Alkali, chemical coordinates

For isolation of electrode reactants in either an energy storage cell or an electrochemical cell employed for electrosynthesis, a chemically and physically stable, permselective separator membrane is generally required. Two recent classes of polymeric materials are of interest for such application perfluorinated ionomers of which Nafion[48,49] is an example, and alkali metal-coordinating polyethers and polyesters of which polyethylene oxide-LiCFaSOa mixture is an example[50-52]. 

In the skeleton of many chelating diphosphines, the phosphorus atoms bear two aryl substituents, not least because the traditional route to this class of compounds involves the nucleophilic substitution with alkali metal diarylphosphides of enantiopure ditosylates derived from optically active natural precursors, approach which is inapplicable to the preparation of P-alkylated analogs. The correct orientation of these aryl substituents in the coordination sphere has been identified as a stereo chemically important feature contributing to the recognition ability of the metal complex [11,18-20]. 

It could be shown (Fig. 2) that the Li+ ion in DMSO is coordinated by four solvent molecules. y-Butyrolactone was found to be a convenient diluent in this kind of study. Contrary to DMSO (DN — 29.8), it is a rather weak donor (DN = 18.0) which appreciably dissolves alkali metal salts. Its interaction with DMSO is much weaker than that between DMSO and a metal cation. By plotting the chemical shift of the 7Li NMR signal vs. 

In order to characterize the alkali metal salts of the 11-vertex nido-dicarbaborates [C2B9H11]2- in solution, a series of salts were synthesized and studied by NMR spectroscopy and quantum mechanical calculations. Comparison of the theoretical nB, 13C, and H NMR chemical shifts of the isomeric dianions 7,8-, 7,9-, and [2,9-C2B9Hn]Z, and the ion pairs [ap-M-CzBgHn]- and MHP-MC2B9HH] with the observed data indicate that the alkali metal salts M2[C2B9Hn] exist in solution as anionic ion pairs [ap-M-C2B9Hn]- with the metal in apical position (ap) coordinated at the five-membered open face of the cluster.14... 

The use of 2,2,2-cryptand and various crown ethers greatly reduces ion pairing in solution but affects only minor changes in the chemical shifts of the ions. Solvents that reduce K -Sng" ion paring through coordination of the alkali metal ion (e.g., en) also shift the 8 Sn values upheld relative to those solvents that are weakly coordinating (e.g., dmf Table 1). 

Perovskites have the chemical formula ABO, where A is an 8- to 12-coordinated cation such as an alkali or alkaline earth, and B is a small, octahedrally coordinated high valence metal such as Ti, Zr, Nb, or Ta. Glass-ceramics based on perovskite crystals are characterized by their unusual dielectric and electrooptic properties. Examples include highly crystalline niobate glass-ceramics which exhibit nonlinear optical properties (12), as well as titanate and niobate glass-ceramics with very high dielectric constants (11,14). 

Transfer of solute with and relative to the moving water and competitive adsorption of solutes are central to amelioration of saline and alkali soils, agricultural chemical location in soils and management of wastes in soils. This paper illustrates how space-like coordinates based on the distribution of the solid and the water help analyse these problems. We focus on the macroscopic or Darcy scale of discourse [6], which permits unambiguous measurement of the key elements of the flow equations, and we restrict ourselves to 1-dimensional flow, because that seems to limit analysable experiments. 

Protons are relatively simple targets for sensor molecules and do not require engineered receptors, however, achievement of selective interactions with other chemical species requires much more elaborate receptors. In the most cases cations are bound via electrostatic or coordinative interactions within the receptors alkali metal cations, which are rather poor central ions and form only very weak coordination bonds, are usually bound within crown ethers, azacrown macrocycles, cryptands, podands, and related types of receptor moieties with oxygen and nitrogen donor atoms [8], Most of the common cation sensors are based on the photoinduced electron transfer (PET) mechanism, so the receptor moiety must have its redox potential (HOMO energy) adjusted to quench luminescence of the fluorophore (Figure 16.3). 

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