A Novel Benzo[d]Thiazole Derivative as Selective Fluorescent Chemosensors for Al3+ and Its AIE Properties.

A novel benzo[d]thiazole derivative (B31) was synthesized via a green method. Aggregation-induced emission (AIE) behavior was investigated in a dimethyl sulfoxide (DMSO)/water mixture. The solution of B31 exhibited fluorescence emission at approximately 500 nm with maximum intensity observed at 40% water content. B31 functioned as a selective fluorescence chemosensor for Al³⁺ ion with detection limit of 24 nM. In addition, a new complex [Al(B31-2H)(NO₃)] (AlB31) was prepared and characterized by electrospray ionization mass spectrometry (ESI-MS), infrared spectroscopy (IR), and proton nuclear magnetic resonance spectroscopy (¹H NMR) spectra. Notably, the quantum yields of AlB31 complex in DMSO was approximately 60-foldhigher than that of the free B31 ligand, accompanied a significant Stokes shift. Density functional theory (DFT) calculations were performed to rationalize the optical properties of the studied compounds. The weak fluorescence of B31 is likely caused by the rotation of the naphthalene ring around the -CH = N- bond in the S₁ excited state. A plausible photoemission mechanism for the AlB31 complex has also been proposed.