Execution of julolidine based derivative as bifunctional chemosensor for Zn2+ and Cu2+ ions: Applications in bio-imaging and molecular logic gate

A highly selective coumarin-based chemosensor for dual sensing of Cu2+ and Zn2+ ions with logic gate integration and live cell imaging

In this paper, a coumarin-based Schiff base chemosensor has been synthesized and developed to detect Cu2+ and Zn2+ ions in nanomolar concentrations. The probe selectively distinguishes Cu2+ and Zn2+ from among several metal ions in DMF : H2O (7 : 3, v/v, pH 7.4) HEPES buffer. The structure of the probe and its sensing behavior were investigated by FT-IR, UV-vis, fluorescence, HRMS, and NMR analyses, along with X-ray crystallography and computational studies. CIH detects Zn2+ and Cu2+ using different strategies: CHEF-induced fluorescence enhancement and paramagnetic fluorescence quenching, respectively. Job's plots show a 1 : 1 binding interaction between CIH and Cu2+ or Zn2+ ions. The binding constant values for Cu2+ (1.237 × 105 M-1) and Zn2+ (1.24 × 104 M-1) suggest a better ability for Cu2+ to interact with CIH than Zn2+. An extremely high sensitivity of the probe was highlighted by its very low detection limits (LOD) of 5.36 nM for Cu2+ and 3.49 nM for Zn2+. The regeneration of the probe with the addition of EDTA in its complexes allows the formation of molecular logic gates. CIH has been successfully employed in mitotracking and intracellular detection of Zn2+ and Cu2+ in SiHa cells.

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.

Dual-Mode Multiple Ion Sensing via Analyte-Specific Modulation of Keto-Enol Tautomerization of an ESIPT Active Pyrene Derivative: Experimental Findings and Computational Rationalization

A pyrene-based e xcited - state intramolecular proton transfer (ESIPT) active probe PMHMP was synthesized, characterized, and employed for the ppb-level, dual-mode, and high-fidelity detection of Cu²⁺ (LOD: 7.8 ppb) and Zn²⁺ ions (LOD: 4.2 ppb) in acetonitrile medium. The colorless solution of PMHMP turned yellow upon the addition of Cu²⁺, suggesting its ratiometric, naked-eye sensing. On the contrary, Zn²⁺ ions displayed concentration-dependent fluorescence rise till a 0.5 mole fraction and subsequent quenching. Mechanistic investigations indicated the formation of a 1:2 exciplex (Zn²⁺:PMHMP) at a lower concentration of Zn²⁺, which eventually turned into a more stable 1:1 (Zn²⁺:PMHMP) complex with an additional amount of Zn²⁺ ions. However, in both cases, it was observed that the hydroxyl group and the nitrogen atom of the azomethine unit were involved in the metal ion coordination, which eventually altered the ESIPT emission. Furthermore, a green-fluorescent 2:1 PMHMP-Zn²⁺ complex was developed and additionally employed for the fluorimetric analysis of both Cu²⁺ and H₂PO₄ ^- ions. The Cu²⁺ ion, owing to its higher binding affinity for PMHMP, could replace the Zn²⁺ ion from the preformed complex. On the other hand, H₂PO₄ ^- formed a tertiary adduct with the Zn²⁺-complex, leading to a distinguishable optical signal. Furthermore, extensive and organized density functional theory calculations were performed to explore the ESIPT behavior of PMHMP and the geometrical and electronic properties of the metal complexes.

Fluorimetric Recognition of Nerve Agent Mimic Diethylchlorophosphate Along with Cu2+/Hg2+ Ions Using Imidazole Possessing Sensor

An imidazole possessing sensor (1) has been designed and developed by simple one step reaction and characterization was done by using common spectroscopic methods. The fluorimetric sensing of nerve agent mimic, DCP, was carried out by observing blue shift in spectra accompanied with quenching in semi-aqueous solvent. The sensor was found proficient for the detection of DCP amongst other phosphates with detection limit of 69 nM. Furthermore, upon incorporation of various metal ions to CH₃CN:H₂O (4:1, v/v) solution of 1 (λ_ex 340 nm), the fluorescent probe turned non-fluorescent only in presence of Cu²⁺/Hg²⁺ ions. This was accompanied by fluorescent color change from light blue to yellow in case of Hg²⁺ and colorless in case of Cu²⁺ ions. Moreover, practical applications of sensor 1 were investigated for recognition of Cu²⁺ and Hg²⁺ ions in real water samples along with the detection of DCP in soil samples from different areas. Differential emission changes observed with addition of Hg²⁺ ions and DCP led to observation of "NOR" and an "INHIBIT" molecular photonic logic operations at 446 and 385 nm, respectively.

Novel selective "on-off" fluorescence sensor based on julolidine hydrazone-Al3+ complex for Cu2+ ion: DFT study

A hydrazone (T1) was synthesized by reacting 8-hydroxyjulolidine-9-carboxaldehyde with 2-furoic hydrazide and then modified with Al³⁺ ion to form a novel hydrazone Al³⁺ complex (T1-Al³⁺) in an aqueous solution (8% propylene glycol in 10 mM HEPES pH 5.5). The T1-Al³⁺ complex was studied as a Cu²⁺ selective sensor due to its highly efficient capacibility of paramagnetic quenching. The results showed that the T1-Al³⁺ complexed sensor possesses remarkable sensitivity and selectivity for Cu²⁺ ion in 8% propylene glycol in 10 mM HEPES pH 5.5 as compared with other tested analytes. Notably, this sensor has a broad linear detection range of 10-110 µM for Cu²⁺ ion and a detection limit level of 0.62 µM, which is lower than the Cu²⁺ concentration threshold in drinking water designated by the United States Environmental Protection Agency (EPA). Additionally, it was detectable for the presence of Cu²⁺ ion in mineral water and tap water samples. The selectivity of T1-Al³⁺ complexed sensor with Cu²⁺ ion could be explained by the basis of computation with Gaussian software complied with the basis sets of B3LYP/6-31 G(d,p)/LANL2DZ. Furthermore, only T1 exhibited anticancer efficacy against HeLa and U251 cells with MTT assay.

The Povarov Reaction: A Versatile Method to Synthesize Tetrahydroquinolines, Quinolines and Julolidines

The multicomponent Povarov reaction represents a powerful approach for the construction of substances containing N-heterocyclic frameworks. By using the Povarov reaction, in addition to accessing tetrahydroquinolines, quinolines and julolidines in a single step, it is possible to form the following new bonds: two Csp 3–Csp 3 and one Csp 3–Nsp 3, two Csp 2–Csp 2 and one Csp 2–Nsp 2, and four Csp 3–Csp 3 and two Csp 3–Nsp 1, respectively. This short review discusses the main features of the Povarov reaction, including its mechanism, the reaction scope by employing different catalysts and substrates, as well as stereoselective versions.

1 Introduction

2 Mechanism of the Povarov Reaction

3 Tetrahydroquinolines

4 Quinolines

5 Julolidines

6 Concluding Remarks

Irreversible coumarin based fluorescent probe for selective detection of Cu2+ in living cells

Copper ion (Cu²⁺) is an essential part of the living organisms. Cu²⁺ ions play a vital role in many biotic processes. An abnormal amount of Cu²⁺ ions may result in serious diseases. Herein, a novel "fluorescent ON" probe NC-Cu to trace minute levels of Cu²⁺ ions in presence of various biological active species has been developed. Lysosomal cells targeting group (Morpholine) was added to the probe. The spectral properties of probe NC-Cu were recorded in HEPES buffer (0.01 M, pH = 7.4, comprising 50% CH₃CN, λ_ex = 430 nm, slit: 5 nm). The synthesized probe NC-Cu work based on copper promoted catalytic hydrolysis of hydrazone and shows remarkable fluorescence enhancement. The reaction of the probe with Cu²⁺ ions was completed within 20 min. An excellent linear relationship (R² = 0.9952) was found and the limit of detection (LOD, according to the 3σ/slope) for Cu²⁺ ions was calculated to be 5.8 µM. Furthermore, NC-Cu was effectively functional in the living cells (KYSE30 cells) to trace Cu²⁺ ions.

An IMPLICATION-logic-based fluorescent probe for sequential detection of Cu2+ and phosphates in living cells

In this manuscript, we developed an IMPLICATION logic fluorescent probe, HL, for the sequential detection of Cu2+ and phosphate anions in extracellular and intracellular environments.

Design and Structural Regulation of AIE photosensitizers for imaging-guided photodynamic anti-tumor application

In recent years, photodynamic therapy (PDT) has become one of the important therapeutic methods for treating cancer. Aggregation-induced emission (AIE) photosensitizers (PSs) overcome the aggregation-caused quenching (ACQ) effects of conventional...

A New Reversible Colorimetric Chemosensor Based on Julolidine Moiety for Detecting F. J Fluoresc 2021;31:1675-1682. [PMID: 34387807 DOI: 10.1007/s10895-021-02801-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

We synthesized an original reversible colorimetric chemosensor PDJ ((E)-9-((2-(6-chloropyridazin-3-yl)hydrazono)methyl)-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-8-ol) for the detection of F^-. PDJ displayed a selective colorimetric detection to F^- with a variation of color from colorless to yellow. Limit of detection of PDJ for F^- was calculated as 12.1 µM. The binding mode of PDJ and F^- turned out to be a 1:1 ratio using Job plot. Sensing process of F^- by PDJ was demonstrated by ¹H NMR titration and DFT calculation studies that suggested hydrogen bond interactions followed by deprotonation. Moreover, the practicality of PDJ was demonstrated via a reversible test with TFA (trifluoroacetic acid).

Developing a new chemosensor targeting zinc ion based on two types of quinoline platform

A chemosensor DQ (2-(2-(quinolin-2-yl)hydrazinyl)-N-(quinolin-8-yl)acetamide), based on two quinoline moieties, has been synthesized. DQ could detect zinc ion through fluorescence turn-on in aqueous media. Limit of detection was calculated as 0.07 μM, far lower than the standard of WHO for zinc ion. The practicality of DQ was demonstrated via the successful results of reusability with EDTA, easy detection on the test strip, and precise quantification in real water samples. Additionally, sensor DQ could be applied to bioimaging of zinc ion in zebrafish. Sensing process of zinc ion by DQ was studied through fluorescence and UV-Vis spectroscopy, ¹H NMR titration, and ESI-mass spectrometry.

A novel tetrapeptide fluorescence sensor for early diagnosis of prostate cancer based on imaging Zn2+ in healthy versus cancerous cells

Zinc as a biomarker can be used to diagnose the early stage prostate cancer, while ZIP1 protein, a zinc transporter is significantly down-regulated in prostate cancer cells. This behavior leads to the apparent alteration of the enrichment ability for zinc between early prostate cancer tissues and healthy tissues. This difference inspires us to develop a novel Zn²⁺ sensor that applies to the clinic diagnosis of early prostate cancer. We designed a tetrapeptide sensor H₂L (Dansyl-Gly-Pro-Trp-Gly-NH₂) according to the photo-induced electron transfer principle (PET), and it performed adequately in Zn²⁺ imaging of prostate cell lines. Based on the assessment of Zn²⁺ enrichment ability, there was distinctly lower Zn²⁺ concentrate in prostate cancer cell lines than healthy prostate epithelial cells. Furthermore, H₂L displayed high sensitivity with a detection limit as low as 49.5 nM, and high specificity for Zn²⁺ detection. Also the low toxicity and the superior cell permeability of H₂L made the imaging of Zn²⁺ ions detection safe and rapid. We expect that H₂L to be a powerful tool for early diagnosis of prostate cancer and a good indicator for the precise resection of cancer tissue during surgery.

A novel pyrazole bearing imidazole frame as ratiometric fluorescent chemosensor for Al3+/Fe3+ ions and its application in HeLa cell imaging

New pyrazole bearing imidazole derivative was successfully synthesized and thoroughly characterized by various spectroanalytical techniques. The sensor DIBI shows a highly selective and sensitive fluorescent response with the addition of Al³⁺/Fe³⁺ ions in acetonitrile-water mixture. The strong fluorescent molecule exhibits a notable ratiometric emissions at 462 nm and 470 nm for Al³⁺ and Fe³⁺ ions, respectively (λ_ex = 280 nm). Job's plot studies conclude that the coordination between DIBI with Al³⁺/Fe³⁺ was 1:1 binding stoichiometry. The limit of detection of DIBI with Al³⁺/Fe³⁺ was calculated as 2.12 × 10^-7 M and 1.73 × 10^-6 M, respectively. The TD-DFT calculations further supported the photonics performances of the free probe and its complexes. The reversibility and reusability of the sensor molecule are studied using EDTA. The probe was used to track Al³⁺/Fe³⁺ in cancer cells via fluorescence microscopy.

A novel dual-function probe for recognition of Zn2+ and Al3+ and its application in real samples

A dual-function probe NAHH based on naphthalene was synthesized and characterized. Based on the combination effects derived from the inhabitation of photo-induced electron transfer (PET) and CN isomerization, probe NAHH achieved in the recognition of Zn2+ and Al3+ both through obvious fluorescence enhancement and color changes detected by naked eye, respectively. Probe NAHH showed high sensitivity with the limit of detection as low as 3.02 × 10-7 M for Zn2+ and 7.55 × 10-8 M for Al3+, indicated the capability of probe NAHH in trace detection for Zn2+ and Al3+. The binding ratio of NAHH with Zn2+ and Al3+ were all 1:1 determined by Job plot, and the corresponding association constant was calculated as 8.48 × 104 M-1 and 4.45 × 105 M-1, respectively. The mechanism was further confirmed by FT-IR, 1H NMR titration and ESI-MS analysis. Furthermore, probe NAHH was successfully applied in logic gate construction and the detection of Zn2+ and Al3+ in Songhua River and test stripe. Fluorescence imaging experiments confirmed that NAHH could be used to monitor Zn2+ in plant root.

A coumarin-based turn-on chemosensor for selective detection of Zn(II) and application in live cell imaging

A 2-oxo-2H-chromene-3-carbohydrazide (CHB) was synthesized by the reaction of salicylaldehyde with diethyl malonate and hydrazine hydrate. The recognition behaviors of CHB to Zn²⁺ were investigated and the results showed that CHB exhibits well selectivity and sensitivity to Zn²⁺ with fast response in PBS (pH = 7.24, 60% DMF), the co-existed cations and anions could not interfere the recognition between CHB and Zn²⁺. Besides, the detection limit of CHB for Zn²⁺ was calculated to be 0.95 μM. Furthermore, DFT, EI-MS data and Job's plot were applied for determining the sensing mechanism of CHB with Zn²⁺ and the results showed that a type of 2:1 complex was formed between CHB and Zn²⁺ with the binding constant was 1.32 × 10⁴ M^-2. At last, probe CHB was successfully applied for the imaging of Zn²⁺ in living cells.

Thieno[3,2-c]pyran: an ESIPT based fluorescence “turn-on” molecular chemosensor with AIE properties for the selective recognition of Zn2+ ion

Thieno[3,2-c]pyran was synthesized as a fluorescent turn-on chemosensor for the selective recognition of Zn²⁺ ions with a low detection limit (0.67 μM), and it also exhibited AIE properties.