Fluorescent chemosensors from hydrazide derivatives of julolidine

Abstract

Three derivatives of N-acylhydrazone julolidine are synthesized and comparatively investigated for their selectivities as metal ion fluorescent sensors. The compound derived from picolinohydrazide is found to be a "turn-on" fluorescent sensor for Cu2+ in aqueous DMSO media. The mechanistic investigation suggests that Cu2+ promotes the hydrolysis reaction of picolinohydrazide moiety to generate a highly fluorescent compound julolidine-9-carboxaldehyde which has a maximum emission signal at 420 nm. This probe shows an extraordinary selectivity for Cu2+ over other metal ions with a detection limit of 0.1 ppm. Under optimal conditions, the determinations of Cu2+ in real water samples are successfully executed.

In addition, aza crown ether derivatives of julolidine have also been designed for use as metal ion sensors. The synthesis of aza crown ether could be carried out smoothly, but there were many obstacles in the coupling steps of the aza crown ether with the julolidine-9-carboxaldehyde. The desired product could not be obtained even though several different synthesis methods and structural designs were changed. Therefore, this part of the research is presented to illustrate the synthesis planning guidelines in other further works.