SYNTHESIS AND PHOTOPHYSICAL STUDY OF 4-(N-MONOAZA-15-CROWN-5) STILBENES FORMING TICT STATES AND THEIR COMPLEXATION WITH CATIONS

Three new 4-(N-monoaza-15-crown-5)Stilbene derivatives (DS-Crown, DCS-Crown and PDS-Crown) were synthesized in order to study their spectroscopic properties in connection with the complexation of cations. The three fluoroionophores had almost identical photophysical properties as their counterparts, with a dimethylamino group instead of the macrocycle, but upon complexation by alkali and alkaline-earth metal ions, they showed hypso and hypochromic shifts of the absorption spectrum and a solvent-dependence of the fluorescence: particularly the p-phenyl derivative (PDS-crown) complexed with Ca2+ in n-BuCN led to a dual fluorescence ascribed to an equilibrium, in the excited state, between the complexed ligand involving the nitrogen of the chromophore, as in the ground state, and the cation-ligand separated by the solvent where an additional molecule of n-BuCN entered into the coordination sphere of Ca2+ substituting for the aromatic nitrogen-cation interaction.