Heterogeneous solvation model

Heterogeneous dielectric media models have included the developments of Jprgensen et al. [7-9] (reviewed here) and Corni and Tomasi [52,53], Generally, the number of methods for determining frequency-dependent molecular electronic properties, such as the polarizability or first- and second hyperpolarizability tensors of heterogeneously solvated molecules, is very limited. 

Continuum Solvation Models in Chemical Physics 2.10.4 Heterogeneous Dielectric Medium Model... 

The inclusion of the environment effects for non-linear optical (NLO) properties is presented within the PCM (Cammi Mennucci) and the multipolar expansion (Agren Mikkelsen) solvation models. In the first contribution the attention is focused on the connection between microscopic effective properties and macroscopic NLO susceptibilities, whereas in the latter contribution the analysis is extended to treat heterogeneous dielectric media. 

Environmental effects, such as solvation and long-range electrostatic interactions, can be included approximately in a calculation on a an active site cluster model by the use of continuum solvation models, but these cannot fully represent the heterogeneous electrostatic environment in an enzyme.74 An... 

Photoinduced ET at liquid-liquid interfaces has been widely recognized as a model system for natural photosynthesis and heterogeneous photocatalysis [114-119]. One of the key aspects of photochemical reactions in these systems is that the efficiency of product separation can be enhanced by differences in solvation energy, diminishing the probability of a back electron-transfer process (see Fig. 11). For instance, Brugger and Gratzel reported that the efficiency of the photoreduction of the amphiphilic methyl viologen by Ru(bpy)3+ is effectively enhanced in the presence of cationic micelles formed by cetyltrimethylammonium chloride [120]. Flash photolysis studies indicated that while the kinetics of the photoinduced reaction,... 

This contribution contains a section on the energy functional and the response theory of a solvated molecule interacting with a solvent given by either a homogeneous or a heterogeneous dielectric media model. 

In the second chapter, Appleby presents a detailed discussion and review in modem terms of a central aspect of electrochemistry Electron Transfer Reactions With and Without Ion Transfer. Electron transfer is the most fundamental aspect of most processes at electrode interfaces and is also involved intimately with the homogeneous chemistry of redox reactions in solutions. The subject has experienced controversial discussions of the role of solvational interactions in the processes of electron transfer at electrodes and in solution, especially in relation to the role of Inner-sphere versus Outer-sphere activation effects in the act of electron transfer. The author distils out the essential features of electron transfer processes in a tour de force treatment of all aspects of this important field in terms of models of the solvent (continuum and molecular), and of the activation process in the kinetics of electron transfer reactions, especially with respect to the applicability of the Franck-Condon principle to the time-scales of electron transfer and solvational excitation. Sections specially devoted to hydration of the proton and its heterogeneous transfer, coupled with... 

There a been a number of interesting applications of the framework developed in the studies of the simple ions were MD simulations of the quadrupolar relaxation has been performed on counterions in heterogeneous systems. Studies of a droplet of aqueous Na embedded in a membrane of carboxyl groups [54], showed that the EFG was strongly effected by the local solvent structure and that continuum models are not sufficient to describe the quadrupolar relaxation. The Stemheimer approximation was employed, which had been shown to be a good approximation for the Na ion. Again, the division into molecular contributions could be employed to rationalize the complex behavior in the EFG tensor. Similar conclusions has been drawn from MD simulation studies of ions solvating DNA... 

The well-known continuum models and also the microscopic theories of solvation dynamics suggest a close relation between solvation dynamics and DR. This is expressed as tl = (soo/so)td where tl is the longitudinal relaxation time and td is the Debye relaxation time. However, the solvation dynamics of an ion at the protein surface is difficult to understand because of the heterogeneous environment of the protein surface. Therefore, a straightforward application of the continuum model with a multiexponential description of DR is not possible. The continuum theory suggests that at short length scales, the relaxation time is essentially given by the DR time. Therefore, we certainly expect a slow component in the solvation dynamics. 

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