A novel quinoline derivative as dual chemosensor for selective sensing of Al3+ by fluorescent and Fe2+ by colorimetric methods

A Novel AIE-Active Salicylaldehyde-Schiff Base Probe with Carbazole Group for Al3+ Detection in Aqueous Solution

A donor-acceptor Schiff-base fluorescent probe BKS with chelation enhanced fluorescence (CHEF) mechanism was designed and synthesized via benzophenone(Acceptor), salicylaldehyde and carbazole(Donor) for Al3+ detection, which exhibited typical aggregation-induced emission (AIE) characteristic. BKS probe could provide outstanding selectivity to Al3+ with a prominent fluorescence "turn-on" at 545 nm in a wide pH range from 2 to 11. By the Job's plot, the binding stoichiometry ratio of probe BKS to Al3+ was determined 1:1. The proposed strategy offered a very low limit of detection at 1.486 µM in THF/H2O(V/V = 1:4, HEPBS = 10 mM, pH = 7.40), which was significantly lower than the standard of WHO (Huang et al., Microchem J 151:104195, 2019)-(Yongjie Ding et al., Spectrochim Acta Mol Biomol Spectrosc 167:59-65, 2021) guidelines for drinking water. BKS probe could provide a wider linear detection range of 50 to 500 µM. Furthermore, the probe could hardly be interfered by other examined metal ions. The analysis of Al3+ in real water samples with appropriate recovery (100.72 to 102.85) with a relative standard deviation less than 2.82% indicated the accuracy and precision of BKS probe and the great potential in the environmental monitoring of Al3+.

Nitroquinolone Fused Salicyl and Naphthyl Hydrazone Fluorescent Probes for the Detection of Fe3+and Pb2+ Ions

The application of quinolones stretches over a large umbrella of medicinal field as well as chemosensor due to the presence of privileged heterocyclic aromatic rig system. Salicyl and Naphthyl Hydrazide motifs are also established fluorophore groups. Therefore in this work, we have designed and synthesized Salicyl hydrazide (3a-c) and naphthyl hydrazide fused nitroquinolones (5a-c) investigated for their fluorescent behaviour. Preliminary UV- absorption studies were carried out and the metal selectivity were examined with various metal ion. Among them, it was found that compound 3a was selective towards Fe3+ ions (λex = 330 nm, 1:1 DMF:H2O at pH = 7.4 in HEPES Buffer medium). 3a shows decrease emission intensity in presence of Fe3+ ions. Compound 5a shows enhancement in fluorescence intensity upon addition of Pb2+ ion (λex = 280 nm, 1:1 DMF:H2O at pH = 7.4 in HEPES Buffer medium). Further, the concentration dependence, competitive binding and EDTA reversibility were studied for selected compounds towards the respective cations selectivity. Jobs plot analysis indicate that 1:1 binding of 3a with Fe3+ ion (Ka = 3.17 x104M-1 and Limit Of Detection (LOD) = 5.1 × 10-7 M) whereas 5a showed 1:2 binding mode with Pb2+ ions (Ka = 2.14 × 106 M-1 and Limit Of Detection (LOD) = 2.613 × 10-9 M). Density Function Theoretical studies were performed as support for the experimental results.

Colorimetric and Fluorometric N-Acylhydrazone-based Chemosensors for Detection of Single to Multiple Metal Ions: Design Strategies and Analytical Applications

The development of optical sensors for metal ions has gained significant attention due to their broad applications in biology, the environment, and medicine. Colorimetric and fluorometric detection methods are particularly valued for their simplicity, cost-effectiveness, high detection limits, and analytical power. Among various chemical probes, the hydrazone functional group stands out for its extensive study and utility, owing to its ease of synthesis and adaptability. This review provides a comprehensive overview of N-acylhydrazone-based probes, serving as highly effective colorimetric and fluorometric chemosensors for a diverse range of metal ions. Probes are categorized into single-ion, dual-ion, and multi-ion chemosensors, each further classified based on the detected metal(s). Additionally, the review discusses detection modes, detection limits, association constants, and spectroscopic measurements.

A Dual-target Fluorescent Chemosensor for Detecting Indium (III) and Hypochlorite with High Selectivity

A dual-target fluorescent chemosensor BQC (((E)-N-benzhydryl-2-(quinolin-2-ylmethylene)hydrazine-1-carbothioamide) was synthesized for detecting In3+ and ClO-. BQC displayed green and blue fluorescence responses to In3+ and ClO- with low detection limits (0.83 µM for In3+ and 2.50 µM for ClO-), respectively. Importantly, BQC is the first fluorescent chemosensor capable of detecting In3+ and ClO-. The binding ratio between BQC and In3+ was determined to be a 2:1 through Job plot and ESI-MS analysis. BQC could be successfully utilized as a visible test kit to detect In3+. Meanwhile, BQC showed a selective turn-on response to ClO- even in the presence of anions or reactive oxygen species. The sensing mechanisms of BQC for In3+ and ClO- were demonstrated by 1 H NMR titration, ESI-MS and theoretical calculations.

Synthesis and application of hypochlorite mediated acylhydrazone fluorescence probes

Hypochlorous acid (HClO/ClO- ) is one of the important reactive oxygen species (ROS). It acts as a second signaling molecule within and between cells and is an indispensable active molecule in living organisms to regulate physiological and pathological processes. In this article, two fluorescent probes (PTF and PTA) for highly selective fluorescent recognition of ClO- were successfully synthesized based on the ICT mechanism by condensing phenothiazines with two hydrazides via the hydrazide structure (). PTF can identify different concentrations of ClO- in two steps. Due to its ClO- two site recognition, the probe exhibited good selectivity (specific recognition of ClO- over a wide concentration range), a fast time response (rapid recognition in seconds), a sufficiently low detection limit (3.6 and 11.0 nM), and large Stokes shifts (180 and 145 nm). Furthermore, the recognition of ClO- by contrasting probes with different substituents exhibited different fluorescence changes of ratiometric type and turn-off. PTF successfully achieves the detection of exogenous and endogenous ClO- in aqueous solution and living cells.

A New Azo-Schiff Base Dual-mode Chemosensor: Colorimetric Detection of Cobalt Ions and Fluorometric Detection of Aluminum Ions in Aqueous Ethanol Solution

A new Azo-Schiff base ligand (H₂L) was designed and synthesized as a cation chemosensor. The chemosensor H₂L as dual chemosensor showed selective fluorescence recognition of Al³⁺ with a noticeable fluorescence enhancement and colorimetric detection of Co2 + in aqueous ethanol solution. The H₂L exhibits a linear response toward Al³⁺ ions in the concentration range of 1.91 × 10^-8 M to 4.8 × 10^-6 M with a limit of detection of 1.91 × 10^-8 M. The sensing mechanism of sensor H₂L toward Al³⁺ was investigated by 1H NMR and IR spectroscopies. Fluorescence switch based on the control of EDTA and Al³⁺ proved H₂L could act as a reversible chemosensor. The molecular structure of [NiL] complex has been determined by X-ray crystallography.

Elastase inhibitory activity of quinoline Analogues: Synthesis, kinetic mechanism, cytotoxicity, chemoinformatics and molecular docking studies

Herein, we have synthesized quinoline united various Schiff base derivatives (Q1-Q13) and systematically characterized them using diverse analytical practices such as ¹H NMR, ¹³C NMR, FT-IR and LC-MS respectively. All of the target compounds that have been synthesized were tested for elastase inhibition, and the findings were compared to the standard drug oleanolic acid. Among the entire series, compound Q11 (IC₅₀ = 0.897 ± 0.015 µM) exhibit most promising elastase inhibitory activity than oleanolic acid (Standard) having an IC₅₀ value of 13.426 ± 0.015 µM. Also, the utmost effectivecompound Q11 was used for kinetic mechanism investigation based on in-vitro data, from which it has been concluded that compound Q11 inhibits elastase competitively. Furthermore, utilizing the MTT test approach, the most effective compounds were assessed for cytotoxicity on B16F10 melanoma cells. From the cytotoxicity experiment, the most potent compound did not display any hazardous response against B16F10 melanoma cells despite being treated at high concentrations. Additionally, the molecular docking study was settled to govern the binding interaction pattern among an enzyme and inhibitors.

a Versatile Schiff Base Chemosensor for the Determination of Trace Co2+, Ni2+, Cu2+, and Zn2+ in the Water and Its Bioimaging Applications

In this work, a simple and versatile Schiff base chemosensor (L) was developed for the detection of four adjacent row 4 metal ions (Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺) through colorimetric or fluorescent analyses. L could recognize the target ions in solutions containing a wide range of other cations and anions. The recognition mechanisms were verified with a Job's plot, HR-MS assays, and ¹H NMR titration experiments. Then, L was employed to develop colorimetric test strips and TLC plates for Co²⁺. Meanwhile, L was capable of quantitatively measuring the amount of target ions in tap water and river water samples. Notably, L was used for imaging Zn²⁺ in HepG2 cells, zebrafish, and tumor-bearing mice, which demonstrated its potential biological applications. Therefore, L can probably serve as a versatile tool for the detection of the target metal ions in environmental and biological applications.

A novel quinoline derivative as a highly selective and sensitive fluorescent sensor for Fe3+ detection

In this research, a novel selective and sensitive fluorescent sensor for detecting Fe³⁺ was designed and synthesized; it revealed an obvious fluorescence quenching effect upon addition of Fe³⁺, and possessed the quantitative analysis ability on account of the formation of a 1 : 1 metal–ligand complex. Furthermore, the density functional theory calculations were utilized to study the molecular orbitals as well as the spatial structure. Simultaneously, the cell experiments and zebra fish experiments verified the application value of the sensor in the biological field.

A novel selective and sensitive fluorescent sensor for detecting Fe³⁺ was designed and synthesized; it revealed obvious fluorescence quenching effect upon addition of Fe³⁺, and possessed the quantitative analysis ability on account of the formation of a 1 : 1 metal–ligand complex.

A “turn-on” small molecule fluorescent sensor for the determination of Al3+ ion in real samples: theoretical calculations, and photophysical and electrochemical properties

The fluorescence sensing properties of a naphthalene-based acetohydrazide (3) were investigated. A highly selective “turn-on” response was obtained towards Al3+ ions, and this was used for real sample analysis and development of paper test strips.