A dual-functional 8-hydroxyquinoline fluorescent probe for simultaneous detection of solvent microenvironments and...

Reliable detection of trace water in organic solvents is indispensable for maximizing the efficiency and safeguarding the performance of water-sensitive chemical reactions. Herein, we synthesized and characterized a highly emissive organic molecule, 2-(1-butyl-6-(butylamino)-5-methoxy-1H-benzo[d]imidazol-2-yl)quinolin-8-ol (DBIMHQ), from an 8-hydroxyquinoline-benzimidazole combination. The as-prepared DBIMHQ exhibits significant solvatochromic behavior in various solvent systems. Moreover, DBIMHQ exhibited a noticeable red shift in fluorescence and a visible color change (under UV light) in different solvent systems as their polarity increased. The positive solvatochromism was examined through solvent polarity indices like the Lippert-Mataga plot and the ENT parameter. Interestingly, the newly prepared molecule DBIMHQ shows a substantial change in fluorescence in aprotic/protic organic solvents upon the addition of water into the DBIMHQ-solvent system. DBIMHQ exhibited a considerable decrease in the fluorescence intensity upon interaction with less than 1% water content by volume in organic solvents within a short timescale (<30 s). Besides these changes, the DBIMHQ-THF solvent system shows a remarkable spectral shift from 517 nm to 530 nm and a color change from bright green to weak yellow upon the addition of a trace amount (1% v/v) of water. Furthermore, the intermolecular hydrogen bonding interaction between water and the fluorophore DBIMHQ was elucidated through ¹H NMR titration analysis and DFT studies. The practical applicability of DBIMHQ was demonstrated through the quantitative and qualitative analyses of water in raw food materials. In addition, a chitosan-DBIMHQ thin film was developed as a solid support for real-time detection of trace water in organic solvents.