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Probe acceptor/anion

Raman spectroscopy has up to now mainly been applied to elucidate conformational forms and associated conformational equilibria of the IL components. Yet other applications are appearing in these years. One example is the characterization of metal ions like Mn, Ni Y Cu Y and Zn + in coordinating solvent mixtures by means of titration Raman Spectroscopy [118]. Another issue is the study of solvation of probe molecules in ILs. In such a study [118], for example, acceptor numbers (AN) of ILs in diphenylcyclopro-penone (DPCP) were estimated by an empirical equation associated with a C=C / C=0 stretching mode Raman band of DPCP. According to the dependence of AN on cation and anion species, the Lewis acidity of ILs was considered to come mainly from the cation charge [119]. [Pg.346]

Limitations in using anionic probes such as ANS and CPA to determine protein hydrophobicity include the possibility that electrostatic as well as hydrophobic interactions may contribute to the interaction between the protein and the probe (Greene, 1984). The use of charged but neutral probes (having both electron donor and acceptor groups e.g., prodan) or uncharged probes (e.g., DPH Davenport,... [Pg.309]

It is now well established that a variety of organic molecules such as polynuclear aromatic hydrocarbons with low ionization energies act as electron donors with the formation of radical cations when adsorbed on oxide surfaces. Conversely, electron-acceptor molecules with high electron affinity interact with donor sites on oxide surfaces and are converted to anion radicals. These surface species can either be detected by their electronic spectra (90-93, 308-310) or by ESR. The ESR results have recently been reviewed by Flockhart (311). Radical cation-producing substances have only scarcely been applied as poisons in catalytic reactions. Conclusions on the nature of catalytically active sites have preferentially been drawn by qualitative comparison of the surface spin concentration and the catalytic activity as a function of, for example, the pretreatment temperature of the catalyst. Only phenothiazine has been used as a specific poison for the butene-1 isomerization on alumina [Ghorbel et al. (312)). Tetra-cyaonoethylene, on the contrary, has found wide application as a poison during catalytic reactions for the detection of active sites with basic or electron-donor character. This is probably due to the lack of other suitable acidic probe or poison molecules. [Pg.245]

Photochemical electron transfer reactions have been examined in micellar systems as probes for the diffusion and location of quenchers, and as environments for solar energy storage 2 3>90 95 96>. The relative rates of quenching will depend on the location of the donor and acceptor (Scheme XXXII). For example, the rate of quenching of a hydrophobic donor located inside the micelle by Cu2+ is much faster in anionic micelles compared to cationic micelles. Similarly a hydrophobic excited state is quenched faster by a hydrophobic donor or acceptor than by a hydrophilic one in micellar systems. [Pg.94]

HS-GC has been developed to serve as a sensitive tool to determine even small differences in the solvation properties of ionic liquids using a choice of model solutes featuring specific interactions molecular ion-dipol interactions, hydrogen bond donor and acceptor interactions, and n- and n-electron dispersion forces can be probed by model solutes such as acetonitrile, 1,4-dioxane, n-propanol, n-heptane and toluene, respectively. Bearing in mind that no solute exhibits exclusively one specific interaction, the systematic investigation of the effect of the variation of the structural elements of ionic liquids, i.e. choice of cation, cation substitution and anion, lead to the following conclusions. [Pg.59]

Catalysts active in the isomerization of n-butane have been synthesized by depositing sulfate ions on well-crystallized defective cubic structures based on ZrOz. This technique for introduction of sulfates does not result in any significant changes in the bulk properties of zirconium dioxide matrix. Active sulfated catalysts were prepared on the basis of cubic solid solutions of ZrOz with calcium oxide and on the basis of cubic anion-doped ZrOz. The dependence of the catalytic activity on the amount of calcium appeared to have a maximum corresponding to 10 mol.% Ca. Radical cations formed after adsorption of chlorobenzene on activated catalysts have been used as spin probes for detection of strong acceptor sites on the surface of the catalysts and estimation of their concentration. A good correlation has been observed between the presence of such sites on a catalyst surface and its activity in isomerization of n-butane. [Pg.353]

Electron transfer reactions have also been used in the probing of solute-solute interactions in supercritical fluid solutions. For example, Takahashi and Jonah examined the electron transfer between biphenyl anion and pyrene in supercritical ethane (192). Worrall and Wilkinson studied triplet-triplet energy transfer reactions for a series of donor-acceptor pairs, including anthracene-azulene in supercritical C02-acetonitrile and supercritical C02-hexane and ben-zophenone-naphthalene in supercritical C02-acetonitrile (193). The high efficiency of the energy transfer reactions at low cosolvent concentrations was attributed to the effect of solute-solute clustering. [Pg.53]


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