Thiophene aldehyde-diamino uracil Schiff base: A novel fluorescent probe for detection and quantification of cupric, silver and ferric ions

Theoretical and Experimental In-vitro Studies of Novel Thiophene Based Organotellurium(IV) Complexes

Schiff bases are one of the important classes of organic compounds containing imine or azomethine functional groups with potential biological applications in medicinal chemistry. Nowadays, these compounds have attracted the scientific community's attention due to their ability to act as ligands in the formation of stable metal complexes with significant biological activity. In this connection, we have designed and synthesized six novel thiophene-based organoltellurium (IV) complexes using a novel N-((5-methylthiophen-2-yl) methylene)-2-nitroaniline (5MTCONA) schiff base. These complexes underwent analytical investigation (TGA, Powder XRD, SEM, EDAX) as well as spectral analysis (FT-IR, NMR, Mass spectrometry, UV-Vis). The in-vitro pharmacological evaluation of these compounds has been carried out as antimicrobial and antioxidant agents. To further corroborate our findings, we have implemented computational analyses (Semi empirical PM3 method, Molecular Docking, and ADMET) of all the compounds with Spartan-14, Hex-8.0., Swiss ADME software. Precisely, our study integrates experimental and theoretical aspects, offering innovative insights in the field of pharmaceutical sciences.

Synthesis and biological evaluation of novel salicylidene uracils: Cytotoxic activity on human cancer cell lines and inhibitory action on enzymatic activity

A series of salicylidene uracil (1-18) derived from 5-aminouracil and substituted salicylaldehydes were analyzed for cytotoxic activity and enzyme inhibitory potency. Nine out of eighteen derivatives (6-8, 10, 12-15, 18) are novel molecules synthesized for the first time in this work, and other derivatives were previously synthesized by our group. The compounds were characterized by Proton nuclear magnetic resonance, carbon nuclear magnetic resonance, fourier transform infrared spectroscopy, and elemental analysis. All compounds were tested for their in vitro cytotoxicity against PC-3 (human prostate adenocarcinoma), A549 (human alveolar adenocarcinoma), and SHSY-5Y (human neuroblastoma) cancer cell lines and the nontumorigenic HEK293 (human embryonic kidney cells) cell line. The 3,5-di-tert-butylsalicylaldehyde derived compound (8) was toxic to PC-3 human prostate adenocarcinoma cells, showing a promising IC50 value at 7.05 ± 0.76 μM. The present study also aimed to evaluate the inhibitory effects of the compounds against several key enzymes, namely carbonic anhydrase I and II (CA I and CA II), acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and glutathione reductase (GR), which are implicated in various global disorders, such as Alzheimer's disease, epilepsy, cancer, malaria, diabetes, and glaucoma. The inhibitory profiles of the tested compounds were assessed by determining their Ki values, which ranged from 2.96 to 9.24 nM for AChE, 3.78 to 12.57 nM for BChE, 8.42 to 25.74 nM for CA I, 7.24 to 19.74 nM for CA II, and 0.541 to 1.124 μM for GR. Molecular docking studies were also performed for all compounds. Most derivatives exhibited much more effective inhibitory action compared with clinically used standards. Thus, our findings indicate that the salicylidene derivatives presented in this study are promising drug candidates that need further evaluation.

A Review on Organic Fluorimetric and Colorimetric Chemosensors for the Detection of Ag(I) Ions

Organic compounds display several electronic and structural features which enable their application in various fields, ranging from biological to non-biological. These compounds contain heteroatoms like sulfur, nitrogen and oxygen, which provide coordination sites to act as ligands in the field of coordination chemistry and are used as chemosensors to detect various metal ions. This review article covers different organic compounds including thiourea, Schiff base, pyridine, thiophene, coumarin, triazolyl pyrenes, imidazole, fluorescein, thiazole, tricarbocyanine, rhodanine, porphyrin, hydrazone, benzidine and other functional groups based chemosensors, that contain heteroatoms like sulfur, nitrogen and, oxygen for fluorimetric and colorimetric detection of Ag+ in different environmental, agricultural, and biological samples. Further, the sensing mechanism and performances of these chemosensors have been discussed, which could help the readers for the future design of highly efficient, selective, and sensitive chemosensors for the detection and determination of Ag+ ions.

A Trinuclear Zinc Coordination Cluster Exhibiting Fluorescence, Colorimetric Sensitivity, and Recycling of Silver Ion and Detection of Cupric Ion

The detection and reusage of transition-metal ions play a crucial role in human health and environmental protection. Recently, various analytical methods and substances have been successfully applied to probe or sense silver ions; however, rare representative examples have been presented regarding the simultaneous detection of silver and silver recycling with the elemental silver powder form. Herein, an unparalleled sensing mechanism for silver ions and recycling silver in its elemental form is exemplified by a fluorescent trinuclear zinc coordination cluster possessing the dual function of colorimetric sensing of silver and responding cupric ions. A Schiff-base-based trinuclear zinc coordination cluster, 1, with formula Zn₃(L₁)₂(CH₃COO)₂(H₂O)₂, has been successfully synthesized by the initial exploration of multidentate ligand H₂L₁-((E)-2,4-di-tert-butyl-6-((2-hydroxy-3-methoxybenzy-lidene)amino)phenol) with various metal ions under self-assembly reactions. Complex 1 is highly fluorescent in solution and as a solid, in addition to acting as a fluorescence sensor toward Ag^I in ethanol media. Compound 1 displays distinctive sensing of Ag^I through the fluorescence quenching effect at 576 nm and signal augment at 446 nm over 11 kinds of cations in the absence of interference. The proposed sensing mechanism is attributed to the ligands in 1 which interact with Ag^I; the ligands undergo oxidation cyclization reaction, leading to the formation of 2 with the formula Zn₃(L₂)₄(CH₃COO)₂·2CH₃CH₂OH·H₂O, and Ag^I reduction to elemental Ag powder. Compound 1 presents specific selectivity and sensitivity for Ag^I in ethanolic solution with a detection limit of 0.1722 μM. The orange color of 1 changes to colorless during the mixing of a small amount of Ag^I, revealing its potential practical application in naked-eye detection of Ag^I. Furthermore, 2 exhibits obvious fluorescence emission at 448 nm (λ_ex = 380 nm) and selectively responds to Cu^II over 11 kinds of metal ions with the fluorescence "turn-off" owing to the formation of 3 in ethanolic solution; it also has a detection limit of 0.0226 μM.

A Water-Soluble Fluorescent Probe for the Selective Sensing of Ag+ and its Application in Imaging of Living Cells and Nematodes

In this study, an imidazole-coumarin based fluorescent probe was developed for the selective and sensitive detection of Ag⁺ in aqueous solution. Using a combination of Job plot, NMR titrations, and DFT calculations, the binding properties between Ag⁺ and the probe were deeply investigated, and the results revealed a 1:1 binding stoichiometry between the probe and Ag⁺ with a binding constant of 1.02 × 10⁶ M^-1. The detection limit was found to be 150 nM, which satisfies the requirement for the quantitative detection of Ag⁺ in real water samples. Moreover, the new probe, Ic, was successfully applied to sense Ag⁺ in HeLa and HepG2 cells as well as in C. elegans, indicating that it could be a useful tool for the environmental monitoring of Ag⁺ pollution. These results demonstrated that Ic could serve as a high-efficiency and low-cost fluorescent probe for tracking Ag⁺ in an aquatic environment and biological organisms.

A dual-response sensor based on NBD for the highly selective determination of sulfide in living cells and zebrafish

A dual chemosensor, 1-NO₂, showing fluorogenic and colorimetric responses was developed for the detection of sulfide in vitro and in vivo.

A reversible fluorescent probe for monitoring Ag(I) ions

Silver-containing nanomaterials are of interest for their antibiotic properties, for a wide range of applications from medicine to consumer products. However, much remains to be learnt about the degradation of such materials and their effects on human health. While most analyses involve measurement of total silver levels, it is important also to be able to measure concentrations of active free Ag(I) ions. We report here the preparation of a coumarin-based probe, thiocoumarin silver sensor 1 (TcAg1), that responds reversibly to the addition of silver ions through the appearance of a new fluorescence emission peak at 565 nm. Importantly, this peak is not observed in the presence of Hg(II), a common interferent in Ag(I) sensing. To establish the utility of this sensor, we prepared silver-doped phosphate glasses with demonstrated bactericidal properties, and observed the Ag(I) release from these glasses in solutions of different ionic strength. TcAg1 is therefore a useful tool for the study of the environmental and medical effects of silver-containing materials.

A multi-functional chemosensor for highly selective ratiometric fluorescent detection of silver(I) ion and dual turn-on fluorescent and colorimetric detection of sulfide

A multi-functional chemosensor 1 as silver and sulfide detector was synthesized by the combination of octopamine and 4-dimethylaminocinnamaldehyde. Sensor 1 exhibited a ratiometric fluorescence emission for Ag+ from blue to sky. The binding mode of 1 and Ag+ turned out to be a 1 : 1 ratio as determined using Job plot and electrospray ionization (ESI) mass spectral analyses. The sensing mechanism of 1 with silver ion was unravelled by 1H NMR titrations and theoretical calculations. Sensor 1 also discerned sulfide by enhancing fluorescence intensity and changing colour from yellow to colourless in aqueous solution. The sensing properties of 1 toward S2- were investigated by using ESI-mass analysis, Job plot and 1H NMR titrations. Moreover, 1 could be used as a detector for sulfide in a wide pH range.

Highly selective and sensitive fluorogenic ferric probes based on aggregation-enhanced emission with -SiMe3 substituted polybenzene

In this study, thiophene was linked to polybenzene to generate novel fluorescent probes, namely 3,4-diphenyl-2,5-di(2-thienyl)phenyl-trimethylsilane (DPTB-TMS) with a -SiMe₃ substituent and 3,4-diphenyl-2,5-di(2-thienyl)phenyl (DPTB) without the -SiMe₃ substituent, respectively. Both of the two compounds exhibit aggregation-enhanced emission (AEE) properties in tetrahydrofuran/water mixtures due to restricted intramolecular rotation of the peripheral groups, which make the two compounds good candidates for the detection of Fe³⁺ ions in aqueous-based solutions. The fluorescence intensity of the two compounds decreases immediately and obviously upon addition of a trace amount of Fe³⁺, and decreases continuously as the amount of Fe³⁺ increases. The fluorescence was quenched to 92% of its initial intensity when the amount of Fe³⁺ ions reached 6μmol for DPTB-TMS and to 80% for DPTB in the systems, indicating that the compound with the -SiMe₃ group is a more effective probe. The detection limit was found to be 1.17μM (65ppb). The detection mechanism is proposed to be static quenching. DPTB-TMS is highly efficient for the detection of ferric ions even in the presence of other metal ions. In addition, the method is also successfully applied to the detection of ferric ions in water, blood serum, or solid films. This indicates that these polybenzene compounds can be applied as low-cost, high selectivity, and high efficiency Fe³⁺ probes in water or in clinical applications.

New approach for the quantification of metallic species in healthcare products based on optical switching of a Schiff base possessing ONO donor set

A new method is reported for the quantification of some metallic components of healthcare products utilizing a Schiff base chelator derived from 2-hydroxyacetophenone and ethanolamine. The Schiff base chelator recognizes some metallic species such as iron, copper and zinc (important components of some healthcare products), and cadmium (common contaminant in healthcare products) giving colorimetric/fluorimetric response. It coordinates with Fe²⁺/Fe³⁺ and Cu²⁺ ions via ONO donor set and switches the colour to bright red, green and orange, respectively. Similarly, it switches 'ON' a fluorometric response when coordinates with Zn²⁺ and Cd²⁺ ions. In the present approach, detailed studies on the colorimetric and fluorimetric response of ONO Schiff base is investigated in detail. The Job plot for the complexation of ONO switch with various metal ions suggested formation of 1:1 (metal-chelator) complex with Fe²⁺, Fe³⁺, and Cu²⁺ while 1:2 (metal-chelator) for Zn²⁺ and Cd²⁺ ions. The limit of detection, limit of quantification are 6.73, 18.0, 25.0, 0.65, 1.10μM and 27.0, 72.0, 100.0, 2.60 and 4.40μM for Fe²⁺, Fe³⁺, Cu²⁺, Zn²⁺ and Cd²⁺ ions, respectively. Under the optimized conditions, chelator was used for the quantification of important metals present in healthcare products via direct dissolution and furnace treatment during sample preparation. The results were found precise and accurate for both sample preparation techniques using the developed method.