A new fluorescent chemosensor for Al(3+) ion based on schiff base naphthalene derivatives

A Novel Naphthylidene-diimine Chemosensor for Selective Colorimetric and Fluorometric Detection of Al3+ and CN- Ions

A naphthylidene-diimine L2 was newly designed, and its structure was identified by elemental analysis and spectroscopic methods. The effect of temperature, acid-base and light on enol-keto tautomerism in this Schiff base was evaluated by colorimetry, UV-Vis and fluorescence spectroscopy. Under irradiation 365 nm, L2 emitted yellow, orange and strong green emission in pure, basic and aqueous DMSO media (v/v, 1/1), respectively. Its ionochromic behavior against various cations (Fe3+, Al3+, Cr3+, Cu2+, Co2+, Ni2+, Zn2+, Cd2+, Pb2+, Ba2+ and Ag+) and anions (F-, Cl-, CH3COO-, SO32-, S2O32-, HSO4-, H2PO4-, NO3-, CN-, and OH-) was investigated in aqueous DMSO media (v/v, 1/1) by UV-Vis and fluorescence experiments. Dark yellow color of L2 changed to colorless for Fe3+, Cr3+ and HSO4- ions, and turned to light yellow for Al3+ and Cu2+ ions, and to orange for CN- and OH- ions. According to UV-Vis data, the chemosensor displayed selective recognition towards Fe3+, Al3+, Cu2+, HSO4-, CN- and OH- with a 1:1 stoichiometric ratio. At the excitation wavelength of 365 nm, L2 gave strong yellowish white emission (λem = 445 and 539 nm) in the presence of Al3+, and the intensity increased about 12.5 times. On the other hand, the chemosensor displayed one emission band at 452 nm and 450 nm in the presence of CN- and OH- with 1.9 fold and 2.3 fold fluorescence enhancement, respectively.

A new highly selective "off-on" typical chemosensor of Al3+, 1-((Z)-((E)-(3,5-dichloro-2-hydroxybenzylidene)hydrazono)methyl) naphthalene-2-ol, an experimental and in silico study

A new promising fluorescent chemosensor based on a 2-hydroxynaphthaldehyde skeleton was successfully synthesized through double imine formation as a yellow solid with an overall chemical yield of 63%. The compound showed UV/Visible maxima of at 394 nm in DMSO. Based on spectroscopic data of FTIR, ToF-HRMS, 1H-NMR, and 13C-NMR, the product was characterized as 1-((Z)-((E)-(3,5-dichloro-2-hydroxybenzilydine)hydrazono)methyl)naphthalene-2-ol. Upon experimental study, the compound was confirmed as a highly selective and reversible off-on typical chemosensor against Al3+ with an emission quantum yield of 0.203 ± 0.009. The Job's plot analysis revealed that a highly stable 1:1 complex was formed with an association constant of 8.73 × 105 M-1. A pH-dependent study showed that the sensor was potentially applicable at physiological conditions (pH 7-8) in a mixture of DMSO : H2O (99 : 1, v/v). The LoD and LoQ of the chemosensor towards Al3+ in DMSO were found to be 0.04 and 0.14 μM respectively. Based on DFT and TD-DFT calculation (B3LYP hybrid method/basis set of 6-311+G(d,p)), the sensing mechanism of the chemosensor to the ion was discovered as inhibition of excited-state intramolecular proton transfer (ESIPT).

A bifunctional fluorescent probe for sensing of Al3+ and H2S

Al3+ and H2S play essential roles in various physiological processes. However, excess Al3+ and H2S are harmful to health. Therefore, it is necessary to design a sensitive method for the detection of Al3+ and H2S. In this work, compound L was developed based on salicylaldoxime and 4-aminobenzamide. L displayed aggregation-induced emission (AIE) characteristics in the solid state due to a unique dimer formation via intermolecular hydrogen bonds. In addition, L could serve as a multi-responsive fluorescence probe for Al3+ based on the coordination reaction in a MeOH/H2O (9/1, v/v, pH = 7.4) medium and for H2S based on the addition reaction in EtOH/H2O (7/3, v/v, pH = 7.4) solution. In addition, L showed a fluorescence colorimetric response to Al3+ in the solid state. Furthermore, L was applied to detect Al3+ and H2S in actual water samples.

Highly selective fluorescent peptide-based chemosensors for aluminium ions in aqueous solution

Two novel fluorescent peptide-based chemosensors, including A (2-amino-benzoyl-Ser-Glu-Glu-NH₂) and B (2-amino-benzoyl-Ala-Glu-Pro-Glu-Ala-Glu-Pro-NH₂) were synthesized and characterized by nuclear magnetic resonance (NMR) spectra. These fluorescent probes exhibited excellent selective and sensitive responses to Al³⁺ ions over other metal ions in aqueous buffered solutions. The limits of detection for both chemosensors towards the Al³⁺ ions were in the order of ∼10^-7 M (A: 155 nM and B: 195 nM), which clearly indicates that these probes have significant potential for biological applications. They also displayed high binding affinity (1.3029 × 10⁴ M^-1 and 1.7586 × 10⁴ M^-1 relevant to A and B respectively). These two chemosensors are great analytical probes that produce turn-on responses upon binding to Al³⁺ ions through an intramolecular charge transfer (ICT) mechanism. In addition, the application of both chemosensors was examined over a wide range of pH. The fluorescent peptide-based probes and Al³⁺ form a 1:1 coordination complex according to the ESI-MS and Job's plot analysis. Notably, upon addition of Al³⁺ to these chemosensors, a fluorescence enhancement of approximately 8-fold was observed and the binding mode was determined using NMR titration and fluorescence emission data.

Application of real sample analysis and biosensing: Synthesis of new naphthyl derived chemosensor for detection of Al3+ ions

A new chemosensor (NANH) based on naphthyl moiety was synthesized with good selectivity and sensitivity towards Al³⁺ ions via the inhibition by operating through dual mechanisms like photo-induced electron transfer (PET) and excited-state intramolecular proton transfer (ESIPT). The synthesized NANH was validated by various techniques such as ¹H, ¹³C NMR and mass spectrum. While prominent fluorescent enhancement was observed from the NANH upon binding with Al³⁺ ions, however, other metal ions have not responded in the emission spectrum. Detection limit and association constant of NANH for Al³⁺ were calculated as 1.2 × 10^-7 M and 4.09 × 10⁴ M^-1 by using fluorescence titration method. Binding ratio (1:1) of NANH with Al³⁺ ions were proved by Job's plot and DFT studies. Furthermore, aluminium in variety of water samples was determined, and NANH could be used for biosensing of Al³⁺ in living cells.

A sensitive OFF–ON–OFF fluorescent probe for the cascade sensing of Al3+ and F− ions in aqueous media and living cells

A simple Schiff-base ligand 2-hydroxy-1-naphthaldehyde semicarbazone (HNS) was synthesized and characterized. Based on the combined effect of inhibition of CH Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> N isomerization and chelation-enhanced fluorescence (CHEF), HNS functions as a fluorescence “turn on” sensor for Al³⁺ in buffered aqueous media. Based on the strong affinity of Al³⁺ to F⁻ ions, the in situ generated Al³⁺–HNS complex can also be utilized as an effective chemosensor for F⁻ sensing by metal displacement approach, ensuing quenching of fluorescence by the reversible return of HNS from Al³⁺–HNS complex. Thus a method using a single probe for the detection of both Al³⁺ and F⁻ ions is developed. The system exhibits high selectivity and sensitivity for Al³⁺ and F⁻ ions and the detection limits were found to be as low as 6.75 × 10⁻⁸ M and 7.89 × 10⁻⁷ M, respectively. Furthermore, the practical applicability of this probe has been examined in living cells.

A simple Schiff-base ligand 2-hydroxy-1-naphthaldehyde semicarbazone (HNS) was synthesized and applied to the sequential sensing of Al³⁺ and F⁻ ions in aqueous media and live cells.

A novel fluorescent-colorimetric probe for Al3+ and Zn2+ ion detection with different response and applications in F- detection and cell imaging

A novel Schiff base fluorescence probe (HL) was synthesized by the condensation of salicylaldehyde and an 8-aminoquinoline derivative. This probe acts as a "turn-on" dual selectivity fluorescence probe for Zn²⁺ and Al³⁺ ions, providing different colors and detection limits (DL) of 11.5 and 23.5 nM, respectively. Moreover, when Zn²⁺ and Al³⁺ co-exist, HL exhibits a preference for Al³⁺ by displacing Zn²⁺ from the HL-Zn²⁺ complex, realizing a dual-channel signal output for Al³⁺. The HL-Al³⁺ system could further discern F^- by a "turn-off" fluorescence response with a DL of 86.0 nM. Furthermore, the probe HL was capable of monitoring intracellular Al³⁺, Zn²⁺ and F^- in living PC12 cells in vitro through fluorescence imaging, which proved its value in potential in vivo applications.

A new high selective and sensitive turn-on fluorescent and ratiometric absorption chemosensor for Cu2+ based on benzimidazole in aqueous solution and its application in live cell

A new benzimidazole base turn-on fluorescent and ratiometric absorption chemosensor (L) bearing bidentate ligand for detection of Cu²⁺ was designed and synthesized. Fluorescence and UV-vis spectra studies demonstrated that L can detect Cu²⁺ ions in aqueous solution using fluorescence enhancement and ratiometric absorption sensing over a wide pH range. Both fluorescent and ratiometric absorption sensing of L for Cu²⁺ possessed high selectivity and sensitivity over other competitive metal ions and had low detection limit. Job's plot, mass spectra and DFT calculation indicated the sensing mechanism is the complex formation between L and Cu²⁺ with 1:2 stoichiometry. Fluorescence images of HepG2 in the absence and presence of Cu²⁺ displayed L had cell permeability and detection ability for Cu²⁺ in live cells.

Ultrasensitive and highly selective detection of Cu2+ ions based on a new carbazole-Schiff

A new chemosensor for Cu²⁺ based on Schiff base with high sensitivity and selectivity was designed and synthesized. The fluorescence intensity of the chemosensor in CH₃CN solution was enhanced 160-fold after the addition of 10 equiv. Cu²⁺ over other metal ions. In addition, it also facilitates colorimetric detection for Cu²⁺ in CH₃CN solution. The chemosensor displayed low detection limit and fast response time to Cu²⁺.

A new fluorene-based Schiff-base as fluorescent chemosensor for selective detection of Cr3+ and Al3

2-((9H-fluoren-2-ylimino) methyl)phenol (F3) was synthesized by condensation reaction of 9H-fluoren-2-amine and 2-hydroxybenzaldehyde in EtOH and characterized by its melting point, ¹H-,¹³C NMR and molecular mass. F3 exhibits a high selectivity for detection of Cr³⁺ and Al³⁺ ions as a fluorescent chemosensor and showed a single emission band at 536nm upon excitation at 333nm according to fluorescence emission studies. The addition of Cr³⁺ and Al³⁺ make a significant increase in fluorescent intensity at 536nm in CH₃CN, while other metal ions have almost no influence on the fluorescence. The fluorescence enhancement was attributed to the inhibited CN isomerization and the obstructed excited state intra-molecular proton transfer (ESIPT) of compound F3. Job's plot and DFT calculations data showed that the binding stoichiometries of F3 with Cr³⁺ and Al³⁺ are 2:1. The association constants (K_a) for Cr³⁺ and Al³⁺ were calculated and found to be 8.33×10⁴M^-1 and 5.44×10⁴M^-1, respectively. The detection limits were also calculated for Cr³⁺ and Al³⁺ and found to be 2.5×10^-7mol/L and 3.1×10^-7mol/L, respectively.

A Unique Sensitive and Highly Selective Fluorescent Naphthodiaza-Crown Macrocyclic Ligand Chemosensor for Hg2+ in Water

The noticeable enhancement in fluorescence emission of O₂N₂-donor naphthodiaza-crown macrocyclic ligand (L) in the presence of Hg²⁺ was observed in which the fluorescence quantum yield of free ligand L as well as L/Hg²⁺ complex were found to be as 0.29 and 0.49, respectively. The observed ultra-low limit of detection (LOD) for Hg²⁺ by L was determined as low as 1.0 × 10^-11 M in water. A 1:1 stoichiometry was also established for L/Hg²⁺ together with a binding constant K _BH = 66,543 by employing fluorescence spectrophotometry. The competition experiments on L/Hg²⁺ demonstrated highly selective detection of Hg²⁺ in the presence of the library cations. A two path mechanism for detection of metal ion in terms of coordination of metal ion to L and/or the formation of counter ion was proposed by using of ¹H NMR and fluorescence spectroscopy. Graphical Abstract pH dependence mechanism of interaction between Hg²⁺ and macrocyclic ligand L.

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.

A ratiometric and selective fluorescent chemosensor for Ca(ii) ions based on a novel water-soluble ionic Schiff-base

A new, simple and water-soluble chemosensor, based on the ionic Schiff-base (ISB), 1-(4-hydroxy-3-((2-mercaptophenylimino)methyl)-5-methoxybenzyl)-4-methoxypyridiniumchloride (3), was synthesized and applied to fluorescently sense Ca(ii) ions.

A selective fluorescent probe based on bis-Schiff base for “turn-on” detection of Al3+and cysteine by different mechanisms

A novel fluorescent sensorLbased on phenolphthalein derivative bis-Schiff base for “turn-on” detection of Al³⁺and cysteine on different mechanisms.

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.