Rare Earth Complexes as Luminescent Chemosensors for Cations

3 Rare Earth Complexes as Luminescent Chemosensors for Cations 

Metal ions (such as Zn + or Cu ) at the trace level are often essential to biochemical reactions, for example, in catalysis, transport, or biosynthesis. However, at higher concentrations, accumulation of these ions in an organism can lead to unhealthy interactions such as biochemical redox processes and inhibition of enzyme activity. Therefore, the detection of metal cations is of great interest to many scientists [10,16,18,24]. 

In lOOmMHEPES [Af -(2-hydroxyethyl)piperazine-A-ethanesulfonic acid)] buffer at pH 7.4, the time-resolved emission intensity of Tb + increased upon addition of Zn + from 

0 to 1 equiv. The enhancement of the emission intensity of Tb-13 upon Zn + binding appears to be the result of efficient intramolecular energy transfer from the pyridyl group to the Tb + ion, as shown in Eigure 13.8. Moreover, Tb-13 exhibited a high selectivity for Zn + over other metal ions. 

It is well known that copper ion (Cu +) is able to quench Eu(III) emission. Recently, the Eu(III)-cyclen-p/ien conjugate Eu-1 (Eigure 13.5) has been reported as a luminescent copper sensor. The addition of Cu + to the solution of Eu-1 at pH 7.4 induced the quenching of Eu(III) luminescence at 615nm [36]. 

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