A new fluorescence probe for trace metal ions: Cation-dependent spectroscopic properties

The fluorescence behavior of a new bipyridyl ligand, 2,2-bipyridyl-3,3-diol (BPDO), was studied as a function of the metal ion complexed. At pH 7.6, the fluorescence of BPDO is strongly decreased by complexation to Cu(II), but binding to Zn(II) leads to an increase in fluorescence intensity. Time-resolved fluorescence measurements suggest that in the case of Cu(II), a nonfluorescent complex is formed, whereas in the presence of Zn(II), a new, longer decay component appears.