In this paper allosteric interactions are employed to enhance electron transfer in a pseudorotaxane system. Binding of an axial ligand (tbpy) to an electron donating mono-cavity appended zinc porphyrin (ZnP) increases the complexation strength to an electron accepting monosubstituted bipyridine, resulting in a more pronounced electron transfer process after excitation of the zinc porphyrin. Binding constants are presented for this host and different mono-substituted bipyridine guests. the

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... of ZnP at a concentration of 10 À3 M in CDCl 3 / CD 3 CN = 1 : 1 (v/v), according to 1 H NMR measurements.