facilely synthesized. The binding of Cu(2+) with nitrogen atom of CN moiety in these three compounds can inhibit the photo-induced electronic transition process and induce the ratiometric-absorption and fluorescent OFF-ON response to Cu(2+). Whereas the employment of benzo-15-crown-5 moiety in FBC as additional binding platform for Cu(2+) not only amplifies the fluorescent enhancement of FBCvia preventing