A highly sensitive and selective naked-eye probe for detection of Fe3+ based on a 2,5-bis[3-benzyl-2-methylbenzothiazole]-croconaine

A colorimetric sensor based on 2,3-bis(6-chloropyridin-2-yl)-6-fluoroquinoxaline for naked-eye detection of Iron (III) and its application in real sample analysis

Iron ions are crucial for numerous biological processes, and the levels of these ions have a significant impact on human well-being. Hence, it is essential to identify the level of Iron ions using a suitable technique. A new colorimetric sensor, namely "2,3-bis(6-chloropyridin-2-yl)-6-fluoroquinoxaline" (CF), has been introduced to detect Fe3+ through naked-eye observation. The sensor exhibits remarkable specificity towards Fe3+ compared to other metal ions in aqueous environments. Furthermore, it undergoes a substantial color change from colorless to yellow, which is visible without needing additional equipment. The complex formation was proposed to be in 1:1 ratio based on the Job's plot and molar ratio plot. The maximum sensitivity of CF towards Fe3+ was found at pH 6 to 8. Minimal or negligible interference was noticed from different metal ions in the detection of Fe3+. The binding constant using Benesi-Hildebrand was estimated at 1.434 × 104 M-1. Gibbs free energy was determined -23.728 kJ/Mol. The LOD and LOQ were calculated at 0.378 and 1.26 µM, respectively. The probe CF was utilized to recover Fe3+ in tap water, resulting in recovery percentages ranging from 99.44 to 103.61. This indicates that the CF has the ability to identify Fe3+ in environmental samples.

Highly Selective and Sensitive Visual Detection of Fe3+ using a Simple Quinazoline-Based Colorimetric Sensor

Among the various cations, the Fe3+ ion is one of the most critical transition metal ions in living cells for many cellular functions and enzymatic activities. The decrease or overloading of Fe3+ can lead to different disruptions in humans. Also, Fe3+, highly toxic, is very common in all industrial wastewater. So, the design and synthesis of Fe3+ chelators as high-selective chemosensors are essential for detecting Fe3+. In this paper, 6-(6-bromopyridin-2-yl)benzo[4,5]imidazo[1,2-c]quinazoline (BQ) as a novel colorimetric sensor for sensing of Fe3+ was synthesized and characterized by 1H-NMR, 13C-NMR, IR, and mass spectrometry. The sensing behavior of BQ toward various cations has been analyzed via colorimetric detection and UV-vis spectroscopy. The BQ was observed to have excellent selectivity and sensitivity to the presence of Fe3+ among the tested ions in aqueous media. Interestingly, the BQ can selectively recognize Fe3+ ions with the naked eye via the color change of colorless to yellow. The effect of pH on the stability and absorption of BQ towards Fe3+ was studied. The results of pH studies showed that the absorbance of complex BQ/Fe3+ remains stable between pH 5-10. Moreover, to determine the sensing behavior of BQ to Fe3+, the mole ratio method was carried out. The binding stoichiometry of BQ/Fe3+ was assessed by using Job's plot and indicated the 1:1 binding ratio between BQ and Fe3+. Under the optimal conditions, there was a good linear relationship (correlation coefficient R2 = 0.9886) in Fe3+ concentration in the 58-114 μM range, with a detection limit of 53.39 nM.

The complexometric behavior of selected aroyl-S,N-ketene acetals shows that they are more than AIEgens

Using the established synthetic methods, aroyl-S,N-ketene acetals and subsequent bi- and multichromophores can be readily synthesized. Aside from pronounced AIE (aggregation induced emission) properties, these selected examples possess distinct complexometric behavior for various metals purely based on the underlying structural motifs. This affects the fluorescence properties of the materials which can be readily exploited for metal ion detection and for the formation of different metal-aroyl-S,N-ketene acetal complexes that were confirmed by Job plot analysis. In particular, gold(I), iron(III), and ruthenium (III) ions reveal complexation enhanced or quenched emission. For most dyes, weakly coodinating complexes were observed, only in case of a phenanthroline aroyl-S,N-ketene acetal multichromophore, measurements indicate the formation of a strongly coordinating complex. For this multichromophore, the complexation results in a loss of fluorescence intensity whereas for dimethylamino-aroyl-S,N-ketene acetals and bipyridine bichromophores, the observed quantum yield is nearly tripled upon complexation. Even if no stable complexes are formed, changes in absorption and emission properties allow for a simple ion detection.

1,5-Diaminonaphtalene is a Highly Performing Electron-Transfer Secondary-Reaction Matrix for Laser Desorption Ionization Mass Spectrometry of Indolenine-Based Croconaines

Croconaine dyes are appealing molecules synthesized via the condensation of croconic acid and reactive electron-donating aromatic or heterocyclic systems. Here, matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) investigation of indolenine-based croconaines is presented for the first time. Archetype proton-transfer matrices, such as 2,5-dihydroxybenzoic acid (DHB) and α-cyano-4-hydroxycinnamic acid (CHCA), 9-aminoacridine (9AA) as the protonating/deprotonating matrix, and electron-transfer (ET) secondary-reaction matrices, such as 1,5-diaminonapthalene (DAN) and trans-2-[3-(4-t-butyl-phenyl)-2-methyl-2-propenylidene]malononitrile (DCTB), were investigated. DHB, CHCA, and 9AA generate a mix of odd-electron molecular ions and protonated, sodiated, and potassiated adducts. Among the ET matrices, DAN was found to be capable of directing the ionization process toward the exclusive formation of odd-electron molecular ions M^+• without fragmentation. MALDI tandem MS provides useful structural characterization of croconaine dyes, thus making identification very straightforward for all investigated compounds. Interestingly the fragmentation of bromo-containing croconaines revealed, for the first time, the gas-phase formation of a bromime cation [Br]⁺.