guest, oxidation of these precipitates demonstrated the reversible nature of network formation as the amorphous precipitates could be dismpted and were observed to redissolve in solution. Reduction led again to the formation of NP precipitate and the chemical switching was demonstrated for several cycles. In addition, this property was further exploited as TTF is known to form much more stable pseudorotaxane complexes with blue box than with Np. A mixture of both TTF-AgNPs and Np-AuNPs with the blue box polymer 64 leads primarily to a silver-rich precipitate of AgNP aggregates as characterized by electron miaographs and electron dispersive analysis of the... 

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