Lumophore-spacer-receptor systems usefulness

The switching efficiency of lumophore-spacer-receptor systems can be improved by using multiple receptor modules. The PET rate is increased in the device when free of guest ions since more than one site can provide the transiting electron. The simplest cases, such as 4, are those where the receptor units are well separated to prevent interdependent ion binding with an interposed lumophore to minimize the lumophore-receptor spacing for maximum PET rates. Besides this statistical effect, receptors may also cooperatively participate in PET. This may be the case in 5 and 6. ... 

Almost all the examples discussed so far use covalent bonds to hold the receptor at a reasonable distance from the lumophore. However, alternative strategies are available. For instance, receptorj selective for the guest ion of interest may be covalently linked to another receptor, which is chosen for its ability to selectively bind a lumophore. This approach has the reward of versatility. Once synthesized, the receptor,-spacer-receptor2 system may be combined with any one of several different lumophores with a range of optical properties. Any enthusiasm this may generate must be tempered because this approach can also have its dangers due to... 

Organic lumophores can also be used in conjunction with receptor,-spacer-receptot2 systems. Aminoalkyl cyclodextrins are particularly suitable in this regard since amines and cyclodextrins show almost mutually exclusive receptor properties. 

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