Photo-induced Electron Transfer PET Process

A + B (reductant nature of A and the process is oxidative electron transfer) 

Both these oxidative and reductive electron transfer processes are represented in molecular orbital interactions (Eig. 6.15) 

This photo-induced electron transfer process among the molecules may be utilized as fluorescence switching. A fluorophore having a macrocyclic unit, on irradiation 

The principle of PET process with potassium cation (K ) sensor can be explained as follows. Excitation of the fluorophore causes the promotion of one electron from the HOMO to the LUMO. It enables the flow of one electron from the HOMO of donor macrocyclic unit to fluorophore, resulting in quenching of fluorescence. On binding with cation, the HOMO of the macrocyclic unit is of lower energy than that of fluorophore anthracene. Hence, PET is no longer possible and fluorescence quenching is stopped (Eig. 6.17). 

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Included in this volume are six articles devoted to a process which is basic not only in chemistry, but in biology and physics. The intent is to provide a critical review of some topics in photo-induced electron transfer (PET) in order to complement existing works. All articles are concerned with experimental and theoretical aspects of PET in organic chemistry. The interdisciplinary character of PET is already reflected in the preceding volumes of this series as will be so in the following volumes for electron transfer in general. 

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