A highly selective chemosensor for copper ion based on ICT fluorescence

Simple structural compounds 1 to 3 were synthesized. The presence of Cu2+ resulted in the fluorescence and absorption spectra change of 1 and 2, which indicated that 1 and 2 showed a highly selective response to Cu2+ over other metal ions. However, 3 showed no selectivity for metal ions, which means that the compound could bind with several metal ions, such as, Ni2+, Zn2+, Cd2+, Hg2+, Pb2+, Fe3+, Mg2+, Ca2+, and Co2+, except Cu2+ and Ag+. The different spectral responses were attributed to the difference in binding sites for 1 and 3.