Pseudo-macrocyclic systems

Fig. 3 Photoregulation of polymer/pseudo-macrocycle interconversion in a 9 (n = 3) + H3N+-(CH2)6-NH3 system.

The approaches to heterometaUic systems outlined above all rely upon coordination chemistry, whether to a metal ion or a nanoparticle surface. Supramolecular interactions can also play a role in assembling heterometaUic systems. For instance, Sambrook et al. prepared a pseudo-rotaxane (18) templated around a chloride ion (Fig. 9) in which lanthanide ions are bound to the thread while a luminescent rhenium complex is bound to the macrocycle component [49]. Thus there is no direct link between the donor chromophore and the lanthanide ion, and Dexter exchange is not viable in the absence of bonds enforcing Forster energy transfer. This extreme of behaviour helps to rationalize the behaviour of more conventionaUy... 

Lariat ethers are a class of compounds that contain a single side arm attached to a macrocycle, often by the nitrogen atom of an azacrown. This side arm is flexible (as in a podand) but contributes to the envelopment of the guest cation in a three-dimensional array, as in the cryptands, while the macrocycle exerts stronger complexation than in podand systems. The pseudo-podand arm comes over the face of the macrocycle and binds to the cation that has been encapsulated within the host, as demonstrated in Figure 2.4. 

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