Schiff Base Research Articles

Proton conductivity amelioration of chitosan via novel Schiff base formation with oxidized polyvinyl alcohol for proton exchange membrane

Proton conductivity amelioration of chitosan via novel Schiff base formation with oxidized polyvinyl alcohol for proton exchange membrane

Synthesis and Crystal Structures of β -Diketonato Associated Aluminium Complexes as Potential Catalysts for the Ring-Opening Polymerization of ε-Caprolactone.

A couple of novel crystalline aluminium(III) derivatives containing tridentate Schiff base ligand (HL) and β-diketones (acetylacetone = acac, benzoylacetone = bnzac, dibenzoylmethane = dbnz) viz [Al(L)bnzac] [Al1], [Al(L)dnbz] [Al2] and [Al(L)acac] [Al3] were synthesized and characterized well using different spectroscopic techniques and elemental analysis. Single crystal X-ray diffraction (SCXRD) analysis of Al2 & Al3 exhibited hexacoordinated geometry around aluminium centre atom. The ring opening polymerization (ROP) of caprolactone (CL) was evaluated to determine the catalytic potential of the complexes Al1-Al3 in absence as well as in presence of benzyl alcohol. IEnd group study was performed using MALDI-TOF spectrometry and 1H NMR spectral analysis verified the existence of the -OBn group as an end group. First order kinetics were found in the monomer aligned with the activated monomer mechanism for the catalysts. Density functional theory (DFT) was carried out to optimize the geometries at B3LYP/LANL2DZ level.

Role of Furfural and 5-Methyl-2-furfural in Glucose-Induced Inhibition of 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) Formation in Chemical Models and Pork Patties

The effects of furfural and 5-methyl-2-furfural produced by the Maillard reaction on PhIP formation were investigated in chemical models and roasted pork patties. In the chemical models, the results indicated that increasing levels of furfural (r = −0.7338, R2 = 0.9557) and 5-methyl-2-furfural (r = −0.7959, R2 = 0.9864) significantly reduced PhIP formation, displaying a strong linear correlation. The effects of furfural and 5-methyl-2-furfural on the precursors of phenylalanine (Phe) and phenylacetaldehyde showed a significant reduction in the Phe level, while the level of phenylacetaldehyde was not increased. In addition, neither furfural nor 5-methyl-2-furfural could significantly reduce creatinine or PhIP. Further mechanism studies showed that furfural (5-methyl-2-furfural) directly captured Phe to form the corresponding Schiff base compounds a (2-((furan-2-ylmethylene) amino)-3-phenylpropanoic acid) and b (2-(((5-methylfuran-2-yl)methylene)amino)-3-phenylpropanoic acid). This process reduced the production of phenylacetaldehyde, thereby inhibiting the PhIP formation pathway. More importantly, these two compounds were detected in roasted pork patties to which glucose was added. The above pathway was finally confirmed in roasted pork patties. These results revealed that furfural and 5-methyl-2-furfural, formed during the Maillard reaction, play a significant role in inhibiting the formation of PhIP by reacting with Phe.

An easily synthesizable naphthalene-based sensing platform for Al3+ and Zn2+ ions: theoretical insights and live cells imaging.

A new naphthalene-derived Schiff base probe, 1-((2-(diphenylphosphino)ethylimino)methyl)naphthalen-2-ol (HL), has been demonstrated for fluorometric detection of Al3+ and Zn2+ ions. HL was characterized by elemental analysis, FT-IR, NMR, UV-Vis, fluorescence, and ESI-MS analyses. It exhibited high sensitivity and selectivity toward Al3+ and Zn2+ ions in a semi-aqueous medium (CH3CN-H2O; 4 : 1, v/v), remaining unaffected by other competing metal ions. As a 'turn-on' fluorogenic probe, HL displayed strong emission enhancements at 430 nm and 450 nm (λex 300 nm) upon the addition of Al3+ and Zn2+ ions, respectively, with detection limits of 0.62 μM for Al3+ and 0.54 μM for Zn2+. The addition of Al3+ caused ca. 20 nm blue-shift in emission and absorption maxima of HL due to strong complex formation. The calculated binding constant values were found to be 1.39 × 103 M-1 and 4.78 × 103 M-1, respectively, for Al3+ and Zn2+ ions. Job's plot, NMR, ESI-MS, and density functional theory (DFT) studies supported the metal ion binding mechanism with 1 : 1 stoichiometry. Fluorescence imaging experiments further revealed HL's ability to detect intracellular Al3+ in live cells with very low cytotoxicity, highlighting its potential as a selective chemosensory probe.

Synthesis, antibacterial activity, in silico ADMET prediction, docking, and molecular dynamics studies of substituted phenyl and furan ring containing thiazole Schiff base derivatives.

This study synthesized eighteen phenyl and furan rings containing thiazole Schiff base derivatives 2(a-r) in five series, and spectral analyses confirmed their structures. The in vitro antibacterial activities of the synthesized analogs against two gram-positive and two gram-negative bacteria were evaluated by disk diffusion technique. Compounds (2d) and (2n) produced prominently high zone of inhibition with 48.3 ± 0.6 mm and 45.3 ± 0.6 mm against B. subtilis, respectively, compared to standard ceftriaxone (20.0 ± 1.0 mm). However, the antibacterial potency of the compounds with furan ring was more notable than that of phenyl ring-containing derivatives. Molecular docking and dynamic study were performed based on the wet lab outcomes of (2d) and (2n), where both derivatives remained in the binding site of the receptors during the whole simulation time with RMSD and RMSF values below 2 nm. In silico ADMET prediction studies of the synthesized compounds validated their oral bioavailability. A more detailed study of the quantitative structure-activity relationship is required to predict structural modification on bioactivity and MD simulation to understand their therapeutic potential and pharmacokinetics.

Study of DFT, Synthesis, and Nonlinear Optical Properties of a Schiff Base Compound.

A Schiff base (LS2) compound is synthesized via a reaction of a hot ethanolic solution of (3-ethoxy salcyaldehyde) and a hot ethanolic solution of amine(methyl-4-amino benzoate). The LS2 compound is characterized via 1H and 13C NMR spectra, Mass spectrum, and FT-IR spectrum. We observed multiple diffraction patterns of a cw 473nm laser beam from the LS2 compound caused by spatial self-phase modulation (SSPM). The nonlinear refractive index (NLRI) of the LS2 compound is estimated at the high-power input of the laser beam and found equals to 5.387 × 10-7 cm2/W. The Z-scan techniques are used to estimate the NLRI and found equals to 0.12 × 10-7 cm2/W. The all-optical switching (AOS) effect can be seen when 473nm is used as the controlling beam and 532nm is used as the controlled beam.

Bismuth(III) complexes of Schiff bases derived from aliphatic amines: interaction with biomolecules and antimicrobial activity.

Schiff bases bearing a sterically hindered phenolic moiety and their Bi(III) complexes were synthesized and characterized by physicochemical, quantum chemical, and biological methods. The compounds were screened in vitro against bacterial and yeast strains. It was found that Bi(III) complexes demonstrate higher antimicrobial activity compared to the parent ligands as well as to the commonly used drug (De-Nol®). Moreover, the antibacterial activity of investigated compounds did not directly correlate with their hemolytic activity, indicating that the antimicrobial effect of Bi(III) complexes cannot be explained solely by their membranolytic properties. Spectrofluorometric studies of the interaction of the Bi(III) complexes with plasma proteins indicate their moderate to high affinity toward BSA and hemoglobin, which is crucial for the determination of their pharmacological profile as well as toxicity assessment. Additionally, molecular docking was performed to predict the possible interaction modes and binding energies of the tested compounds at the molecular level. The results obtained may provide the basis for the design and development of novel Bi(III)-based antimicrobial agents.

In‐situ Chemical Bonded Tubular Titanium Dioxide With Covalent Organic Frameworks Promoted Photocatalytic Activity

AbstractSolar driven water splitting to produce hydrogen is an ideal way to generate renewable energy, however, there is still a challenge of photo generated charge recombination. Herein, on the basis of unique tubular titanium dioxide (TiO2), covalent organic frameworks (COFs) are grown in situ and linked through chemical bonds to obtain heterojunction materials. The results show that when the Schiff base covalent organic frameworks (COF‐1) loading is 30% (30% COF‐1/TiO2), the photocatalytic hydrogen evolution rate (HER) of the composite material is as high as 31.9 mmol/g/h, which was twice that of the original TiO2 and 2.6 times that of the original COF‐1. Experimental characterization demonstrates that the tubular heterojunction (COF‐1/TiO2) can improve the migration of electron‐hole pairs and enhance the utilization efficiency of charge carriers. This provides new insights into the design of efficient photocatalytic materials.

Green catalytic synthesis of 5‐hydroxymethyl‐2‐furancarboxylic acid in a gram scale over schiff base polymer supported silver‐nanoparticle catalysts

Here, a series of schiff‐base porous organic polymer‐supported silver‐nanoparticle, Ag0 NPs@PPTA‐x were prepared with a two‐step ion coordination/hydrogen reduction. The resulting composite Ag0 NPs@PPTA‐9.08 shows excellent catalytic performance for HMF oxidation to HMFCA, and an impressive HMFCA yield of 99.3% was achieved under optimal condition (NaOH 1.5 eq, 50 mL/min air flow, 20 °C, 6 h). Analysis techniques such as ICP‐OES, XRD, TEM, SEM, N2 adsorption‐desorption, and XPS were employed to characterize the structure and properties of Ag0 NPs@PPTA‐x. The results indicate that the coordination of the nitrogen atom is the key factor for the higher activity and stability of Ag0 NPs@PPTA‐9.08. The results of leaching and reusing tests as well as structural characterization (XRD, SEM, and FT‐IR) shows that the Ag0 NPs@PPTA‐9.08 has good stability and robustness structure. Furthermore, a gram‐scale oxidation of HMF indicates this catalytic system can be readily scaled up to an industrial level. Finally, the results of other aldehydes oxidation over Ag0 NPs@PPTA‐9.08 indicate the good substrate adaptability of the Ag0 NPs@PPTA‐9.08. This work provides a new method for stabilizing nano‐silver catalysts and opens up a simple avenue to selective oxidation of aldehydes that easily to scaled up.

High Proton Conductivity Enhancement Obtained by a Covalent Postsynthesis Modification Approach for Two Metal-Organic Frameworks.

This study demonstrates an effective strategy to enhance proton conductivity by synthesizing 2 three-dimensional metal-organic frameworks (MOFs), [Zn(DTD22)]n (MOF 1) and [Cd2(DTD22)2]n (MOF 2), (DTD22 = 4,4″-diamino-[1,1':4',1″-terphenyl]-2,2″-dicarboxylic acid). The DTD22 ligand used formed a continuous hydrogen-bonding network in the structure, constructing excellent hydrophilic channels. MOF 1 and MOF 2 were further postsynthesized and modified (PSM) by Schiff base reaction, and 4-chloro-3-formylbenzenesulfonic acid ligands containing -SO3H and -Cl were successfully introduced into the framework to form PSM-MOF 1 and PSM-MOF 2. Experiments showed that this modification significantly enhanced the proton conductivity of the materials, especially at 90 °C and 98% RH: PSM-MOF 1 (2.38 × 10-1 S·cm-1) and PSM-MOF 2 (3.50 × 10-1 S·cm-1). In comparison, the conductivities of unmodified MOF 1 and MOF 2 were 8.55 × 10-2 S·cm-1 and 9.50 × 10-5 S·cm-1, respectively. The present study demonstrates that the proton conductivity of MOFs can be effectively enhanced by the covalent postmodification method, which provides a new idea for the application of MOFs.

Physicochemical Characterization of One-Pot Synthesized 2-[(E)-(4-Hydroxyphenylimino)methyl]phenol Schiff Base Using Orange Juice as Citrus-Derived Acidic Medium

Physicochemical Characterization of One-Pot Synthesized 2-[(E)-(4-Hydroxyphenylimino)methyl]phenol Schiff Base Using Orange Juice as Citrus-Derived Acidic Medium

Preparation and sensing properties of fluorescent hydrogel based on chitosan modified with fluorene moiety

A novel fluorescent chitosan-based hydrogel (CFC) incorporating varying amounts of conjugated fluorene units was synthesized by grafting fluorene derivatives containing bisaldehyde groups onto chitosan through the Schiff base reaction. The resulting xerogels exhibited a uniform mesh structure attributed to the cross-linking of fluorene moieties. With the incorporation of fluorene, the chitosan-based hydrogels demonstrated gel-like properties, showing an increase in both energy storage modulus and loss modulus as crosslink density increased. Furthermore, enhanced crosslink density contributed to improved hydrophilicity of the gel and the contact angle was as low as 65.5°. These modified hydrogels modified with fluorene units showed good thermal stability and the thermal decomposition temperature of the hydrogel was approximately 250 °C. The hydrogels displayed blue-green fluorescence with double peak emission near about 440 nm and 500 nm, which originated from π-π* transition of the conjugated fluorene derivative structure and intramolecular charge transfer (ICT) process, respectively. The fluorescence intensity of the hydrogels increased with the fluorene grafting amount. The quantum yield reached a maximum of 0.120, demonstrating the effectiveness of the modification. In this study, the detection limit for Fe³+ ions was 10 ppm, surpassing most similar studies. These hydrogels hold significant potential for applications in metal ion detection.

Starfish-Inspired Synergistic Reinforced Hydrogel Wound Dressing: Dual Responsiveness and Enhanced Bioactive Compound Delivery for Advanced Skin Regeneration and Management.

Effective wound management demands advanced dressings that protect while actively supporting healing. Traditional wound dressings often fall short of meeting the complex needs of skin repair. Inspired by the regenerative abilities of starfish, we developed a bionically engineered hydrogel designed to enhance wound healing. The hydrogel is synthesized through the coassembly of dopamine-modified cellulose nanofibers, chitosan, (3-aminobenzeneboronic acid)-grafted oxidized dextran, and poly(vinyl alcohol), utilizing dynamic Schiff base and boronic ester linkages. This innovative design imparts multifunctional properties, including injectability, 3D printability, antibacterial activity, self-adhesion, self-healing, antioxidant protection, and hemostasis, which emulate the defense mechanisms and regenerative processes of starfish. These characteristics work synergistically to reduce infection and oxidative stress and improve healing efficiency. Additionally, the hydrogel incorporates mangiferin and Vitamin C, which are released in a controlled manner in response to the wound's microenvironment (pH and reactive oxygen species), promoting tissue regeneration and reducing inflammation. In vitro tests confirmed its dual responsiveness, while finite element modeling validated the controlled release of bioactive compounds. In vivo testing on a rat full-thickness wound model showed a 100% healing rate by day 13, significantly outperforming commercial alternatives. The hydrogel's nontoxicity and advanced healing capabilities make it a promising solution for patients with critical healing needs, offering a comprehensive integration of natural biological processes and cutting-edge engineering.

Synthesis and characterization of rare earth metal complexes with novel Schiff base

Objectives. The work set out to synthesize Schiff base ligands containing a hydrazone moiety of (Z)-2-((E)-1-hydroxyethylidene)hydrazineylidene)-2-phenylacetic acid, as well as their praseodymium, samarium, europium, and gadolinium complexes, and to study their structure.Methods. The structure of ligands was identified by infrared (IR), ultraviolet (UV), and nuclear magnetic resonance (NMR) spectroscopy. The structure of the complexes was confirmed by elemental analysis, IR and UV spectroscopy, and thermogravimetric analysis.Results. The Schiff base ligands containing a hydrazone moiety of (Z)-2-((E)-1-hydroxyethylidene)hydrazineylidene)-2-phenylacetic acid, as well as their praseodymium, samarium, europium, and gadolinium complexes, were synthesized using the authors’ procedure.Conclusions. NMR and IR spectroscopic data confirm that the Schiff base ligand is in the keto form. There are three absorption bands in the wavelength range of 205–306 nm in the UV spectrum of the ligand. A bathochromic shift is observed in the spectrum of all complexes. The molar ratio of ligand and metal in the complexes was 3 : 1.

Photo- and Schiff Base-Crosslinkable Chitosan/Oxidized Glucomannan Composite Hydrogel for 3D Bioprinting

Chitosan is an attractive material for developing inks for extrusion-based bioprinting of 3D structures owing to its excellent properties, including its mechanical properties and antimicrobial activity when used in wound dressings. A key challenge in formulating chitosan-based inks is to improve its gelation property to ensure reliable printing and the mechanical stability of the printed structures. To address these challenges, this article presents a novel chitosan/oxidized glucomannan composite hydrogel obtained through the combination of Schiff base and phenol crosslinking reactions. The proposed biomaterial forms soft hydrogels through Schiff base crosslinking, which can be further stabilized via visible light-induced phenol crosslinking. This dual-crosslinking approach enhances the printability and robustness of chitosan-based ink materials. The proposed chitosan/oxidized glucomannan hydrogel exhibits excellent extrudability and improved shape retention after extrusion, along with antimicrobial properties against Escherichia coli. Moreover, good cytocompatibility was confirmed in animal cell studies using mouse fibroblast 10T1/2 cells. These favorable features make this hydrogel highly promising for the extrusion-based bioprinting of complex 3D structures, such as tubes and nose-like structures, at a low crosslinker concentration and can expand the prospects of chitosan in bioprinting, providing a safer and more efficient alternative for tissue engineering and other biomedical applications.

Synthesis, Structure and Photophysical Properties of Dinuclear Zinc(II) Complexes with Schiff Base Bearing p-Phenylenediamine.

Four new dinuclear complexes Zn1-Zn4 were synthesized by the interaction of Zn(NO3)2.4H2O with Schiff bases containing p-phenylenediamine. The data of ESI-MS, IR and 1H NMR spectroscopy showed that the ligands coordinated with Zn(II) via two sets of O, Nimine atoms. In DMSO, ligands exhibit weak luminescence while the complex solutions emit strongly at maximum wavelength in the range 409-513nm. Notably, electron-donating groups enhance the quantum yield of the complex solutions. Particularly, Zn2 containing NEt2 substitutes has outstanding quantum yields of 74%. Besides, the lifetimes of the complexes increase in the order Zn2 < Zn4 < Zn1 < Zn3 in DMSO. Along with the experiment, the structure, absorption and emission spectra of Zn1-Zn4 have been investigated by TD-DFT calculation. The result reproduces well the experimental absorption wavelengths and shows that the absorptions of the complexes are due to the singlet S0 → S1* transition from the π to the π* orbital of the ligand in complexes and the emission occurs from minimum of the S1 state to the ground singlet state S0. The calculation results also support for the fact that Zn2 has profoundly quantum yields.

New Schiff Base Clubbed Benzothiazole Derivatives: Design, Synthesis, Biological Evaluation, Molecular Docking and Pharmacokinetic Studies as Antibacterial and Antifungal Agents

New Schiff Base Clubbed Benzothiazole Derivatives: Design, Synthesis, Biological Evaluation, Molecular Docking and Pharmacokinetic Studies as Antibacterial and Antifungal Agents

Structural Characterization, XRD, DFT Calculations, Docking, Antimicrobial, Anticancer Applications, and Electrochemical Performance Studies of Some New Schiff Base Transition Metal Complexes

ABSTRACTThe condensation of 3‐amino‐1H‐1,2,4‐triazole with 2‐benzoyl benzoic acid produced a novel Schiff base ligand (H2L). The structure of synthesized H2L and its metal complexes [Co(II), Ni(II), Cu(II), and Zr(IV)] were characterized by mass spectrometry, FT‐IR, 1H NMR, XRD, UV‐vis, ESR, and TG‐DTG analyses also, supported by computational approaches. FT‐IR spectral data showed that H2L acts in a tridentate mode through azomethine nitrogen, the nitrogen of triazole, and carboxylate group oxygen. XRD results indicated that compounds were polycrystalline with monoclinic systems for H2L, Co(II), and Cu(II) compounds but orthorhombic systems for Zr(IV) and Ni(II) complexes. Coats–Redfern and Horowitz–Metzger equations were utilized. The optical characteristics of compounds were evaluated. From DFT, ΔE values of our complexes varied from 0.033 eV for the more reactive Co(II) complex to 0.109 eV for the less reactive Zr(IV)complex compared to H2L (0.113 eV). Also, from σ values, complexes were considered soft compared to H2L. The optical band gap (Eg) values were compared to those produced by DFT and found to be equivalent. H2L and its metallic complexes were assessed for their antibacterial activity as well as their antifungal activity. The results indicated that the complexes exhibited significant antimicrobial efficacy. H2L and its metal complexes were evaluated for cytotoxic activity against the ATB‐37 colon cancer cell line. Notably, the Ni(II) and Cu(II) complexes exhibited significant cytotoxic effects than other compounds. H2L and its complexes were subjected to molecular docking into TRK (PDB: 1t46), DHFR (PDB: 2W9H), PaaABC (PDB: 4IIT), and NatB (PDB: 5K04) to predict the activity or help in interpretation their cytotoxicity and antimicrobial potential. The electrochemical behavior of the metal complex–modified electrodes was assessed through cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) measurements, all performed in a 6‐M KOH electrolyte. The results showed that Ni(II) complex–modified electrodes have much higher capacitance than other modified electrodes.

Chemical Modifications of Chitin and Chitosan Fibers and Filaments: A Review

AbstractThis review examines the chemical modifications of chitin and chitosan fibers and filaments, emphasizing their potential for diverse applications. It discusses a variety of modifications, including amidoximation, acetylation, partial deacetylation, N‐maleation, N‐naphthaloylation, N‐halamination, grafting, oxidation, phosphorylation, sulfation, N‐acylation, Schiff base formation, quaternization, nucleophilic substitution, hydroxyethylation, and ureidation transformations. These modifications significantly enhance the properties of chitin and chitosan, improving their solubility, dispersibility, hydrophobicity, environmental stability, mechanical strength, antimicrobial activity, and hemostatic capabilities, among other characteristics. By strategically tailoring these biopolymers through chemical modifications, novel materials with enhanced functionalities can be synthesized. These advanced materials are crucial for developing functional products with broad applications across various fields, spanning from biomedicine to sustainable composites.

DNA Binding Affinities and Antimicrobial Activities of Pd(II) Complexes of Chromone Schiff Bases

ABSTRACTPalladium complexes of the novel halogenated Schiff bases bearing chromone and antipyrine heterocyclic rings were conventionally synthesized. Their structural characterization was done by mass spectrometry, FT‐IR, electronic, and 1H‐NMR spectral techniques. The metal complex stoichiometry was found to be 1:1 having a square planar geometry. The intercalative binding between CT‐DNA and the novel palladium complexes was investigated by using absorption, emission spectroscopy, and viscometry. These complexes also revealed antibacterial activity against Escherichia coli and Staphylococcus aureus and antifungal activity against Macrophomena species.