Solvation effective coordinate

In a few cases, where solvent effects are primarily due to the coordination of solute molecules with the solute, the lowest-energy solvent configuration is sufficient to predict the solvation effects. In general, this is a poor way to model solvation effects. 

Solvation effects and coordination properties of porphyrins and metalloporphyrins in solutions 98MI19. 

It needs to be pointed out that E values may also be quite sensitive to the nature of the solvent and supporting electrolyte used for an electrochemical study. Apart from solvation effects of the non-specific type, solvent molecules may occupy coordination sites in either the starting complex or the products and hence influence redox behaviour (Fabbrizzi, 1985). Similarly, the nature of the anion present may also strongly influence the redox potential if it has ligating properties (Zeigerson etal., 1982). Because of such effects, caution needs to be exercised in attempting to compare electrochemical data which have not been obtained under similar conditions. 

Solvation Thermodynamics and the Treatment of Equilibrium and Nonequilibrium Solvation Effects by Models Based on Collective Solvent Coordinates... 

S. C. Tucker and D. G. Truhlar, Generalized Bom fragment charge model for solvation effects as a function of reaction coordinate, Chem. Phys. Lett. 157 164 (1989). 

When the apparently penta-coordinated diarsine complexes just described are dissolved in solvents more polar than nitrobenzene, they tend to dissociate into halide ions and bivalent cations, thus becoming 2 1 electrolytes (119). The effect is most marked with the platinum compounds. It has been shown that solvation effects might be less with platinum than with palladium, and so, other things in the equilibria being equal, it can also be concluded that the bonding of further ligands by a square-planar complex is much weaker with platinum than with palladium. Square-planar nickel complexes are of course the most ready to take up further ligands. 

At the next level of approximation, we continue to imagine the solvent to be fully equilibrated to tlie reacting system at every point, but instead of working with the solvated MEP from the gas-phase surface, we find tlie equilibrium solvation patli (ESP) which is the MEP on the fully solvated surface (see Figure 11.1). While both die gas-phase and solvated surfaces are defined entirely in terms of solute coordinates, tlie I iSP may be quite different from the gas-phase MEP because solvation effects may push the patli in directions orthogonal to the gas-phase reaction coordinate (see Figure 11.5). With die ESP in hand, TST (or VTST) analysis may be carried out in the usual way lo obtain a condensed-phase rate constant. 

The quantity 17(f) is the time-dependent friction kernel. It characterizes the dissipation effects of the solvent motion along the reaction coordinate. The dynamic solute-solvent interactions in the case of charge transfer are analogous to the transient solvation effects manifested in C(t) (see Section II). We assume that the underlying dynamics of the dielectric function for BA and other molecules are similar to the dynamics for the coumarins. Thus we quantify t](t) from the experimental C(t) values using the relationship discussed elsewhere [139], The solution to the GLE is in the form of p(z, t), the probability distribution function. 

Whilst such a classification [1, 9] is useful because it indicates the different types of chemical changes which can occur at the metal centres during phase transfer, it oversimplifies the situation in many cases and fails to indicate the importance of the outer sphere coordination chemistry and of solvation effects in general on the free energies of extraction. Alternative classifications of extraction processes which take better account of these have been presented recently by the Moyer Group. [22] The importance of such supramolecular effects in the design of reagents will be stressed in the examples below. 

The 2+/3+ transition in the Marcus model or its successors involves only small Inner Sphere changes in solvation molecule coordinates in the radial direction to and from the ion. Electron transfer under FC or Born-Oppenheimer conditions demands that an activation energy in the outer Continuum should resist one-electron transfer via a continuum inertial term X = (e2/2r )(l/n2 - l/e0) where r is an effective intermediate reactant-product radius. To avoid error, X can be... 

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