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Protonation Constant; Alkali Cation; Photochemical Property; Alkaline Earth Cation; Concentration Jump
Abstract:
In many biological studies the generation of fast cation concentration jumps without mechanical disturbance of the biological system is of considerable interest. We have recently reported the synthesis of photo-cleavable cryptands 1 and 2 substituted with a 2-nitrophenyl group at one of the cryptand bridges as alkali ion selective ligands (2,3,5). These cryptands are suitable for binding alkali as well as alkaline earth cations (caged-cations) and releasing the complexed cation after a short pulse of UV light, due to the cleavage of the substituted cryptand bridge. This results in a drastical decrease of the stability of the cation/ligand complex (2,5). Cryptands 3 and 4 were synthesized as fast, selective and sensitive indicators for alkali cations in aqueous solution. Fluorescence and cation binding properties of these ligands are discussed.
