A highly selective fluorescent turn-on probe for Al3+ via Al3+-promoted hydrolysis of ester

Theoretical investigation on the ESIPT mechanism and fluorescent sensing mechanism of 2-(2'-hydroxyphenyl) thiazole-4-carboxaldeyde in methanol

2-(2'-Hydroxyphenyl) thiazole-4-carboxaldeyde (aldehyde 1) and hemiacetal 2 were selected to study the mechanism of excited-state intramolecular proton transfer and the detecting of Al³⁺ ion in methanol by using density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. Our theoretical results are in good agreement with the experimental values. The intramolecular H-bond is enhanced in the first excited-state based on the analyses of structural parameters, frontier molecular orbitals and electronic spectra. The stronger intramolecular H-bond is more favorable for ESIPT process. In order to further demonstrate the proton transfer process, we constructed the potential energy curves of probe 1 and 2 in both ground- and excited-states, and concluded that proton transfer processes in probe 1 and 2 are apt to happen in the S₁ state. In addition, the Mayer bond order, energy gap and absorption and fluorescence spectra were applied to interpret the process of detection of Al³⁺ ion.

A Naphthalimide-Based Fluorescence "Off-on-Off" Chemosensor for Relay Detection of Al3+ and ClO. Front Chem 2019;7:549. [PMID: 31428604 PMCID: PMC6687763 DOI: 10.3389/fchem.2019.00549]

A novel Al³⁺ chemosensor NPA was designed and synthesized on basis of the mechanism of ICT and CHEF. Upon addition of Al³⁺, the probe NPA displayed a bright green fluorescence under UV radiation and visual color change from yellow to colorless. Spectrum titrations showed that NPA could be recognized as a fluorescent turn-on probe with 10^-8 M detection level. The probe was successfully applied in real water sample and test paper. More important, NPA-Al³⁺ complex were used as a fluorescent turn-off probe for the detection of ClO^- with the detection as low as 2.34 × 10^-8 M. The performance of NPA to Al³⁺ and NPA-Al³⁺ complex to ClO^- demonstrated that NPA could be served as a sensitive probe and exhibit INHIBIT logic gate behavior with Al³⁺ and ClO^- as inputs.

A Schiff-base receptor based chromone derivate: Highly selective fluorescent and colorimetric probe for Al(III)

Upon excitation of the visible light, probes show colorimetric and fluorescent responses to the specific metal ion, which can be easily detected by the naked eye. Owing to the excitation of the visible light at 423 nm, a novel and simple Schiff-base receptor based chromone derivative called 7-methoxychromone-3-carbaldehyde-(indole-3-formyl) hydrazone (MCIH2) had been investigated as a selective and sensitive probe for Al³⁺ with colorimetric and fluorescent responses. Upon addition of Al³⁺ to compound MCIH2 solution, compound MCIH2 could respond to Al³⁺ with a good selective colorimetric signal, which was easily observed from colorless to yellow-green by the naked eye. Furthermore, a remarkable fluorescence emission enhancement with an "OFF-ON" signal by over 700-fold was triggered, but other various metal ions had no such significant effects on the fluorescence emission. In addition, the detection limit of compound MCIH2 for recognizing Al³⁺ was evaluated to be as low as 1 × 10^-7 M level, which was sufficiently low for sensing Al³⁺ widely distributed in various environmental and biological systems.

Facile synthesis of a water-soluble fluorescence sensor for Al3+ in aqueous solution and on paper substrate

In this study, a facile water-soluble fluorescence sensor 2-((2-hydroxybenzylidene)-amino)-2-(hydroxymethyl)propane-1,3-diol (ST) was synthesized via one-step reaction, and its fluorescence sensing performance for Al³⁺ both in aqueous solution and on paper substrate was evaluated. The results showed that ST exhibited an specific fluorescence "turn-on" response to Al³⁺ over other cations in aqueous solution as well as on the test paper. The limit of detection was found to be 3.2×10^-7M, which revealed that the obtained Schiff-base based fluorescence chemosensor ST possessed a great potential for the rapid, quantitative and qualitative detection of Al³⁺.

A Novel Fluorimetric Bulk Optode Membrane Based on NOS Tridentate Schiff Base for Selective Optical Sensing of Al3+ Ions

A novel fluorimetric optode has been developed for the highly selective and sensitive for the determination of ultra trace amounts of Al³⁺ ions. The proposed fluorescent optode is based on the incorporation of a simple and effective fluorescent sensor tridentate NOS Schiff base N-(2-hydroxynaphthylidene)-2-aminothiophenol (H₂L) in a plasticized PVC containing KTpClPB as a lipophilic anionic additive. H₂L was synthesized by a facile one-step Schiff base reaction. The plasticized PVC-membrane displays a calibration response for Al³⁺ ions over a wide concentration range from 1.0 × 10^-9 to 4.4 × 10^-3 mol/L. The fluorescence signal of the optode membrane can be easily recovered by immersion in 0.01 M EDTA. In addition to high stability and reproducibility, the sensor shows a unique selectivity towards Al³⁺ ion with respect to common co-existing cations, particularly Ga³⁺and In³⁺. The proposed optode was applied successfully for determination of Al³⁺ in some real samples, including bottled drinking waters, bottled mineral waters and soft drinks.

Thiasporines A-C, thiazine and thiazole derivatives from a marine-derived Actinomycetospora chlora

Thiasporine A (1), the first natural product with a 5-hydroxy-4H-1,3-thiazin-4-one moiety, along with two new thiazole derivatives, thiasporines B and C (2 and 3), were isolated from the marine-derived Actinomycetospora chlora SNC-032. The structures of 1-3 were established on the basis of comprehensive spectroscopic analysis and chemical methods. Thiasporine A showed cytotoxicity against the non-small-cell lung cancer cell line H2122 with an IC50 value of 5.4 μM.

A remarkable effect of N,N-diethylamino functionality on the optoelectronic properties of a salicylimine-based probe for Al(3+)

A new live-cell permeable, fluorescent probe comprised of a simple salicylimine-based Schiff base (SA1) has been developed for Al3+ with nano-molar sensitivity in aqueous media. SA1 was synthesized through a simple structural modification of a recently reported receptor SA2 by the incorporation of the N,Ndiethylamino (DEA) group as a fine controllable unit. This modification affects the performance of SA1 remarkably in terms of its sensitivity, water compatibility and efficiency as well as its mechanistic aspect. The presence of the DEA group in SA1 led to its dual channel emission due to the TICT state and at the same time its hydrophobic nature was also responsible for controlling the strong hydration of Al3+ ions in aqueous media which ultimately led to the high sensitivity of SA1 for Al3+. The structure of SA1 was confirmed by single crystal X-ray diffraction and its binding with Al3+ was studied in detail using UVvisible, fluorescence and 1H NMR spectral studies along with mass determination. The effort of getting a single crystal of Al3+–SA1 led to single crystals of Cl−/NO3 − complexes of protonated SA1 which were fully characterized by their XRD studies.