Calixarene-based PET sensors

Calixarene containing a dioxotetraaza unit, PET-18, is responsive to transition metal ions like Zn2+ and Ni2+. Interaction of Zn2+ with the amino groups induces a fluorescence enhancement according to the PET principle. In contrast, some fluorescence quenching is observed in the case of Ni2+. PET from the fluorophore to the metal ion is a reasonable explanation but energy transfer by electron exchange (Dexter mechanism) cannot be excluded. 

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Fig. 10.15. Calixarene-based PET sensors (PET-17 Aoki I. et al. (1992) J. Chem. Soc., Chem. Commun. 730. PET-18 Unob F. et al. (1998) Tetrahedron Lett. 39, 2951).

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