Highly sensitive and selective “naked eye” sensing of Cu(II) by a novel acridine-based sensor both in aqueous solution and on the test kit

Recent Advances in the Synthesis and Optical Applications of Acridine-based Hybrid Fluorescent Dyes

Acridine-based hybrid fluorescent dyes represent a category of dyes that integrate the acridine chromophore with other functional groups or materials to enhance their fluorescence properties. These dyes have garnered substantial attention across various domains, encompassing bioimaging, sensing, and optoelectronics. In recent years, researchers have directed their efforts toward fabricating acridine-based hybrid fluorescent dyes with improved water solubility, biocompatibility, and targeting capabilities. These advancements have facilitated their utilization in biological imaging applications, such as monitoring cellular processes, investigating protein-protein interactions, and detecting specific biomolecules. This review delineates the recent progress in synthesizing acridine-based hybrid fluorescent dyes and their applications in optical properties over the past decade. This review is anticipated to catalyze the development of innovative fluorescent materials featuring heightened properties and functionalities.

Experiments and Calculation on New N,N-bis-Tetrahydroacridines

Tetrahydroacridines arouse particular interest due to the potential possibilities of application in the medical field and protection against corrosion. Bis-tetrahydroacridines were newly synthesized by Pfitzinger condensation of 5,5'-(ethane-1,2-diyl) diindoline-2,3-dione with several cyclanones. NMR, MS, and FT-IR were used to prove their molecular structure. In addition, a computer-aided study was performed for the lowest energy conformers of each structure, in vacuum conditions, at ground state using DFT models to assess their electronic properties. UV-Vis and voltammetric methods (cyclic voltammetry, differential pulse voltammetry, and rotating disk electrode voltammetry) were used to investigate their optical and electrochemical properties. The results obtained for these π-conjugated heteroaromatic compounds lead to the conclusion that they have real potential in applications in different fields such as pharmaceuticals and especially as corrosion inhibitors.

Architecture of Easy-to-Synthesize and Superior Probe Based on Aminoquinoline Appended Naphthoquinone: Instant and On-Site Cu2+ Ion Quantification in Real Samples and Unusual Crystal Structure and Logic Gate Operations

Easy-to-synthesize aminoquinoline (AQ) appended naphthoquinone (NQ)-based colorimetric and ratiometric probe (AQNQ) was successfully synthesized in one step with high yield and low cost, and was utilized to supply an effective solution to critical shortcomings encountered in Cu2+ analysis. The structure of AQNQ and its interaction with Cu2+ forming an unusual AQNQ-Cu complex were enlightened with single-crystal X-ray diffraction analysis and different spectroscopic methods. AQNQ-Cu complex is the first Cu2+ containing dinuclear crystal where the octahedral coordination sphere is fulfilled through the coordination of a NQ oxygen atom. AQNQ exhibited long-term stability (more than 1 month), superior probe ability toward Cu2+ with quite fast response (30 s), high selectivity among many ions, and limit of detection of 12.13 ppb that is significantly below the highest amount of Cu2+ allowed in drinking water established by both WHO and EPA. Ratiometric determination of Cu2+ using AQNQ was performed with high recovery and low RSD values for drinking water, tap water, lake water, cherry, and watermelon samples. Colorimetric on-site determination including smartphone and paper strip applications, IMPLICATION, and INHIBIT logic gate applications were successfully carried out. The reversibility and reusability of the response to Cu2+ ions with the paper strip application were examined for the first time.

Synthesis and investigation on optical and electrochemical properties of 2,4-diaryl-9-chloro-5,6,7,8-tetrahydroacridines

A facile synthesis of 2,4-diaryl-9-chloro-5,6,7,8-tetrahydroacridine derivatives is reported which is based on POCl₃-mediated cyclodehydration followed by double Suzuki-Miyaura cross-coupling. The absorption and fluorescence properties of the obtained products were investigated and their HOMO/LUMO energy levels were estimated by cyclic voltammetry measurements. Besides, density functional theory calculations were carried out for further exploration of their electronic properties.

Simple and sensitive colorimetric sensors for the selective detection of Cu(ii)

A simple, sensitive colorimetric probe for detecting Cu(ii) ions with fast response has been established with a detection limit of 2.82 μM. UV-Vis spectroscopy along with metal ion response, selectivity, stoichiometry, competition was investigated. In the presence of copper(ii), the UV-Vis spectrum data showed significant changes and the colorimetric detection showed a color change from colorless to yellow. After the selective binding of receptor L with Cu(ii), the UV-visible absorption at 355 nm decreased dramatically, a new absorbance band appeared at 398 nm and its intensity enhanced with the increase in the amount of Cu(ii). Moreover, it exhibited highly selective and sensitive recognition towards Cu(ii) ions in the presence of other cations over the pH range of 7-11. The complex structure was verified by FT-IR spectroscopy, elemental analysis and quantum mechanical calculations using B3LYP/6-31G(d) to illustrate the complex formation between L and Cu(ii). According to the Job plot and the quantum mechanical calculations, the stoichiometric ratio for the complex formation was proposed to be 1 : 1.

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.

Fused 1,5-Naphthyridines: Synthetic Tools and Applications

Heterocyclic nitrogen compounds, including fused 1,5-naphthyridines, have versatile applications in the fields of synthetic organic chemistry and play an important role in the field of medicinal chemistry, as many of them have a wide range of biological activities. In this review, a wide range of synthetic protocols for the construction of this scaffold are presented. For example, Friedländer, Skraup, Semmlere-Wolff, and hetero-Diels-Alder, among others, are well known classical synthetic protocols used for the construction of the main 1,5-naphthyridine scaffold. These syntheses are classified according to the nature of the cycle fused to the 1,5-naphthyridine ring: carbocycles, nitrogen heterocycles, oxygen heterocycles, and sulphur heterocycles. In addition, taking into account the aforementioned versatility of these heterocycles, their reactivity is presented as well as their use as a ligand for metal complexes formation. Finally, those fused 1,5-naphthyridines that present biological activity and optical applications, among others, are indicated.