Influence of cations

C. Influence of Cationization of the Azine Moiety and of Hydrogen Bonding to the Azine-Nitrogen... 

Arndt and Ahlers [38] used X-ray powder diffraction method for studying the influence of cations on the mode of action of miconazole on yeast cells. The influence of miconazole nitrate on yeast plasma membranes was studied in a concentration range of 0-100 pM. The reaction of 100 pM miconazole with the... 

The sizes of the voids decrease in order Cs, Rb, Na, K These differences are ascribed to the different influence of cation on the surrounding reactive species that changes the nature of alkali cation - aluminosilicate anion complexes. On the other hand, in the case that the cations are introduced in the matrix by ion exchange, (procedure b) the r3 lifetimes are approximately the same for all the cations (Table 2) and the size of cation does not have such pronounced influence. The calculated radii are shown in Table 4. 

The fourth lifetime components, r4, have values in the range of 2.7 - 5.0 ns (shown in Table 1 and 2), which, using equation (1), gives 0.34 - 0.47 nm for radii of the holes that are listed in Table 3 and 4. These lifetimes have also lower intensities than r3, suggesting the presence of the larger voids already in the initial phase of zeolite formation, but in a smaller extent. Here the correlation to the influence of cation sizes cannot be established. 

For some reviews, see (a) Majoral J-P (2007) Influence of cationic phosphorus dendrimers on the surfactant-induced synthesis of mesostructured nanoporous silica. New J Chem 31 1259-1263 (b) Puntoriero F, Nastasi F, Cavazzini M et al (2007) Coupling synthetic antenna and electron donor species a tetranuclear mixed-metal Os(II)-Ru(II) dendrimer containing six phenothiazine donor subunits at the periphery. Coord Chem Rev... 

Wolfert MA, Dash PR, Nazarova O, et al. Polyelectrolyte vectors for gene delivery influence of cationic polymer on biophysical properties of complexes formed with DNA. Bioconjug Chem 1999 10(6) 993-1004. 

Studying the transition from (semi)metallic to ionic stmctures. It became evident that the use of different or different combinations of electropositive metals led to variations in size and shape of the polyanionic moiety. For some elements this was extensively studied, and a direct influence of cation-element interaction on size, structure, and functionahty of the polyanions was emphasized. These interactions are naturally strong for small cations and become less strong the higher the period, in accord with the corresponding radii. 

Figure 1.1 The influence of cation and anion on the density of imidazolium [C Cilm][X] ionic liquids at T = 298.15 K, where n = 1-10 and anions [X] are [Tf2N] (black), [AlCy" (light grey), [BF4] (dark grey), and [PFs]" (white).

Figure 1.11 The influence of cation on the solid-liquid phase equilibria diagram (IL + water [(Cj )2(Cj)2N][N03j (O) and [Be(Cj)2CJ[N03] ( ). (Adapted from Domahska, U., B kala, L, and Pernak, J. Chem. Eng. Data, 52, 309, 2007 Domahska, U., Lugowska, K., and Pernak, J., /. Chem. Thermodyn., 39, 729,2007.)...

A detailed study of the influence of cations (299) on the Rf or P values of the separate phosphate components showed that the substances which... 

An anionic gel that contracts under the influence of cations... 

III. Influence of Cation Properties on Metal(I) Coordination Number... 

Rationalization of the detailed geometry of the particular halogeno-cuprate(I) or halogenoargentate(I) ion in terms of the influence of cation shape or positive charge distribution is, however, much more complex. Whereas it has proved possible to employ cations predictively for anion design in series of compounds containing comparable cations, e.g., symmetrically substituted tetraalkylammonium and phosphonium analogs (cf. 60, 71, 72), it seems doubtful that cations of disparate shape can be used as other than predictors of metal(I) coordination number. 

It should be kept dearly in mind that the radius ratio rules apply strictly only to the packing of hard spheres of known size. As this is seldom the case, it is surprising that the rules work as well as they do. Anions are not hard like billiard balls, but polarizable under the influence of cations. To whatever extent such polarization or covalency occurs, errors are apt to result from application or the radius ratio rules. Covalent honds are directed in space unlike electrostatic attractions, and so certain orientations are preferred. 

Influence of Cations on the Thermal Stability of Modified Y Zeolites... 

Zeolite A. The structure of zeolite A contains two types of voids (1) the a cage, 11.4 A in diameter, and (2) the P cage (or sodalite unit), 6.6 A in diameter (7). Table I compares experimentally determined pore volumes of zeolite A with the void volume as calculated from the structure (no influence of cations considered). Since the sodium zeolite A does not adsorb normal paraffins, data are included for the calcium-exchanged form. Also shown in column 5 is the void fraction, Vi, as calculated by... 

For Xe in Ba-, Na-, and K-forms of zeolite L heats are in the order Ba > Na > K so that an influence of cation appears which is in the sequence of the polarizing power. A rather small polarization energy contribution to q8t is then sufficient to account for most of the differences. All heats decline monotonically with amount sorbed but often in rather specific ways. 

Chiarizia, R., Jensen, M.P., Rickert, P.G. et al. 2004. Extraction of zirconium nitrate by TBP in n-octanc Influence of cation type on third phase formation according to the sticky spheres model. Langmuir 20 (25) 10798-10808. 

Figure 11. Influence of cationic surfactants on the stability of polystyrene latices in comparison with potassium bromide (A)- Alkyl trimethyl ammonium bromides of various chain lengths (A) Ch (U) C8 O Ciol (+) Cn (O) C16.

The ionic radius criterion for interpreting geochemical distributions of trace elements was given a boost in the early 1970 s when correlations were shown to exist between ionic radii and partition coefficients of some trace elements (Onuma et al., 1968 Higuchi and Nagasawa, 1969 Jensen, 1973). The influence of cation radius and charge on trace element distribution patterns was demonstrated by measurements of the distribution coefficient, >, defined by... 

Figure 9.9. Influence of cation concentration and valence on zeta potential (from Taylor and Ashroft, 1972, with permission).

Such a local approach is now widely used and works quite well. It provides a natural explanation of the trend toward increasing zeolite stability with Si/Al ratio. It also allows one to follow easily the influence of cations entering a zeolite structure on its stability. Quite a number of such comparative calculations can be found in the literature. We shall confine ourselves to only a few representative examples. 

KOlkenbeck K, Zundel G (1975) The significance of the 2 -OH group and the influence of cations on the secondary structure of the RNA backbone. Biophys Struct Mechanism 1 203 -219... 

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