Charge transfer reaction from matrix

Charge Transfer Reaction From The Matrix To Polysilanes... 

The radicals C104, S04 , and HP04 described in the previous section represent a few examples of the formation of normally unstable oxidation states of the nonmetallic elements Cl (+8), S( +7) and P( +6) from the corresponding stable, lower oxidation states. In a rigid matrix such as ice, particularly at low temperatures (—e.g., 77 0 K.) these reactive species, once formed, may not be able to take part in chemical reactions. Nevertheless, as seen in the previous section, charge transfer reactions such as those between the solute ions and the primarily formed charged intermediates of ice radiolysis may occur relatively rapidly even under these... 

There is still another type of internal solid state reaction which we will discuss and it is electrochemical in nature. It occurs when an electrical current flows through a mixed conductor in which the point defect disorder changes in such a way that the transference of electronic charge carriers predominates in one part of the crystal, while the transference of ionic charge carriers predominates in another part of it. Obviously, in the transition zone (junction) a (electrochemical) solid state reaction must occur. It leads to an internal decomposition of the matrix crystal if the driving force (electric field) is sufficiently high. The immobile ionic component is internally precipitated, whereas the mobile ionic component is carried away in the form of electrically charged point defects from the internal reaction zone to one of the electrodes. 

In order to extend the analytical usefulness of this type of interaction, we examine the more general reaction between neutral gas molecules and a semiconductor. Because the Fermi level is defined with respect to one electron, the slope of the work function response is expressed in multiples of kT. If a donor molecule, for example, gas G, enters the semiconductor matrix, it transfers (or accepts) a fraction of its electronic charge to (or from) the semiconductor according to... 

Prereactive behaviors were identified very early and an impressive series of examples was listed in a book by Klabunde in 1980 [266]. Electron spin resonance (ESR) studies reveal that in low-temperature matrices electron-transfer reactions are blocked as a rule and most, if not all, charge-transfer complexes involved in standard gas-phase harpoon reactions have been stabilized and observed in matrices. The ESR spectra of these systems revealed nearly complete electron transfer. Similar conclusions have also been drawn from infrared spectroscopy. For example, outside the field of alkali metal atoms, evidence of an AHNO complex has been obtained by this technique [267]. It should not be thought that every metal atom is able to make charge transfer with every molecule. For example, no indication exists of a charge transfer between Cu and NO in an argon matrix [268]. 

Many studies used radiation chemistry to produce the radical and radical cations and anions of various dienes in order to measure their properties. Extensive work was devoted to the radical cation of norbomadiene in order to solve the question whether it is identical with the cation radical of quadricyclane . Desrosiers and Trifunac produced radical cations of 1,4-cyclohexadiene by pulse radiolysis in several solvents and measured by time-resolved fluorescence-detected magnetic resonance the ESR spectra of the cation radical. The cation radical of 1,4-cyclohexadiene was produced by charge transfer from saturated hydrocarbon cations formed by radiolysis of the solvent. In a similar system, the radical cations of 1,3- and 1,4-cyclohexadiene were studied in a zeolite matrix and their isomerization reactions were studied. Dienyl radicals similar to many other kinds of radicals were formed by radiolysis inside an admantane matrix. Korth and coworkers used this method to create cyclooctatrienyl radicals by radiolysis of bicyclo[5.1.0]octa-2,5-diene in admantane-Di6 matrix, or of bromocyclooctatriene in the same matrix. Williams and coworkers irradiated 1,5-hexadiene in CFCI3 matrix to obtain the radical cation which was found to undergo cyclization to the cyclohexene radical cation through the intermediate cyclohexane-1,4-diyl radical cation. 

The u.v. and i.r. spectra of NH3 and Cl2 codeposited in a N2 matrix at 20 K are consistent with the formation of a charge-transfer complex between these molecules.21 The formation of chloramine in high yield from Cl2 and NH3 in the presence of a ketone has been reported.22 Gas-phase as well as gas-liquid-phase reactions were investigated to assess the suitability of this reaction for the production of hydrazine. However, from a study of the acid-base properties of Br2 in liquid NH3 it has been deduced that BrNH2 does not exist in dilute solutions at low temperatures, owing to the stability of the solvated Br+ species.23... 

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