Recognition of dihydrogen phosphate ions using the cadmium complex of 2-pyridine-1H-imidazo[4,5-b]phenazine: utilization of the mechanism of twisted intramolecular charge transfer, long wavelength emission

Abstract

A long wavelength emission fluorescent and colorimetric chemosensor with high selectivity for H2PO4− ions was designed and synthesized according to the twisted intramolecular charge transfer (TICT) mechanism. The sensor bears a 2-pyridine-1H-imidazo[4,5-b]phenazine and Cd2+ metal complex, which showed brilliant fluorescent and colorimetric response for H2PO4− anions in aqueous solution. The detection limit of the sensor towards H2PO4− is 2.8 × 10−6 M, and other anions, including F−, Cl−, Br−, I−, AcO−, HSO4−, ClO4− and CN−, had nearly no influence on the probing behavior. The test strips based on the 2-pyridine-1H-imidazo[4,5-b]phenazine and Cd2+ metal complex (S2–Cd) were fabricated, which could act as convenient and efficient H2PO4− test kits.