Frequency dependence of microwave-assisted electron-transfer chemical reactions

In this paper, the electron transfer reactions in the microwave field are studied. A classical theory is developed for a mix of reagents and polar frequency-dispersive and lossy solvent filling vessels excited by microwaves. These reactors are described by a system of non-linear partial self-consistent differential equations for non-stationary microwave field, heat and liquid dynamics, and chemical molecular kinetics. A particular solution of this system is considered for the isothermic electron-transfer reactions in the microwave field varying its frequency with the calculation of the normalised Marcus rate coefficient. It is found that for the small normalised reaction free energy, the chemical reactions are supported by microwaves in a wide frequency band with an increased value of the exponent in the Marcus rate coefficient. At higher values of this energy, these reactions are driven only by conventional microwave heating. The restrictions for the given theory are reviewed, and further experimental and semi-classical and quantum-mechanical studies are found essential for practical applications of these findings.