Cation-sensitive fluorescence of anionic polymers bearing naphtho-18-crown-6 units

Changes in the fluorescence intensity of anionic polymers bearing naphtho-18-crown-6 moieties on addition of cations were studied in water at 30 °C. On addition of alkali metal cations, the fluorescence intensity of the polymers decreased sharply for Tl(+) less for Cs(+) and little for Li(+), K(+) and Rb(+). On addition of alkaline earth metal cations, Ba(2+) caused the strongest decrease of the fluorescence intensity of the polymers. The decrease of the fluorescence intensity of the polymers was suggested to be caused by the external heavy-atom effect of the cations bound to the cavity of the crowned naphthalene moiety. The content of the crowned naphthalene units in the polymers affected the cation-dependent fluorescence change. The fluorescence change of the polymers based on the cation complexation competition was also studied.