Photophysics of 1,3-alternate Calix[4]arene-crowns and of their Metal Ion Complexes: Evidence for cation-p interactions in solution

The photophysical properties of the family of calix[4]arene-crowns and of their metal complexes are reported here for the first time. Among different observed perturbations, addition of alkali metal ions causes monitorable, and sometimes pronounced, changes in fluorescence intensities and in the wavelength maxima of the hosts. All together, the observed results strongly suggest that the cation-π interactions play a major role in tuning the luminescence properties of the host. The utility of photoluminescence spectroscopy for the determination of association constants between calixarene derivatives and metal ions is also demonstrated.