Indium redox reactions

Very recently a new kind of electrocatalyst has been propounded using the dinuclear quinone-containing complex of ruthenium (25).492,493 Controlled-potential electrolysis of the complex at 1.70 V vs. Ag AgCl in H20 + CF3CH2OH evolves dioxygen with a current efficiency of 91% (21 turnovers). The turnover number of 02 evolution increases up to 33,500 when the electrolysis is carried out in water (pH 4.0) with an indium-tin oxide(ITO) electrode to which the complex is bound. It has been suggested that the four-electron oxidation of water is achieved by redox reactions of not only the two Run/Ruin couples, but also the two semiquinone/quinone couples of the molecule. 

The mixed-valent gold indium cluster [Au3ln3Cl6(dppe)2] is composed of In(I) and In(II) atoms. Synthetic details were presented in an earlier section. Insertion and redox reactions of In(I) halides have been described. For example, oxidative addition reactions of InX (X = Cl, Br, I) with PhSSPh yields indium(III) thiolates of the type (PhS)2lnX." Unexpected In(II) or In(III) products are common in reactions involving indium(I) halides, which result from facile disproportionation processes. Several such cases were described with divalent indium compounds. 

A chemical detector for ascorbic acid is a polybithiophene-modified indium tin oxide (ITO) glass electrode. Reduction of the polymeric layer occurs when doped polymeric films are brought into contact with an aqueous solution of ascorbic acid. This redox reaction is clearly indicated by the change in the chromatographic property of the film [213]. 

Interest in the preparation of galHum-containing and indium-containing zeolites by reductive solid-state ion exchange was stimulated by the fact that these materials might also be promising catalysts for aromatization of alkanes and redox reactions, respectively. 

In view of the above redox cycles. In-containing zeoUte catalysts prepared by RSSIE are obviously promising candidates for redox reactions, because of their fully reversible changes in the oxidation state of the indium species incorporated and stabiUzed in the zeolite matrices. 

The rather complicated indium-phosphorus cluster framework 24 was obtained by the reaction of indium(III) chloride with PhP(SiMe3)2 in the presence of triethyl-phosphane [Eq. (12)] [29]. Apparently, a complex redox process occurred, in the course of which phosphorus atoms were oxidized by the formation of three P-P bonds, while six indium atoms were reduced from +3 to +2 accompanied by the formation of three In-In bonds. The In-In (average 274 pm) and P-P bond lengths (average 222 pm) represent localized single bonds. Other strategies for the... 

Modified TiC>2 surfaces have also found application in the design of fast elec-trochromic devices. The influence of the substrate on the behavior of interfacial assemblies is well illustrated in this book. However, it is important to realize that the electrochromic behavior observed for modified TiC>2 surfaces was not expected. The oxidation and reduction of attached electrochromic dyes are not mediated by the semiconductor itself but by an electron-hopping process, not unlike that observed for redox polymers, where the electrochemical reaction is controlled by the underlying indium-tin oxide (ITO) contact. These developments show that devices based on interfacial assemblies are a realistic target and that further work in this area is worthwhile. 

Solutions of indium (I) can be prepared by treatment of indium amalgam with silver triflate in dry acetonitrile in the absence of oxygen, and then diluted with water to give the low-concentration aqueous solution, which plays a sizable role in the study of the details of intermolecular electron transfer processes in solution. Aqueous In(I) solution has been used to examine the behavior of this hypovalent center in inorganic redox transformations. Reactions with complexes of the type [(NH3)5Co (Lig)] and [(NH3)5Ru (Lig)] (Tig = Cl, Br , I or HC2O4 ) show two consecutive one-electron reactions initiated by the formation of the metastable state In , which is then rapidly oxidized to In , and the first of which is predominating an inner-sphere mechanism. ... 

The first reports on a reversible DET between redox proteins and electrodes were published in 1977 showing that cytochrome c is reversibly oxidized and reduced at tin-doped indium oxide [30] and gold in the presence of 4,4 -bipyridyl [31]. Only shortly after these publications appeared, papers were published describing the DET between electrode and enzyme for laccase and peroxidase [32,33]. It was observed that the overpotential for oxygen reduction at a carbon electrode was reduced by several hundred millivolts compared to the uncatalyzed reduction when laccase was adsorbed. This reaction could be inhibited by azide. The term bioelectrocatalysis was introduced for such an acceleration of the electrode process by... 

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