receptor
1 showed a significant emission upon excitation at 420 nm.
Treatment with Al3þ resulted in a large increase in intensity with a
red shift from 508 nm to 531 nm, while upon addition of Cu2þ, the
fluorescence intensity of 1 was completely quenched. As a result,
the fluorescence color of 1 changed from green to yellow for Al3þ
and from green to colorless for Cu2þ.