The fluorescent titration showed that the emission intensity of 1 at 508 nm was almost quenched when 2 equiv of Cu2þ were added. To utilize 1 as a selective sensor for Cu2þ, the effect of competing metal ions was studied. When 1
was treated with 2 equiv of Cu2þ in the presence of 2 equiv of all other metal ions as shown in Fig. 9, no interference was observed, except that Al3þ showed about 25% inhibition. Thus,1 could be used as a selective fluorescent sensor for Cu2þ in the presence of most competing metal ions.