A benzothiazole-based receptor for colorimetric detection of Cu2+ and S2− ions in aqueous media

Simple turn-on fluorescent probe for ultrafast and highly selective detection of hydrogen sulfide in aqueous solutions

5H-Benzimidazo[1,2-c]quinazoline-6-thione (BI-QT), was synthesized as a benzimidazole-based probe to detect H2S. BI-QT exhibits a fluorescent "turn-on" response in DMSO/H2O (9:1, HEPES 10 mM, pH 7.4) upon the addition of H2S. The BI-QT probe can determine micromolar (0-600 µM) H2S concentrations in aqueous systems, with a detection limit of 1.12 µM. Interestingly, BI-QT exhibited an ultrafast response to H2S, with maximum intensity achieved almost instantly when exposed to H2S. BI-QT is largely unaffected by pH and responds reliably over the wide 4-11 pH range, which highlights its applicability to various physiological scenarios. UV-vis, fluorescence, and 1H NMR spectroscopic analyses investigated the sensing mechanism. The practicality of the probe was demonstrated using water samples and living cells.

Recent Advances in the Application of 2-Aminobenzothiazole to the Multicomponent Synthesis of Heterocycles

Heterocycles are a vital class of compounds in numerous fields, including drug discovery, agriculture, and materials science. Efficient methods for the synthesis of heterocycles remain critical for meeting the demands of these industries. Recent advances in multicomponent reactions (MCRs) utilizing 2-aminobenzothiazole (ABT) have shown promising results for the formation of heterocycles. The versatility of 2-aminobenzothiazole in this context has enabled the rapid and efficient construction of diverse heterocyclic structures. Various synthetic methodologies and reactions involving 2-aminobenzothiazole are discussed, highlighting its importance as a valuable building block in the synthesis of complex heterocycles. The potential applications of these heterocycles in drug discovery and material science are also explored. Overall, this review provides a comprehensive overview of the current state of research in the field and offers insights into the future directions of this promising area of study. We highlight the potential of ABT as a versatile and sustainable starting material in heterocyclic synthesis via MCRs, with significant implications for the chemical industry.

A novel dual-function probe for fluorescent turn-on recognition and differentiation of Al3+ and Ga3+ and its application

In this study, a novel dual-function probe BMP based on benzothiazole was easily synthesized and characterized through common optical technique. In the system consisting of DMF/H₂O (v/v, 2/3), probe BMP showed azure and blue-green to Al³⁺ and Ga³⁺, respectively. Besides, the binding ratios of BMP to Al³⁺ and Ga³⁺ were determined as 1:1, which confirmed by Job's plot. Furthermore, for Al³⁺ and Ga³⁺, the limit of detection (LOD) was determined to be 1.51 × 10^-6 M and 4.28 × 10^-6 M, respectively. Moreover, it was worth noting that BMP showed good performances in paper colorimetry, cell phone colorimetric identification and cell imaging.

An ESIPT-based fluorescent turn-on probe with isothiocyanate for detecting hydrogen sulfide in environmental and biological systems

A probe with an isothiocyanate group was synthesized and evaluated for its H₂S sensing ability. Upon addition of H₂S, the probe exhibited ratiometric properties during absorption with a red-shift. The probe exhibited fluorescent off-on responses towards H₂S via the ESIPT process, due to the conversion of isocyanate into amine. UV-vis, fluorescence, and ¹H NMR spectroscopic analyses were performed to investigate the sensing mechanism. The probe has a large Stokes shift, short response time, and low detection limit. It can be used to estimate H₂S levels within the range of 0-36 nM. The practical applicability of the probe was demonstrated using water samples and living cells.

An NBD-based fluorescent and colorimetric chemosensor for detecting S2-: Practical application to zebrafish and water samples

A novel 7-nitro-1,2,3-benzoxadiazole (NBD)-based chemosensor BOP ((5-bromopyridin-2-yl)(4-(7-nitrobenzo[c][1,2,5]oxadiazol-4-yl)piperazin-1-yl)methanone) was synthesized. BOP could detect S^2- through fluorescent quenching and colorimetric change. The detection limit was calculated to be 10.9 µM through fluorescence titration. The reaction mechanism of BOP towards S^2- was estimated to be thiolysis of NBD amine, producing the cleavage products, NBD-S^- and BP ((5-bromopyridin-2-yl)(piperazin-1-yl)methanone). The thiolysis was demonstrated by ¹H NMR titrations, ESI-mass analysis and theoretical calculations. Importantly, BOP was able to successfully monitor S^2- in zebrafish and water samples. Additionally, test strips coated with BOP were applied to the in-the-field measurements of S^2-.

Synthetic Approaches to Biologically Active C-2-Substituted Benzothiazoles

Numerous benzothiazole derivatives are used in organic synthesis, in various industrial and consumer products, and in drugs, with a wide spectrum of biological activity. As the properties of the benzothiazole moiety are strongly affected by the nature and position of substitutions, in this review, covering the literature from 2016, we focus on C-2-substituted benzothiazoles, including the methods of their synthesis, structural modification, reaction mechanisms, and possible pharmacological activity. The synthetic approaches to these heterocycles include both traditional multistep reactions and one-pot atom economy processes using green chemistry principles and easily available reagents. Special attention is paid to the methods of the thiazole ring closure and chemical modification by the introduction of pharmacophore groups.

A benzothiazole-based fluorescent and colorimetric probe for the detection of ClO- and its application to zebrafish and water sample

A benzothiazole-based fluorescent and colorimetric chemosensor BZD ((E)-2-(benzo[d]thiazol-2-yl)-5-((4-(diethylamino)-2-hydroxybenzylidene)amino)phenol) was applied for detecting ClO^-. BZD showed fluorescence quenching and color variation for ClO^- via oxidative reaction between ClO^- and the imine bond. It could effectively detect ClO^- over various competitive analytes. Detection limit for ClO^- was calculated to be 1.74 μM by fluorescent method and 16.44 μM by colorimetric one, respectively. Additionally, BZD could be utilized for sensing ClO^- in zebrafish, real water sample and paper strip. The photophysical characteristics and sensing mechanism of BZD to ClO^- were studied by fluorescent and UV-visible spectroscopy, NMR titration, and ESI-mass spectrometry.

Real time sensor for Fe3+, Al3+, Cu2+ & PPi through quadruple mechanistic pathways using a novel dipodal quinoline-based molecular probe

A quinoline-based small molecular probe, H₂L was designed, synthesized and characterized by different spectroscopic methods. It was utilized as a multi-responsive probe for the detection of Fe³⁺, Al³⁺, Cu²⁺ and PPi. It showed very selective instant turn-on fluorimetric response towards Fe³⁺and Al³⁺ with a detection limit in nanomolar range. Solutions of H₂L containing Fe³⁺ or Al³⁺ could sequentially sense PPi by a turn-off mechanism. Also, H₂L could determine the presence of Cu²⁺ very selectively among a series of other metal ions by a sharp change in colour. Detection of Cu²⁺ through colorimetry was further investigated by systematic UV-Vis studies and the potential of H₂L to act as a potential colorimetric sensor for Cu²⁺ was suitably established. Filter-paper strip experiments were conducted to demonstrate the practical utility of the proposed sensor. Potential applications of H₂L as a sensor for pH in the acidic range has also been explored.

An Acylhydrazone-Based Fluorescent Sensor for Sequential Recognition of Al3+ and H2PO4. MATERIALS (BASEL, SWITZERLAND) 2021;14:6392. [PMID: 34771920 PMCID: PMC8585233 DOI: 10.3390/ma14216392]

A novel acylhydrazone-based fluorescent sensor NATB was designed and synthesized for consecutive sensing of Al3+ and H2PO4-. NATB displayed fluorometric sensing to Al3+ and could sequentially detect H2PO4- by fluorescence quenching. The limits of detection for Al3+ and H2PO4- were determined to be 0.83 and 1.7 μM, respectively. The binding ratios of NATB to Al3+ and NATB-Al3+ to H2PO4- were found to be 1:1. The sequential recognition of Al3+ and H2PO4- by NATB could be repeated consecutively. In addition, the practicality of NATB was confirmed with the application of test strips. The sensing mechanisms of Al3+ and H2PO4- by NATB were investigated through fluorescence and UV-Visible spectroscopy, Job plot, ESI-MS, 1H NMR titration, and DFT calculations.