A novel oxazole-based fluorescence sensor towards Ga³⁺ and PPi for sequential determination and application

An innovative Schiff base derivative N'-(4-(diethylamino)-2-hydroxybenzylidene)-5-(naphthalen-1-yl)oxazole-4-carbohydrazide (G2) was designed and synthesized by condensation from 4-(diethylamino)-2-hydrox-ybenzaldehyde and 5-(naphthalen-1-yl)oxazole-4-carbohydrazide. Due to the introduction of Ga3+, G2 expressed an impressive fluorescence change from dysphotic to bright green and a visible color change from colorless to yellow, which could distinguish Ga3+ from the same IIIA group metal (Al3+, In3+), thus it was regarded to be a "turn-on " fluorescence sensor toward Ga3+. The in-situ gained complex G2-Ga3+ without further separation could be acted as a new sensor for PPi through fluorescence quenching. And the complex stoichiometry of G2- Ga3+ was demonstrated to be 1: 2 through Job's plot, which was further confirmed by mass spectrometry titration along with theoretical calculation. Furthermore, G2 had been succeeded in determination of target ions in real water samples and molecular logic gate for Ga3+ and PPi.