Anionic interactions binary structures

Chrenkova et al. (1998) studied the structure or ionic composition of the melts of the system KF-KCl-KBF4-K2TiF6 based on the measurements of phase equilibria, density and viscosity and using complex thermodynamic and physico-chemical analysis. From the results of the physico-chemical analysis, it follows that deviations from the ideal behavior were observed in all boundary binary, ternary, as well as in the quaternary systems. With regard to the fact that the investigated system has a common cation, the observed deviations from the ideal behavior have to be a consequence of the anionic interaction only. 

The important point to appreciate is that the formal valency of zinc is satisfied by two bonds to sulfur so that the additional interactions are indeed hypervalent interactions. Thus, the nature of the adopted structures arises from the ability of the central element to form hypervalent, or secondary, interactions and it is proposed that this ability is moderated by steric considerations associated with the alkyl substituents. As noted from the structural studies for the uncoordinated xanthate anions summarized earlier in Section II, there are no electronic differences among the xanthate ligands that can be correlated with the nature of the oxygen-bound substituent. This conclusion is vindicated by the homogeneity of the molecular structures of the binary nickel xanthates as... 

The interaction of the column anions suggests that binary and ternary calcium apatite phosphates are not mere additions of the end-member structures, but that structural adjustments must occur to accommodate mixed-anion columns. Table 2 depicts the distance between anion occupants of adjacent planes, and illustrates which adjacent neighbors are allowed with mixtures of the end-member structures. 

Compared to systems based on a single interaction, cooperative sensors based on multiple, concerted, inter-molecular interactions between the components exhibit higher discrimination capabilities and enhanced functions. As examples for this class of sensors, two systems, both based on the absorption/luminescence properties of the porphyrin nucleus are illustrated in Fig. 5. Structure (a) represents a ditopic receptor where cooperative binding of a cation by the amide-appended calixarene and of an anion by the Zn-porphyrin allows recognition of complete binary metal salts. Structure (b) incorporates two cyclodextrin cavities and relies on the modification of the Fe(III) complex spectroscopic properties by inclusion of guests in these hydrophobic sites.This species is able to sense the presence of benzylmercaptane and 1-adamantanecarboxylate in four... 

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