Efficient Colorimetric Fluoride Anion Sensor Based on π-Conjugated Carbazole Small Molecule

Abstract

The ability to detect fluoride anions with high selectivity and sensitivity by using the naked eye is crucial yet challenging. In this study, a novel, simple conjugated organic dye, N-tert-butyldimethylsilyl-3,6-diiodocarbazole (CA-TBMDS) was developed and used for the first time as a colorimetric sensor for fluoride. CA-TBMDS was found to be a highly sensitive fluoride chemosensor, with a detection limit as low as 3 × 10−5 M. The reaction of CA-TBMDS with fluoride anions in a tetrahydrofuran solution resulted in a color change from colorless to yellow under ambient light, which can be discriminated by the naked eye. The sensor operated via intermolecular proton transfer between the amide units and the fluoride anion, as confirmed by proton nuclear magnetic resonance titration. CA-TBMDS is not only highly sensitive to fluoride anions, but also exhibits high sensitivity in the presence of various ions. This work demonstrates that N-butyldimethylchlorosilane-based organic dyes have prospective utility as a type of fluoride anion chemosensor.

Colorimetric fluoride detection in dimethyl sulfoxide using a heteroleptic ruthenium(ii) complex with amino and amide groups: X-ray crystallographic and spectroscopic analyses

“…2b ). The combination of conformations of the two Hdpa ligands in 1 2+ has also been observed in [Ru(bpy)(Hdpa) 2 ](ClO 4 ) 2 , 18 but not in the starting complex cis -[RuCl(dmso- S )(Hdpa) 2 ] + (P1 + ). 29 Each Hdpa ligand in P1 + captured a monodentate ligand, Cl, or a methyl group of the dmso- S ligands using two pyridyl groups, resulting in both NH groups being close to each other ( syn -NH conformation, Fig.…”

“…Both angles were consistent with those of the Hdpa ligand in previously reported Ru( ii )–Hdpa complexes (25.9–48.2°). 18,29,39,40 The difference between the two dihedral angles is likely caused by steric interactions between H 2 pia and the two Hdpa ligands. The N2 atom of the NH group in Hdpa( N 1, N 3) established contact with the O1 atom of H 2 pia (N2⋯O1 = 3.036 Å; Fig.…”

“…Moreover, the dihedral angle for the other Hdpa( N 4, N 6) was significantly smaller than that in the chloride salt (15.8° and 29.9°, respectively), and smaller than previously reported Ru( ii )–Hdpa data (25.9°–48.2°). 18,29,39,40 Generally, the bent conformation of Hdpa cuts off a π-conjugated system between two pyridyl groups in the Hdpa ligand. However, the smaller dihedral angle of Hdpa( N 4, N 6) indicated that this Hdpa possessed the π-conjugated system of the entire Hdpa ligand, similar to a coordinated bpy ligand.…”

“…However, the color of [Ru(Hdpa) 3 ] 2+ , in which the Hdpa ligand is formed as a bent six-membered chelate ring, is yellow. 18 Therefore, the intense dark brown color of the fluoride salt suggests that the π-conjugated system of the entire Hdpa ligand was extended and stabilized.…”

Evaluation of naked-eye sensing and anion binding studies in meso-fluorescein substituted one-walled calix[4]pyrrole (C4P)

“… 48 Quite recently, a small molecule, N -tertbutyldimethylsilyl-3,6-diiodocarbazoles a conjugated organic dye, was design, constructed and employed as a selective fluoride colorimetric sensor by Zheng's research group. 49 The limit of detection (LOD) for this system was found to be 3 × 10 −5 M. Notably, in the year of 2023, our research group has also reported a valuable fluorescein functionalized dipyrromethane (DPM) based chemosensor for the selective detection of fluoride, phosphate and acetate ions over various other tested anions. 50 …”