Catenane electron exchange

Over the last decade, noncovalent bonding interactions between appropriate Jt-elec-tron-deficient and Jt-electron-rich recognition sites have been exploited in our laboratories for the synthesis of catenanes and rotaxanes. 271 In the example illustrated in Figure 10, the bis(hexafluorophosphate) salt 11-2PF6 was treated 28 with trons-bis(pyridine)ethylene (12) in the presence of the previously formed macrocyclic polyether bis-p-phenylene-34-crown-10 (13). The resulting [2]catenane 14-4PF6 was isolated in 43 % yield after counterion exchange. 

Detailed electron- and energy-transfer studies have been carried out, on the copper(I) complexes, on the demetalated species and, in some cases, on complexes obtained by exchanging the copper center for another cationic metal (Li, Ag" "). The photophysical properties have been studied in different solvents, however, being solvents of similar polarity, the results for different systems can be considered comparable. Time-resolved measurements allowed us to analyze in detail several electron and energy transfer processes occurring in cascade in some of the highly multicomponent catenanes and rotaxanes of the present article. In addition, it has been possible to identify very distinct conformers in solution, some of them containing two chromophores located close to one another and others with remote chromophores. 

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