SENSING OF TRANSITION-METALS THROUGH FLUORESCENCE QUENCHING OR ENHANCEMENT - A REVIEW

A series of fluorescent sensors for transition metal ions were synthes ized by linking a light-emitting subunit, anthracene, to a polyaza che lating subunit, either a dioxotetraamine or a tetraamine. Sensing of t he divalent cations Cu-II, Ni-II and Zn-II was investigated through sp ectrofluorimetric titrations in acetonitrile-N mater (4:1) solutions, The selective recognition of Cu-II and Ni-II among other transition an d non-transition metal ions is signalled through full quenching of flu orescence; discrimination between the two ions can be achieved by perf orming titrations at controlled pH. The system containing the tetraami ne fragment, whose interaction with Cu-II and Ni-II induces fluorescen ce quenching, is also sensitive to Zn-II, but in this case the recogni tion is signalled-through a fluorescence enhancement.