Chromogenic naked-eye detection of copper ion and fluoride

Abstract

A bi-functional colorimetric chemosensor 1, based on julolidine moiety and N-(2-aminoethyl)-5-nitropyridin-2-amine, has been synthesized and characterized. The sensor 1 has proven to be highly selective and sensitive to Cu 2+ with a color change from colorless to yellow in aqueous solution. The sensing mechanism of 1 for Cu 2+ was proposed to be the ligand-to-metal chargetransfer (LMCT), which was explained by theoretical calculations. It was also found that the 1-Cu 2+ complex could be recycled simply through treatment with an appropriate reagent such as EDTA. Importantly, the sensor 1 could be used to detect and quantify Cu 2+ in water samples.Moreover, 1 showed a selective colorimetric response toward fluoride due to the increase in the intramolecular charge transfer (ICT) band by a deprotonation process without any inhibition from other anions such as CH3COOand CN -.

Crystal structure of (E)-9-({[4-(diethylamino)phenyl]imino}methyl)-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-8-ol

“…8-Hydroxyjulolidine-9-carboxaldehyde is a well-known chromophore used in fluorescence chemosensors, and chemosensors with the julolidine moiety are usually soluble in aqueous solutions (Narayanaswamy & Govindaraju, 2012;Maity et al, 2011;Na et al, 2013;Noh et al, 2013). Compounds containing a julolidine group exhibit chromogenic naked-eye detection of copper, zinc, iron and aluminium ions as well as fluoride ions (Choi et al, 2015;Wang et al, 2013a,b;Kim et al, 2015;Jo et al, 2015). There are many reports in the literature on 8-hydroxyjulolidine-9-carboxaldehyde-based Schiff bases and their application as metal sensors (Park et al, 2014;Lee et al, 2014;Kim et al, 2016).…”

“…There are very few examples of similar compounds in the literature and, to the best of our knowledge, the new fluorescent chemosensor for the selective detection of Zn 2+ in aqueous solution, mentioned in the Chemical context section (Choi et al, 2015), has not been characterized crystallographically. A search of the Cambridge Structural Database (CSD, Version 5.37, update May 2016; Groom et al, 2016) gave 121 hits for the julolidine moiety.…”

Crystal structure and DFT study of 8-hydroxy-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinoline-9-carbaldehyde

“…Julolidine is chemically an aniline derivative with two N-alkyl substituents forming rings back to the aromatic ring; the fused rings lock the nitrogen lone-pair of electrons into conjugation with the aromatic ring leading to unusual reactivity. The presence of the julolidine ring system in some molecules makes them useful for chromogenic naked-eye detection of copper, zinc, iron and aluminium ions as well as fluoride ions (Wang et al, 2013;Choi et al, 2015;Kim et al, 2015;Jo et al, 2015). Julolidine dyes exhibit excited-state intramolecular proton transfer (Nano et al, 2015).…”

Crystal structure of 9,9′-{(1E,1′E)-[1,4-phenylenebis(azanylylidene)]bis(methanylylidene)}bis(2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-8-ol)

“…8-Hydroxyjulolidine-9-carboxaldehyde is a well-known chromophore used in fluorescence chemosensors; chemosensors with the julolidine moiety are usually soluble in aqueous solutions (Narayanaswamy & Govindaraju, 2012;Maity et al, 2011;Na et al, 2013;Noh et al, 2013). Compounds containing the julolidine group display chromogenic naked-eye detection of copper, zinc, iron, and aluminium ions as well as fluoride ions (Choi et al, 2015;Wang et al, 2013a,b;Kim et al, 2015;Jo et al, 2015). There are many reports in the literature on 8-hydroxyjulolidine-9-carboxaldehyde-based Schiff bases and their applications as sensors for metal ions (Park et al, 2014;Lee et al, 2014;Kim et al, 2016).…”