Photoregulation of Metal Ion-Adsorbability of Photoresponsive Cellulosic Chelate Polymer.

A cellulosic derivative (Cell-ox-sp) containing both chelating functional 8-hydroxyquinoline (ox) and photoresponsive spiropyran (sp) moieties was synthesized and photoregulation of metal ion-adsorption of Cell-ox-sp was examined. Reaction of powdered cellulose with 5-chloromethyl-8-hydroxyquinoline gave cellulosic derivatives with degree of substitution (DS) by ox up to 1.1, and subsequent reaction of the products with a spiropyran derivative containing carboxyl group did Cell-ox-sp with DS by sp of about 0.5. In the reaction sequence, metal ion- adsorption of the each product increased from cellulose to Cell-ox and considerably decreased from Cell-ox to Cell-ox-sp. Under irradiation with UV light, Cu2+- adsorption of Cell-ox-sp considerably increased and under subsequent irradiation with visible light it decreased as it had been before. These substantial changes in Cu2+- adsorption may suggest that ox moiety and merocyanine type sp moiety yielded with UV light irradiation co-operatively adsorbs Cu2+. Adsorption of Zn2+ showed similar behaviors under irradiations with UV light and with subsequent visible light, but the extent of the change was lower than that for Cu2+. These results show that metal ion-adsorption of Cell-ox-sp may be photoregulated under irradiation with UV light and visible light, possibly selectively in respect to ion species.