Photophysical and complexing properties of new fluoroionophores based on coumarin 343 linked to rigidified crown-ethers

The photophysical and complexing properties of a series of fluoroionophores based on coumarin 343 linked to monoaza-crown ethers are presented. Aiming to modify the selectivity of the fluorescing probe, the complexing cavity is rigidified by the incorporation of benzo groups. Complexation of alkaline-earth cations (magnesium and calcium) induces marked modifications of the photophysical properties of the probes in acetonitrile and in ethanol, whereas the alkaline cations induce only very weak modifications. The stoichiometry of the complexes is 1:1, except for C343-crown and C343-benzocrown in acetonitrile, where two complexes can be formed with calcium. The results obtained show that rigidification of the complexing cavity improves selectivity, favouring the complexation of Mg2+ and Ca2+ versus Li+. Competition between Mg2+ and Ca2+ has also been studied.