A Highly Selective Chemosensor for Al(III) and Zn(II) and Its Coordination with Metal Ions

The fluorescent property of 3-[(2-hydroxy-1-naphthyl) methylideneamino]benzoic acid and its application as fluorescent chemosensor for Hg2+ and Al3+ ions

This manuscript studies the fluorescent property of 3-[(2-hydroxy-1-naphthyl)methylideneamino]benzoic acid (H₂L). Fluorescent spectra show that in different solvents, H₂L displays different fluorescent properties, which can be attributed to the interaction between the solvents and H₂L. Further study indicates that H₂L exhibits a highly selective and sensitive recognition for Hg²⁺ ions in dimethylsulfoxide (DMSO), Al³⁺ ions in methanol and N,N'-dimethylformamide/water (DMF/H₂O, 1/1, v/v). The bonding modes and bonding ratio of H₂L and metal ions in different solvents are explored by Job's plot, ¹H NMR titration, and electrospray ionization mass spectrometry (ESI-MS). The probable mechanisms were discussed.

Quinoline containing acetyl hydrazone: An easily accessible switch-on optical chemosensor for Zn2

A simple chemosensor, namely, N-((quinolin-8-yl)methylene)acetohydrazide (1) was synthesized and used as an off-on fluorescence sensor, which exhibits high selectivity toward Zn²⁺ in aqueous media. The probe has large Stokes shift of >200nm, and its detection limit for Zn²⁺ is 89.3nM. The binding process was confirmed through UV-vis absorption analysis, fluorescence measurements, mass spectroscopy study, ¹H NMR spectra and density functional theory calculation. The crystal structures of Zn²⁺, Ni²⁺, and Cu²⁺ complexes based on 1 were determined through X-ray crystallographic analysis. The fluorescent probe was then applied to monitor intracellular Zn²⁺ in HeLa cells.

Acylhydrazone as a novel “Off–On–Off” fluorescence probe for the sequential detection of Al3+and F−

An acylhydrazone,SPBH,acts as a sequential fluorescence “Off–On–Off” probe for Al³⁺/F⁻, and the phenomenon was detectable by the naked eye.

A simple hydrazone as a multianalyte (Cu2+, Al3+, Zn2+) sensor at different pH values and the resultant Al3+ complex as a sensor for F−

A new colorimetric and fluorescence molecular chemosensor based on triazole hydrazone can be used as a multi-probe for selective detection of Al³⁺, Zn²⁺, and Cu²⁺ by monitoring changes in the absorption and fluorescence spectral patterns. Results show that Al³⁺ and Zn²⁺ ions can induce remarkable fluorescence enhancement at pH 6.0 and pH 10.0, respectively, while the addition of Cu²⁺ ions leads to a significant UV-visible absorption enhancement in the visible range at pH 6.0. In addition, the resultant Al³⁺ complex could act as an ‘on–off’ fluorescence sensor for F⁻. The fluorescence sensor was also used to monitor intracellular Al³⁺, Zn²⁺, and F⁻ in Hela cells.

A fluorescent probe for Al³⁺ and Zn²⁺ was synthesised, and the resultant Al³⁺-complex was used for the detection of F⁻.

Synthesis of Furo[2,3-c]pyridazines via Tandem Transition-Metal Catalysis

A general and efficient catalytic approach to synthesis of the furo[2,3-c]pyridazine ring system is reported. Building on the easily accessible 2-bromo-3-aminopyridizinone skeleton, a tandem Sonogashira coupling-cycloisomerization provides ready access to functionalized furopyridazines. A wide functional group tolerance was observed in the tandem reaction, which proceeds in high yield in 1-3 h. The structure of the heterocyclic ring system was confirmed through single-crystal X-ray crystallography.

Brightening Quinolineimines by Al3+ and Subsequent Quenching by PPi/PA in Aqueous Medium: Synthesis, Crystal Structures, Binding Behavior, Theoretical and Cell Imaging Studies

Recent years have witnessed an upsurge of Al³⁺ selective optical sensors involving simple Schiff bases to other complex organic frameworks. However, more than ∼95% of such reports lack crystallographic evidence, and proposals of binding sites for Al³⁺ are based upon spectroscopic evidence only. We herein synthesized and fully characterized a quinolineimine derivative (CMO) and explored its potential toward efficient detection of Al³⁺ with crystallographic evidence. The ongoing nonradiative photoinduced electron transfer (PET) and excited state intramolecular proton transfer (ESIPT) processes in CMO got inhibited via the chelation enhanced fluorescence (CHEF) effects induced by Al³⁺, and consequently turn-on fluorescence response was observed with 18-fold emission enhancements. The theoretical calculations performed were in good consonance with experimental results. We also explored further the applicability of the CMO·Al³⁺ complex toward highly sensitive and selective detection of inorganic phosphate (PPi) and an explosive picric acid (PA) via fluorescence quenching processes through two different chemical routes. The bioimaging of Al³⁺ and PPi were carried out in the living human cancer cells (MCF-7).

A highly selective and sensitive turn-on fluorescent probe for the detection of Al3+ and its bioimaging

A novel fluorescent sensor, 1-((2-hydroxynaphthalen-1-yl)methylene)urea (ocn) has been designed and applied as a highly selective and sensitive fluorescent probe for recognition of Al³⁺ in Tris-HCl (pH = 7.20) solution. The probe ocn exhibits an excellent selectivity to Al³⁺ over other examined metal ions, anions and amino acids with a prominent fluorescence 'turn-on' at 438 nm. ocn binds to Al³⁺ with a 2:1 binding stoichiometry and the detection limit was 0.3 μM. Furthermore, its capability of biological application was evaluated and the results showed that the sensor could be used to detect Al³⁺ in living cells.

Both visual and fluorescent sensors for Zn(2+) based on bis(pyrrol-2-yl-methyleneamine) platform

Two bis(pyrrol-2-yl-methyleneamine) chemo-sensors, 1, 3- and 1, 4-bis[3,4-dimethyl-5-ethyloxy -carbonyl-pyrrol-2-yl-methyleneamine]benzene (H2L(1) and H2L(2), respectively) have been synthesized and characterized, which exhibit high selectivity as off-on fluorescence sensors toward Zn(2+) in CH3CN/H2O (9:1, v/v) solution. The detection limits of both sensors are at the parts per million level. Moreover, the probes H2L(1) and H2L(2) could sense Zn(2+) by "naked eye" with a color change from colorless to yellow, and from yellow to dark yellow, respectively. To test the practical use of the probes, the determination of Zn(2+) in real water samples was also evaluated.

Simultaneous bioimaging recognition of Al3+ and Cu2+ in living-cell, and further detection of F- and S2- by a simple fluorogenic benzimidazole-based chemosensor

A simple Schiff base (BMSA) prepared from salicylaldehyde and 2-(1H-benzo[d]imidazol-2-yl)aniline was evaluated as an efficient fluorescent chemosensor for the selective recognition of Al³⁺and Cu²⁺ over other common metal ions. This sensor could detect Al3⁺ in CH₃OH/PBS with distinct emission red-shift (the detection limit 0.31μM)and Cu²⁺in CH₃OH/Tris-HCL (the detection limit 0.54μM) with obvious fluorescence quenching. The obtained BMSA-Al³⁺ and BMSA-Cu²⁺ complexes could act as cascade sensors for detecting F^- and S^2-, respectively. The recognizing behavior of BMSA toward Al³⁺and Cu²⁺ has been investigated in detail through Job's Plot, FT-IR NMR, and HRMS analysis. Moreover, this chemosensor was verified to be of low cytotoxicity and good imaging characteristics for the detection of Al³⁺ and Cu²⁺, and further for the recognition of F^- and S^2- in living cells, suggesting that BMSA was proved to be a useful tool for tracking Al3⁺/Cu²⁺and F^-/S^2- ions in vivo.

Development of a cell permeable red-shifted CHEF-based chemosensor for Al(3+) ion by controlling PET

A structurally modified quinazoline derivative (L) acts as highly selective chemosensor for Al(3+) ions in DMSO-H2O (1:9, v/v) over the other competitive metal ions. L shows a red shifted fluorescence after the addition of Al(3+) ions and later the further fluorescence enhancement is due to chelation enhanced fluorescence (CHEF) through inhibition of photoinduced electron transfer (PET). This probe (L) detects Al(3+) ions as low as 9nM in DMSO-H2O (1:9, v/v) at biological pH. The non-cytotoxic probe (L) can efficiently detect the intercellular distribution of Al(3+) ions in living cells under a fluorescence microscope to exhibit its sensible applications in the biological systems.

Preparation, regulation and biological application of a Schiff base fluorescence probe

A facile fluorescence switch with Schiff base units was designed and achieved by nucleophilic addition and dehydration reaction. The fluorescence of the probe can be regulated by metal ions (Al(3+) and Cu(2+)). The whole process shows that the weak fluorescence of the probe enhances with the addition of Al(3+), and then the strong fluorescence of the probe/Al(3+) ensemble reduces by introducing Cu(2+). Meanwhile, the solution color changes of the probe with metal ions can be observed under 365 nm UV-vis light from weak light, pale green, green, pale green to weak light. Noticeably, the photo regulation processes of the probe by metal ions can be realized in the biological system and applied in cells imaging. The work provides a new strategy for designing facile regulation probe and develops a new application for Schiff base derivatives.

Deciphering the CHEF-PET-ESIPT liaison mechanism in a Zn2+ chemosensor and its applications in cell imaging study

Proper fusion of fluorescence mechanisms in a single fluorophore unit is highly desirable to obtain better sensitivity, as well as selectivity towards a particular metal ion.

Design-specific mechanistic regulation of the sensing phenomena of two Schiff bases towards Al3+

We report herein two optical probes (R1 and R2) for the fluorogenic detection of Al³⁺ at the level of 10⁻⁸ M.

A single chemosensor for bimetal Cu(ii) and Zn(ii) in aqueous medium

A new quinazoline-based bimetal chemosensor for Cu(ii) and Zn(ii) in aqueous medium was synthesized. It can act as a “turn-off” sensor for Cu(ii) with the excitation wavelength of 356 nm, and a “turn-on” sensor for Zn(ii) when excited at 416 nm.

A highly selective and sensitive fluorescent turn-on Al3+ chemosensor in aqueous media and living cells: experimental and theoretical studies

A highly selective and sensitive fluorescent chemosensor exhibited enhanced fluorescence in the presence of Al³⁺ and in living cells.

A facile Al(iii)-specific fluorescence probe and its application in biological systems

A facile fluorescent probe for Al(iii) was developed and applied in biological systems.

A highly selective fluorescent probe for Al(3+) based on quinoline derivative

A novel Schiff base fluorescent probe, 1-phenyl-3-methyl-5-hydroxypyrazole-4-carbaldehyde (2'-methylquinoline-4'-formyl) hydrazone (PMHCH), for selective detection of Al(3+) has been designed and synthesized. Upon addition of various metal ions, the receptor only shows 286-fold enhancement of fluorescence intensity which might be attributed to a 1:1 stoichiometry between PMHCH and Al(3+) and the photo-induced electron transfer progress in the present of Al(3+) at 505n m. More importantly, the detection limit of PMHCH for Al(3+) could reach at 10(-7) M level.

Two novel bipyrazole derivative ligands: Synthesis, crystal structure, theoretical studies, and sensitive response toward Fe(3.)

Two novel bipyrazole derivative ligands L1 (4-(di(1H-pyrazol-1-yl)methyl)-N,N-diphenylaniline) and L2 (4-(di(1H-pyrazol-1-yl)methyl)-N,N-bis(4-ethoxy phenyl)aniline), were synthesized, and fully characterized. The crystal structures of the two ligands were confirmed by single-crystal X-ray diffraction analysis. The structural analysis revealed that two pyrazole units are attached to the same carbon atom connected with triphenylamine moiety. The UV-vis absorption and fluorescence spectral properties of the ligands were investigated and explained relying on theoretical calculation. Significantly, it was found that the ligands display an exclusively selective and sensitive response toward Fe(3+) with aid of UV-vis absorption spectroscopic methods.

X-ray structurally characterized sensors for ratiometric detection of Zn2+ and Al3+ in human breast cancer cells (MCF7): development of a binary logic gate as a molecular switch

A very simple molecule derived from salicylaldehyde and N-phenyl ethylenediamine (L1) functions as a dual-mode ratiometric fluorescence “turn on” sensor for Zn²⁺ and Al³⁺ at two different wavelengths.

An easy and accessible water-soluble sensor for the distinctive fluorescence detection of Zn2+ and Al3+ ions

A water-soluble fluorescence sensor was facilely synthesized and it can be used for the distinctive fluorescence detection of Zn²⁺ and Al³⁺ ions.

Synthesis and characterization of a novel, ditopic, reversible and highly selective, “Turn-On” fluorescent chemosensor for Al3+ ion

A ditopic Schiff base fluorescent chemosensor, L (OFF state), selectively senses Al³⁺ by inhibition of ESIPT/GSIPT, CN isomerization and CHEF (ON state).

Detection of copper(ii) and aluminium(iii) by a new bis-benzimidazole Schiff base in aqueous media via distinct routes

Synthesis and characterization of a bis-benzimidazole appended Schiff base ligand, 2-(3,5-bis(1H-benzimidazole-2-yl)-phenyliminomethyl)phenol (H3L) displaying excellent selectivity towards Cu²⁺and Al³⁺in mixed aqueous media.