Anion Substitution

If R1 differs from R2. the preparation may lead to both regioisomers. In these cases, a synthetic route which does not rely on allyl anion substitution is often the most advantageous one. Thus, the best results are recorded for allylboronates and -silanes which also possess the required constitutional and configurational stability. 

The intrinsic ion-exchange properties of p-doped polymers have been used to bind electrocatalytic anions such as porphyrins238 and phthalocy-anines.239 Cation-substituted polymers have been used to bind anions such as [Fe(CN)6]3-/4-,235 oxometallates,240 and porphyrins241 and anion-substituted polymers have been used to bind a variety of cationic species such as [Co(2,2/-bipyridine)3]3+/2+)58 [Ru(NH3)6]3+/ 2+,183 and porphyrins.242... 

In principle, the oxidation of proceeds at an electrode potential that is more negative by about 0.7 V than the anodic decomposition paths in the above cases however, because of the adsorption shift, it is readily seen that practically there is no energetic advantage compared to CdX dissolution in competing for photogenerated holes. Similar effects are observed with Se and Te electrolytes. As a consequence of specific adsorption and the fact that the X /X couples involve a two-electron transfer, the overall redox process (adsorption/electron trans-fer/desorption) is also slow, which limits the degree of stabilization that can be attained in such systems. In addition, the type of interaction of the X ions with the electrode surface which produces the shifts in the decomposition potentials also favors anion substitution in the lattice and the concomitant degradation of the photoresponse. 

This strategy has lead to the development of anion-substituted compounds such as Ag3SI and cation-substituted compounds such as RbAg4I5, as well as materials with... 

Peripheral to the Gal-GlcNAc sequences of glycoproteins, there can occur an array of blood-group-related glycosylations, anionic substitutions (sialy-lation, 0-sulfation, and 0-phosphorylation), or both. Chains of the high-mannose type may also bear phosphate groups. Table VI reviews the pat-... 

While the greatest percentage of PTC-aided anionic substitutions involve non-aromatic systems (7-10), a number of liquid-liquid and solid-liquid, PTC-aided SnAr reactions have been reported (32-38). These reports involve a variety of substrates [unactivated (32,33), slightly activated (M), activated (35-37), and transition metal complexed 32,38)1, nucleophiles OMe (32,38), CN ( ), SR (34) SCN (36), SO (36), OR (37)] and PTCs... 

T o express mineral chemical formulas the cations or anions substituting in a unique site in the structure are combined. 

Anionic substitution of F for O in Nd2Cu04 also results in bulk superconductivity with Tc s as high as 27K (89). To obtain superconductivity in these crystals, a complicated post-annealing procedure is required. So far, the fraction of the crystal which becomes superconducting appears to be relatively small (90). 

In conclusion it may be said that work is still in progress with regard to understanding anion substitution in AFm and AFt phases. 

Examples of Dimensional Reduction via Core Anion Substitution... 

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