Dihydroquinazolinone based “turn-off” fluorescence sensor for detection of Cu2+ ions

• A “turn-off” type fluorimetric chemosensor for Cu2+ ions is described.
• The detection limit of sensor for Cu2+ ions was 0.1 nM in a mixed aqueous system.
• The complexation has been proven by single crystal X-ray analysis technique.

A strategy for the synthesis of a dihydroquinazolinone derivative, 2-(pyridine-2-yl)-2,3-dihydroquinazolin-4(1H)-one and its application in selective recognition of Cu2+ ions has been developed. The sensor shows “turn-off” type paramagnetic fluorescence quenching towards Cu2+ ions. The binding constant (Ka) of Cu2+ ions with the sensor was found to be 8.02 × 104 M−1 and binding stoichiometry was determined to be 1:1 based on the Job's plot analysis. The sensor can detect up to nanomolar (0.1 nM) level of Cu2+ ions from tap water. The single crystal of the QZP·Cu2+Cl·H2O complex was characterized using X-ray diffraction and the paramagnetic nature of Cu2+ was manifested by electron spin resonance (ESR) spectroscopy.

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