Anions insertion

Fig. 8. Space Ailing model of a poly-L-lysine a-helix with CIO4 anions inserted between the NH3 -side groups forming a left-handed superhelix 911...

Thus, although this structure cannot be described or understood in terms of any regular anion array or any connected array of cation-centred polyhedra, it is readily and logically visualised as an alloy framework with anions inserted into appropriate (usually tetrahedral) interstices. It must be pointed out, however, that there is a very small distortion of the MusSia structure to give the cation anay in apatite. This consists of a slight rotation of each of the colunms ( rosettes ) at [OOz] - in Fig. 37 clockwise by about 4 . This affects the symmetry, but hardly the geometry. 

Thus, the difference between these structures and the apatites is simply in the choice of tetrahedral interstices in the alloy which are used to accommodate the anions. This determines the type of cation-centred polyhedron for the minority cation. (We ignore the trivial variations in anions inserted into the [OOz] tunnels.) This suggests that the substitution of C03 for P04 in apatites may well be a less radical change than is usually assumed (when anion packing is accepted as being dominant). 

Examples for electrochromic behavior upon electrochemical oxidation can be found among group VIII metal oxides. Thin films of transparent hydrated iridium oxide turn blue-black, whereas nickel oxide switches from pale green to brown-black, possibly due to the absorbance of Ni3+ centers [26]. The systems are much less thoroughly investigated and a detailed mechanistic explanation is not known. However, proton extraction and anion insertion have been suggested. 

This characteristic behaviour is comparable with anionic insertion polymerization rather than with radical polymerization. 

Conducting polymers based on polymer chains with conjugated double bonds are electroactive materials that have found widespread use also in the field of chemical sensors [11-41], Oxidation of the conjugated polymer backbone is accompanied by anion insertion or cation expulsion, as follows ... 

Oxidation pathways involve anion insertion coupled to electron transfer process. In experiments performed on Cu-MOF modified electrodes such as those shown in Figure 5.4, additional anodic peaks located in the 4-0.60 to 4-1.80 V potential region are attributable to the oxidation of polyfunctional organic groups. Such oxidation... 

Redox conductivity of conducting polymers involves anion insertion associated to oxidation processes (p-type doping) and cation insertion coupled with reduction ones (n-type doping). Efficient polymer-based electronic devices require lowering of the redox potential of the involved electron transfer processes, and electrochemical reversibility is necessary to allow repetitive charge/discharge processes. In the... 

As already mentioned, experiments in which allyl compounds were reacted with complex oxides, such as molybdatess or tungstates, or the corresponding anionic insertion of oxygen into the hydrocarbon molecule. The question may thus be raised as to which... 

FeCl4" anions inserted into conjugated polymer matrices exhibit non-zero QS values in all cases studied (Table 4.3). This observation seems to indicate that some distortion of FeCl4 tetrahedra occurs upon the dopant insertion. 

PBD is a very useful tool for identifying the ions that participate in the ion exchange processes that occur during the redox reactions of polymer film electrodes. For instance, the proton expulsion that occurs before anion insertion during the electrooxidation of PANI is clearly seen in the cyclic voltadeflectogram, which is almost... 

The scope of the present chapter is to discuss the properties and preparation of electroactive polymers with emphasis on high conductivity materials. Analogies to inorganic intercalation materials will be used to illustrate the thermodynamic properties of the polymers. Cation insertion may be distinguished from anion insertion by the influence of the solution... 

Figure 2.10 Polypyrrole electropolymerized and cycled in LiC104/acetonitrile exhibits a negative slope which indicates anion insertion.

It has been shown that this process occurs at the three-phase boundary of THPD aqueous electrolyte [solid electrode [135,136]. In situ EPR transients for the oxidation and rereduction of THPD were seen to be consistent with the anion insertion process occurring at the triple phase junction [135]. 

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