Selective energy transfer model

Keywords compensation effect, isokinetic effect, Rochow synthesis, transition metal silicide phases, selective energy transfer model... 

We would like to emphasize that this attempt to ply the selective energy transfer model to our results does not mean that we reject other concepts for interpreting the compensation effect. 

Summary Both in the Rochow synthesis of methylchlorosilanes and in the reaction of transition metal silicides with HCl, catalytic reactions of silicon, bound as metal silicide, with gaseous reactants are involved. With both reactions, the kinetic parameters ko and Ea exhibit consequent compensation effects, with the isokinetic temperature positioned within the range of reaction temperatures investigated. In this paper, we ply the model of selective energy transfer fiorn the catalyst to adsorbed species to the kinetic data. With Rochow synthesis Si-CHs rocking frequencies, and with hydrochlorination of silicides Si—H vibration frequencies could correspond to the isokinetic temperatures observed. An interpretation in terms of accessibility of the reactive silicon atom to reactant molecules is given. 

Nowadays, most reaction center models carry suitable antenna pigments and acceptor groups and in effect are photosystem models. A typical example for a state-of-the-art system that incorporates many aspects of a photosystem consisted of a boron dipyrrin covalently linked to a zinc(II) porphyrin, which carried a suitably modified C60 derivative as axial ligand. Selective excitation of the boron dipyrrin as antenna pigment resulted in energy transfer to a zinc(II) porphyrin followed by electron transfer to the acceptor109. 

In Tsang s evaluations the pressure-dependent factors in the expression for the rate constant are handled differently [45]. Using the RRKM model a factor governing the pressure dependence is calculated and presented in tables as a function of the energy transferred per collision. The user may then select a typical value for this energy for the collision partners involved and read the pressure-dependent factor from the tables. Satisfactory application depends on the ability to select the correct energy transferred which may be derived from experimental data on the particular reaction concerned but, more often, may have to be estimated from data on analogous reactions which, usually, are quite limited. 

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