Sulfa-Drug-Functionalized Schiff Bases in the Selective Detection of Erythromycin

In this study, selective detection of erythromycin in aqueous solution was achieved by using sulfa-drug-based Schiff bases as fluorescent probes. The detections were performed by simple imines synthesized in a single-step condensation of sulfa drugs, namely sulfadiazine or sulfamethazine, with 4-dimethylamino cinnamaldehyde. The portions from the sulfa drugs present in each probe had played the key role in guiding the selectivity in fluorescence detection by controlling the twisted intramolecular charge transfer (TICT) emission. Theoretical studies have suggested the role of the O-H···π interaction in the selective detections. A cocrystal of sulfadiazine with cinnamaldehyde was characterized during the course of this study; it was not useful for the detection of erythromycin. It was also found that the corresponding Schiff base of aniline and 4-dimethylamino cinnamaldehyde was not selective to make a distinction of erythromycin from other drugs by fluorescence changes. The detection limit for the selective detections of the Schiff base probe of the respective Schiff bases, namely, with sulfadiazine, was 134.5 nM, and with sulfamethazine, it was 180 nM. These limits were comparable in sensitivity to the nanomaterials-based detections reported in the literature. The advantages of the present systems are an easy method of preparation, aqueous stability, the use of benign commercial drugs as probe precursors, and performance at neutral conditions in aqueous medium.