Design of a novel coumarin-based multifunctional fluorescent probe for Zn2+/Cu2+/S2− in aqueous solution

Synthesis of fluorescent dicyanomethylenevinyl-1,3-dicoumarin compounds with donor-acceptor-π-donor (D-A-π-D) system and investigation of their photophysical, NLO, and chemosensor properties: Part 1

Coumarin compounds have heterocyclic core with different properties such as high quantum yields, broad Stokes shifts, and superior photophysical and biological activity. It is known that fluorescence properties increase with increased intramolecular charge transfer in systems where electron-withdrawing or donor groups are attached to different positions of the coumarin compound. When these compounds interact with analytes in the environment, the analytes in the environment can be detected by quenching or increasing fluorescence. For this purpose, dicyanomethylenevinyl-1,3-dicoumarin compounds were obtained and 1H NMR, 13C NMR, FT-IR, HR-MS elucidated their structures. To determine the photophysical properties of the synthesized compounds, absorption, and emission spectra were examined in solvents with different polarities, and also quantum yields and Stokes shifts were calculated. Additionally, the sensitivity/selectivity properties of the compounds towards various anions were investigated by spectrophotometric, spectrofluorometric, and 1H NMR titration methods. The limit of detection (LOD) of the sensors to sense cyanide anion was considered based on absorption titration. The pKa value of compound that could be pH sensor candidate was determined. Thermogravimetric analysis was performed as an important parameter for compounds in electro-optical (EO) systems. Additionally, nonlinear optical (NLO) properties of the compounds were calculated experimentally and theoretically. The some experimental results were explained by Density Functional Theory (DFT) and time-dependent DFT (TDDFT) calculations.

Recent Development on Copper-Sensor and its Biological Applications: A Review

Metal ion recognition is one of the most prospective research topics in the field of chemical sensors due to its wide range of clinical, biological and environmental applications. In this context, hydrazones are well known compounds that exhibit metal sensing and several biological properties due to the presence of N=CH- bond. Some of the biological properties includes anti-cancer, anti-tumor, anti-oxidant, anti-microbial activities. Hydrazones are also used as a ligand to detect metal ion as well as to generate metal complexes that exhibit medicinal properties. Thus, in recent years, many attempts were made to develop novel ligands with enhanced metal sensing and medicinal properties. In this review, some of the recent development on the hydrazones and their copper complexes are covered from the last few years from 2015-2023. These includes significance of copper ions, synthesis, biological properties, mechanism and metal sensing properties of some of the copper complexes were discussed.

A novel diarylethene-based fluorescence sensor for Zn2+ detection and its application

A series of fluorometric sensors of Zn2+ have been synthesized due to the significant function of Zn2+ in the human body and environment. However, most of probes reported for detecting Zn2+ have high detection limit or low sensitivity. In this paper, an original Zn2+ sensor, namely 1o, was synthesized by diarylethene and 2-aminobenzamide. When Zn2+ was added, the fluorescence intensity of 1o increased by 11 times within 10 s, along with a fluorescence color change from dark to bright blue, and the detection limit (LOD) was calculated to be 0.329 μM. According to Job's plot curves, the binding mode of 1o and Zn2+ was measured as 1:1, which was further proved by 1H NMR spectra, HRMS and FT-IR spectra. The logic circuit was designed to take advantage of the fact that the fluorescence intensity of 1o can be controlled by Zn2+, EDTA, UV and Vis. In addition, Zn2+ in actual water samples were tested, in which the recovery rate of Zn2+ was between 96.5 % and 109 %. Furthermore, 1o was successfully made into a fluorescent test strip, which could be used to detect Zn2+ in the environment economically and conveniently.

Detection of S2− in Water by a Glucose Enhanced Water-Soluble Fluorescent Bioprobe

That sulfide anions (S2−) in aquatic environments are produced by microorganisms through degrading sulfur-containing proteins and other organics are harmful to human health. Thus, it is of significance to develop a convenient method for the detection of S2− in water. Small molecular fluorescent probes are very popular for their advantages of visualization, real-time, high sensitivity, and convenience. However, low solubility in water limits the application of existing S2− probes. In this work, we found that our previously developed water-soluble glycosylated fluorescent bioprobe Cu[GluC] can achieve detection of S2− in water. Cu[GluC] can restore fluorescence within 20 s when it encounters S2− and shows good sensitivity towards S2− with a detection limit of 49.6 nM. Besides, Cu[GluC] derived fluorescent test strips were obtained by immersion and realized conveniently visual S2− detection in water by coupling with a UV lamp and a smartphone app. This work provides a fluorescent bioprobe with good water solubility as well as its derived fluorescent test strip for sensitive and simple detection of S2− in water, which shows good prospects in on-site water quality monitoring.

Hydrazone derivative bearing coumarin for the relay detection of Cu2+ and H2S in an almost neat aqueous solution and bioimaging in lysosomes

A new morpholine functionalized coumarin-based fluorescent probe 1 was easily synthesized. The probe realized the sequentially detecting of Cu²⁺ and H₂S in the HEPES buffer solution (20 mM, pH = 5.0). It made a turn-off fluorescence response to Cu²⁺ by using a complex formation with a 2:1 binding mode, and the resulting complex was able to detect H₂S according to the displacement approach with a turn-on fluorescence response. The detecting limits of probe 1 for Cu²⁺ and 1-Cu²⁺ system for H₂S were calculated to be 26 nM and 88.5 nM, respectively. This "on-off-on" recognition process was demonstrated by ultraviolet-visible spectroscopy, fluorescence spectroscopy, using proton nuclear magnetic resonance studies, electrospray ionization mass spectroscopy, single crystal X-ray diffraction, and using density functional theory calculations. In addition, both cell imaging and co-staining experiments showed that the probe could be utilized to visually detect Cu²⁺ and H₂S in lysosomes.

A coumarin-based reversible fluorescent probe for Cu2+ and S2− and its applicability in vivo and for organism imaging

A highly selective fluorescent probe was designed to detect Cu²⁺ and S²⁻ in HeLa cells, zebrafish, and soybean root tissue.

A dual-function probe based on naphthalene for fluorescent turn-on recognition of Cu2+ and colorimetric detection of Fe3+ in neat H2O

A simple naphthalene derivative, 6-hydroxy-2-naphthohydrazide (NAH), was designed and synthesized through two facile steps reactions with the 6-hydroxy-2-naphthoic acid (NCA) as the starting material. In neat H₂O (10% 0.01 M HEPES buffer, v/v, pH = 7.4), probe NAH showed a highly selective and sensitive response towards Fe³⁺ via perceptible color change and displayed "turn-on" dual-emission fluorescence response for Cu²⁺. The binding stoichiometry ratio of NAH/Cu²⁺ and NAH/Fe³⁺ were all confirmed as 1:1 by the method of fluorescence job's plot and UV-Vis job's plot, respectively. Probe NAH can be used over a wide pH range for the determination of Fe³⁺ (2.0-10.0) and Cu²⁺ (6.0-10.0) without interference from other co-existing metal ions. A possible detection mechanism was the hydrolysis of NAH upon the addition of Fe³⁺ or Cu²⁺, thereby leading to the formation of 6-hydroxy-naphthalene-2-carboxylic acid (NCA) which was further confirmed by the various spectroscopic techniques including FT-IR, ¹H NMR titration and HRMS. Moreover, NAH was successfully applied to the detection of Cu²⁺ and Fe³⁺ in tap water, ultrapure water and BSA.

Formation of multilayer through layer-by-layer assembly of starch-based polyanion with divalent metal ion

The layer-by-layer (LbL) assembly between metal ion and starch-based anion driven by electrostatic interaction was investigated. Multilayer films were obtained from starch-based derivative containing carboxyl groups (SC) with copper or lead ions. It was found that the concentration of metal ion in aqueous solution decreased with increasing the layers. X-ray photoelectron spectroscopy exhibited the content of Cu(II) was higher when the surface was copper-ion-layer than that composed of SC. The surface of the film was smooth and no obvious fault plane was observed on its cross-section, which also indicated that the LbL assembly between starch-based polyanion and metal ion was carried out. Sodium alginate was adopted as another polyanion to conduct the LbL assembly. Part of metal ion was replaced with rhodamine B to fabricate composite multilayer. During such an assembly, the concentration of copper ion in aqueous solution decreased with increasing the layers as well. These phenomena suggested that the LbL assembly between polysaccharide-based polyanion and metal ion was feasible.

A relay identification fluorescence probe for Fe3+ and phosphate anion and its applications

A simple relay identification fluorescence probe for Fe³⁺ and phosphate anion with "on-off-on" switching was designed and synthesized based on the phenylthiazole and biphenylcarbonitrile. Probe 1 displayed highly selective and sensitive recognition to Fe³⁺ in HEPES aqueous buffer (EtOH/H₂O=2:8, v/v, pH=7.4) solutions. The optimized structures and HOMO and LUMO of probe 1 and [1-Fe³⁺] complex were obtained by the density functional theory (DFT) calculations with B3LYP as the exchange and correlation functional using a suite of Gaussian 09 programs. The [1-Fe³⁺] complex solution also showed a high selectivity toward PO₄^3-. The lower limits of detection of probe 1 to Fe³⁺ and [1-Fe³⁺] complex to PO₄^3- were estimated to 1.09×10^-7M and 1.86×10^-7M. Besides, the probe 1 also was used to detected the target ions in real water sample and living cells successfully.

A novel Schiff base derivative of pyridoxal for the optical sensing of Zn2+ and cysteine

An easy to prepare novel vitamin B₆ cofactor derivative 3-hydroxy-N′-((3 hydroxy-5-(hydroxymethyl)-2-methylpyridin-4-yl)methylene)-2-naphthohydrazide (NPY) was applied for the optical detection of Zn²⁺ and cysteine in the aqueous DMSO medium.

Development of a coumarin-furan conjugate as Zn2+ ratiometric fluorescent probe in ethanol-water system

In this study, a novel coumarin-derived compound bearing the furan moiety called 7-diethylamino-3-formylcoumarin (2'-furan formyl) hydrazone (1) has been designed, synthesized and evaluated as a Zn²⁺ ratiometric fluorescent probe in ethanol-water system. This probe 1 showed good selectivity and high sensitivity towards Zn²⁺ over other metal ions investigated, and a decrease in fluorescence emission intensity at 511nm accompanied by an enhancement in fluorescence emission intensity at 520nm of this probe 1 was observed in the presence of Zn²⁺ in ethanol-water (V : V=9 : 1) solution, which provided ratiometric fluorescence detection of Zn²⁺. Additionally, the ratiometric fluorescence response of 1 to Zn²⁺ was nearly completed within 0.5min, which suggested that this probe 1 could be utilized for sensing and monitoring Zn²⁺ in environmental and biological systems for real-time detection.

An anthraquinone-based highly selective colorimetric and fluorometric sensor for sequential detection of Cu2+ and S2− with intracellular application

An anthraquinone-based highly selective colorimetric and fluorometric probe for sequential detection of Cu²⁺ and S²⁻ with intracellular application is reported.

A highly selective colorimetric chemosensor for cyanide and sulfide in aqueous solution: experimental and theoretical studies

A selective chemosensor was developed for the colorimetric detection of CN⁻ and S²⁻ in aqueous solution.

A “turn-on” fluorescent probe for the detection of Cu2+ in living cells based on a signaling mechanism of NN isomerization

A “turn-on” probe A based on coumarin with a mechanism of NN isomerization was developed for detecting Cu²⁺ in living cells.