Triazole-conjugated spiropyran: synthesis, selectivity toward Cu(II), and binding study

Abstract Triazole-conjugated spiropyran was synthesized by Cu(I)-catalyzed azide–alkyne cycloaddition and its metal sensing properties were investigated. Color changes were observed upon the formation of metal complex between the spiropyran and Cu 2+ , which was found to be selective for Cu 2+ ions among Co 2+ , Hg 2+ , Li + , Mg 2+ , Ni 2+ , Zn 2+ , Cd 2+ , and Cu 2+ ions. Moreover, because of the color change, the complex could be detected by the naked eye. An interesting two-stage metal binding mechanism was observed for the sensing process. First, a metal cation brought the two 1,2,3-triazoles together. Second, the Cu 2+ ion was selectively sensed by the conversion of the spiropyran to the merocyanine form.