New D–A–π-A type solvatochromic dyes for highly sensitive detection of water content in organic solvents and fluoride ion

•Two benzotriazole-based D-A-π-A structured small organic molecules (LM3 and LM4) have been designed and synthesized.•The two dyes exhibited significant fluorescence quenching with the addition of water in organic solvents.•LM4 is an excellent multifunctional fluorescent sensor with great promising application in detecting trace water in organic solvents and fluoride ions. The development of a rapid and sensitive method for the detection of water content in organic solvents and fluoride ion is of great significance. In this study, two benzotriazole-based D-A-π-A structured small organic molecules (LM3 and LM4) bearing triphenylamine as the electron-donating unit (D), 2-(3,4,5-triffuorophenyl)-2H-benzotriazole as the additional electron-withdrawing unit (A), benzene as π spacer (π) and salicylaldehyde or aldehyde as the electron-accepting units (A) have been successfully designed and employed as a fluorescent probe for the detection of water content and fluoride ion. Both dyes show remarkable solvatochromism with large Stokes shift and significant fluorescence quenching with the addition of water in organic solvents. Compared to LM3, LM4 with salicylaldehyde group achieved more effective sensing behavior for water detection with lower limit of detections (0.0012 % for 1,4-dioxane, 0.0323 % for EA and 0.0048 % for THF) due to the stronger hydrogen bonding interaction. In addition, LM4 exhibited a notable fluorescence enhancing response to fluoride ion compared to other anions. The detection limit of 4.8 × 10–7 M was determined with a linear range from 2 to 50 μM. In this regard, LM4 is an excellent multifunctional fluorescent sensor with great promising application in detecting water content in organic solvents and fluoride ion. [Display omitted]