Switchability definition

As Figure 3 illustrates, redox active guests introduce PET processes almost by definition and luminescent on-off switching is the norm. However, the inhibitions outlined in Section 5 have not prevented the designers of switchable luminescent devices from exploring systems which bind redox active guests. The combined forces of inorganic coordination chemistry and supramolecular science have proved to be too attractive in many of these instances. It is to be hoped that some of this effort will filter across to the examination of more on-off systems like 17 and 18. 

We start this section with some definitions. First, we define a diffractive optical element (DOE) as a passive optical element, its properties being either stationary or switchable, with operation based on diffraction or interference of light beams passing through it or being reflected from it. This is a very broad definition and includes a large number of specific subclasses. 

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