Interactions between cations and anions

This corresponds to a decreased energy of the interaction between cation and anion caused by an increased level of anion complexation. When one takes the atomic charges of the cationic centre (carbon atom) into consideration, the improvement of the anion properties becomes clearer (see Fig. 9). 

In this article, we have focused on the arrangements of one component, neglecting interactions between cations and anions, and examined how close they are to close packing. However, the analyses have suggested that close packing" is not the principle that determines the structure. In compounds, close packing is a simple motif that appears as a consequence of complex local interactions. 

When the absolute value of xmjCa increases, standard deviation also increases. This is consistent with the physical meaning of xm ca. The larger the absolute value of Tm>ca, the stronger the interaction between cation and anion. In... 

One of us has used molecular polarization potentials (MPP) to study the interaction of aromatic molecules, including furan, thiophene, and pyridine with a positive unitary charge, these maps being powerful tools for the study of intermolecular interactions and chemical reactivity [129,130], This kind of study leads us to examine theoretically the problem of the interaction between cations and anions with aromatic rings. We were pioneers in proposing that, in parallel with cation-7i-systems (for instance, benzene), there should exists anion-perfhiorinated-7i-systems (for instance, hexafluorobenzene) [131]. These studies include tetrafluorofuran and tetrafluorothiophene (128, 129). Simultaneously, Mascal et al. [132] described the same phenomenon but with 1,3,5-triazine (130) and 2,4,6-trifluoro-l,3,5-triazine (131) as acid 7i-systems. The group of the University of Palma de Mallorca has published a large number of papers on this topic [133] that are well summarized in a two recent reviews [134,135],... 

C. Singh (1964). Interactions between cationic and anionic compounds of biological importance with special reference to inorganic condensed phosphates and polymeric antibiotics. Ind. J. Chem., 2, 67-81. 

Hydrogen bonds are only rarely an issue in the modeling of small metal complexes. There are, however, some cases where hydrogen bonds are particularly important. For example, when diamineplatinum(II) complexes bind to DNA, hydrogen bonds form between the H(amine) atoms and oxygen atoms on the DNA, and these interactions may be very important in determining the sequence specificity of Pt/DNA interactions[140]. Also, interactions between cationic and anionic complexes will inevitably involve hydrogen bonds and these terms will probably determine whether there is substantial stereoselectivity in the interactions. 

All available experimental results [87] suggest that carbocations are just weakly coordinated to counterion or solvent. For trialkyl and triaryl substituted carbenium ions generated under superacid conditions, this has been demonstrated in a series of X-ray diffraction experiments in particular carried out by Laube and co-workers. [98-102] For example, for the 3,5,7-trimethyl-l-adamantyl cation and its counterion Sb2Fn, the closest C-F distance was measured to be 2.88 A suggesting that interactions between cation and anion are rather weak. [98]... 

A comparison the EW data of the RTlLs with that of conventional solvent systems with respect to the effect of the interaction between cations and anions on the cathodic or anodic limiting potential. 

According to Coulomb s law [cf. Eq. (2-17) in Section 2.6], the interaction between cation and anion can be minimized by increasing either the relative permittivity of the medium or the interionic distance. There are several ways of separating anions from cations and thus increasing the anionic reactivity [643, 842] ... 

Based on the spectra studied, it is concluded that the interaction between cation and anion sublattices in the manganates is mainly electrostatic interaction. 

The influence of the cations and anions has been discussed separately with the solution properties and reactions in the main focus. It has, however, been known over 100 years that anions play a crucial role for the stabilization and coagulation of colloids. More recently, the contribution of anions on the stabilization of particles, biocolloids, and bubbles has received renewed attention. - In these papers, it has been pointed out that there exists a collaborative interaction between cations and anions upon adsorption of one of the complexes from solution. At high concentrations this effect renders the simple indifferent ions specific and selective to each other. It is also seen as a dependency on the acid-base pair chosen for the regulation of the pH. This effect certainly needs to be added as an extension to (correction of) the DLVO theory. However, as shown in this paper, it is just as probable that the anion and cation collaborate during the adsorption and formation of gels and precipitates at the surface. The presence of such mixed phases has been confirmed experimentally, e.g., during the formation of hydroxoapatite in silica gel layers. ... 

Numerous models predict the activity coefficient of individual ions in solution. The one by Debye and Hiickel [8] considers only electrostatic (columbic) interactions between cations and anions in a dilute solution of a single, completely dissociated salt. It is assumed that ion-ion interactions (as opposed to other phenomena such as ion-solvent interactions, ion solvation effects, and variations in the solvent dielectric constant with salt concentration) cause the ion activity coefficients to deviate from 1.0. From a practical point, only the Debye-Hiickel activity coefficient relationship is needed, along with some knowledge of the theory s shortcomings, which restrict its application. For a dilute electrolytic solution containing a binary salt (i.e., a salt with one type each of cation and anion species), the ion activity coefficient from Debye-Hiickel theory is given by... 

In both [PhCNSSN][S3N3] and [PhCNSSN]2[Pt(mnt)2], there are ir out-of-plane interactions between cation and anion, as previously described in Section III, and arising through 77/77 overlap. In order to maximize such overlap, the mean planes of cations and anions in both complexes are approximately coplanar and the twist angle between the phenyl and... 

In both [41][S3N3] (Fig. 7a) and [41][Pt(mnt)2], there are secondary, out-of-plane 77-77 interactions between cation and anion, although they would appear stronger in the former salt (cation-anion separation 3.056 A and 3.5 A, respectively) in agreement with the analogous structures described in Section V.C. ... 

In the solid state structure of [D3S04] [SbF6] (made by using DF in place of HF), the cation has structure 15.52 and there are extensive O—D----F interactions between cations and anions. 

Group vibrations assigned using C-deuteriated ethylenediamine, and various anions. Pd— Pd interactions between cation and anion do not affect vibrational spectra... 

Structural Stability The structural stabihty of different ionic hquids is explained in terms of interactions between cations and anions, as weU as their symmetry. These interactions, and the force between the cations and the anions, lead to changes in the physical properties of the ionic hquids (57). Lengthening the alkyl chain of the cation decreases the symmetry of the cation and increases the van der Waals forces, as it requires more energy for molecular motion (57). Hence, shorter alkyl chains are preferable because of their low viscous properties. The functionahza-tion of the side chain also affects the interaction between the cations and anions, which ultimately changes the physical properties. The hydrogen bonding and the dipole-dipole between the anion and the cation also affect the intermolecular forces and the stability properties (57). 

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