Ion-responsive fluorescent compounds. 5. Photophysical and complexing properties of coumarin 343 linked to monoaza-15-crown-5

The photophysical and complexing properties of a fluoroionophore consisting of coumarin 343 linked to monoaza-15-crown-5 are reported in acetonitrile and ethanol. The amide link between the coumarin and the crown precludes pH sensitivity of the tertiary amine bridging group. Upon complexation by calcium and magnesium cations, the photophysical properties undergo marked changes, whereas the effects are insignificant or very weak with alkali metal ions. I.R. spectra were recorded in deuterated acetonitrile in order to unravel the participation of the carbonyl groups in the complexation. The stoichiometry of the complexes is 1:1 apart from the case of complexation with calcium in acetonitrile where two complexes can be formed. The stability constants of the complexes were determined in acetonitrile and ethanol.