Experimental and DFT Investigation of a Vitamin B6-Derived Fluorescent Probe for Detection of Al3+ and Ga3+ Ions in a Buffered Aqueous DMSO Solution

A new selective fluorescent probe based on a vitamin B6 derived hydrazone was synthesized and characterized for the detection of Al3+ and Ga3+ ions. The probe’s selectivity and sensitivity were evaluated using UV-Vis, fluorescence, and NMR spectroscopy in a buffered DMSO/water solution, complemented by density functional theory (DFT) calculations to elucidate the electronic structure and coordination modes of the resulting complexes. The probe exhibited a notable “turn-on” fluorescence response upon binding Al3+ and Ga3+, with emission maxima at 466 nm and 477 nm, respectively, and detection limits as low as 48 nM for Al3+ and 33 nM for Ga3+. The probe showed high selectivity for these ions over a wide range of competing cations and anions, forming stable 1:1 complexes with log β′ values of 5.98 for Al3+ and 6.28 for Ga3+. DFT calculations revealed a tridentate coordination mode via the phenolic oxygen, azomethine nitrogen, and carbonyl oxygen, with distinct electronic transitions for each complex, including a ligand-to-metal charge transfer character in the Ga3+ complex. The probe demonstrates reversibility and excellent solution stability, offering a simple and sensitive platform for the environmental and biological monitoring of aluminum(III) and gallium(III) ions.