N-hydroxypropyl substituted 4-hydroxynaphthalimide: Differentiation of solvents and discriminative determination of water in organic solvents

A naphthalimide-based fluorophore (HONIOH) was designed by introducing a hydroxy unit into the 4th position of the aromatic core and a hydroxypropyl unit into the N-imide site. Photophysical properties of HONIOH were highly dependent on solvents, which was ascribed to the excited state proton transfer (ESPT) coupled with intramolecular charge transfer (ICT) mechanism. Further studies demonstrated that HONIOH can be used to recognize N, N-dimethylformamide (DMF) qualitatively and differentiate methanol from ethanol. Three control compounds were synthesized, their photophysical properties were investigated in various solvents, and experimental results revealed that hydroxyl and hydroxypropyl units contribute to the solvents differentiation ability of HONIOH. In addition, HONIOH was successfully applied as a colorimetric, fluorescent probe for the discriminative detection of trace water in organic solvents, such as fluorescence turn-on response accompanied by fluorescent color changes from light yellow to purple in DMF, and fluorescence turn-off response and blue to yellow fluorescent color changes in acetonitrile, tetrahydrofuran, and acetone. We believe that N-substituted 4-hydroxynaphthalimide derivatives may find widespread applications in chemical and biochemical sensing and imaging.

Covalent organic frameworks as a sensing platform for water in organic solvent over a broad concentration range

A highly crystalline covalent organic frameworks (COFs) formed by condensation reaction between 1, 3, 5-tris (4-aminophenyl) benzene and 4, 4'-biphenyldicarboxaldehyde is utilized as a sensing platform for water in organic solvent over a broad concentration range. The resulting COFs exhibits brilliant fluorescence in various organic solvents such as methanol, DMF, acetonitrile and ethanol, moreover its fluorescence intensity has a significant and rapid response to the content of water in organic solvent over a broad concentration range. The broadest sensing range is achieved over 7%-70% (v/v) for water in DMF, and the lowest limit of detection is 0.042% (v/v) for water in methanol among the investigated organic solvents. The superior properties of the sensing platform expand the application ranges of COFs and endow the resulting COFs with a great prospect in practical applications for highly efficient detecting water in organic solvent.