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Ions in Clusters

The generalized equilibrium reaction in the gas phase between an ion I (g) and solvent molecules S(g) is  [Pg.26]

Alkali metal cations and halide anions have been studied in the earlier years, but alkaline earth metal and divalent transition- and post-transition metal cations have been studied more recently. However, for divalent ions, the second ionization potential ranging from 11.02eV for Sr + through values for Ca, Mg +, Pb +, Mn +, Cr +, Zrf to 20.27 eV for Cu is larger than the ionization potential of the solvent molecules studied—water, ammonia, and methanol 12.61, 10.16, and 10.85eV respectively (except for Ca + and Sr + and water). Therefore, irreversible charge transfer M S (g) M S i(g)-i-S (g) occurs below certain minimal n values that [Pg.26]

Experimental and theoretically calculated values for the clustering energetics are not confined to the solvent S=H20, but for most solvents, only the addition of a single S molecule to an ion has been considered. Ammonia, acetonitfile, and methanol are exceptions to this situation and stepwise solvation of ions has been studied for these solvents (Table 2.7). Competition of such a solvent with water around an ion in a cluster is a readily available experimental method as suggested by Nielsen et al. [32]. [Pg.27]

Apart from the inherent interest in the gas phase ion clusters, the accumulation of solvent molecules around an ion should yield at the limit of very large values of n to a constant value of j H°(S,g). This would be the molar enthalpy of condensation of a solvent molecule into the bulk liquid solvent, because at this limit, the ion has no influence any more on the energetics of the process. Thus  [Pg.27]

TABLE 2.5 The Standard Molar Enthalpies of Stepwise Clustering of Water Molecules Around Ions in the Ideal Gas Phase, j /f°/kJ-mol S atT°=298.15 K [Pg.27]


Mammalian metallothioneins typically bind seven metal ions in cluster structures, with bridging sulfur groups, as seen in the x-ray structure of the Cd5Zn2MT complex (86). It is therefore difficult to develop a simple formation-constant description for the binding of metal ions to MT (87), considering that protonation-deprotonation equilibria of the free protein itself should also be taken into account. However, the usefulness of Table VIII as a guide to the affinity of metal ions for mercapto donor ligands is seen in that the ability of metal ions to... [Pg.141]

The density and survival probability of radicals and ions in clusters... [Pg.289]

The two clusters differ in their metal-binding properties. Mammalian Cd, Zn metallothionein contains four Cd ions in cluster A and two Cd ions and one Zn ion in cluster B. 1157,1159 Calf liver metallothionein contains three Cu ions in cluster B with Cd-displaceable zinc ions in cluster A.1160 Studies on the binding of zinc and cadmium to human liver metallothionein show that binding occurs first in cooperative fashion to cluster A, followed by cooperative binding to cluster B. Incubation of the 7Cd metallothionein resulted in loss of Cd ions from cluster B initially.1161... [Pg.673]

Attempts have been made to observe and experimentally determine the structure of CH5+ in the gas phase and study it in the condensed state using IR spectroscopy,764 765 pulse electron-beam mass spectrometry,766 and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS).767 However, an unambiguous structure determination was unsuccessful. Retardation of the degenerate rearrangement was achieved by trapping the ion in clusters with H2, CH4, Ar, or N2. [Pg.209]

It was demonstrated in this study that Cu ions highly dispersed in matrices that are not active in propene combustion, such as ZrOj and Ga203, are active catalysts for propene reduction of NO to N2 in the lean condition. For the CU-Z1O2 catalysts, it was found that increasing the Cu content resulted in catalysts that were more active in both propene combustion and NO reduction. But the increase in propene combustion activity was faster than NO reduction, thus the resulting efficiency in NO removal decreased. EPR spectra and TPR profiles showed that catalysts with higher Cu contents contained larger fraction of Cu ion in clusters. [Pg.108]

The reactions of large "solvated" ions, with up to lO Ar atoms per cluster were then explored by Dr. Stace. It was clear from this and from the brief presentation by Professor Bernstein that the reactions of ions in clusters differ very significantly from those in the gas phase and that alternative chemical pathways become available with partially solvated species. [Pg.557]

Stuart and Berne [62] have compared the effective two-body TIP4P and a polarizable version based on a fluctuating charge model TIP4P-FQ to solvate either a non-polarizable or a polarizable chloride ion in clusters (H20)nCl for n up to 255. The polarizability model of the ion is based on a Drude oscillator representation. Their simiflations have shown that the chloride ion is solvated at the surface of the cluster for the polarizable model, but the ion is solvated inside the cluster for n < 18 for the non-polarizable model. The explanation for this behaviour is mainly the stronger dipole moment that can be created on water molecules with the polarizable model. Chloride anion polarizability has not been found to have an important effect on the structure of the clusters. [Pg.140]

Fig. 3 Glass transition and density vs mol % ions in clusters for the styrene ionomers. Fig. 3 Glass transition and density vs mol % ions in clusters for the styrene ionomers.

See other pages where Ions in Clusters is mentioned: [Pg.56]    [Pg.259]    [Pg.244]    [Pg.225]    [Pg.91]    [Pg.93]    [Pg.321]    [Pg.26]    [Pg.238]    [Pg.238]   


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