Schiff Base Research Articles

Preparation of chitosan‐based macromolecular synergistic antioxidants containing hindered phenolic and secondary amine structures and its effects on thermo‐oxidative aging of styrene‐butadiene rubber/silica composites

AbstractIn this study, chitosan (CS)‐based macromolecular synergistic antioxidant CS‐UC‐TDAA containing carbon–carbon double bond, hindered phenol, and aromatic secondary amine was prepared by using CS,10‐undecenoyl chloride (UC), p‐aminobenzoic acid (AA), 3,5‐di‐tert‐butyl‐2‐hydroxybenzaldehyde (TD) via esterification, Schiff base reaction, and acylation reaction. The molecular structure of CS‐UC‐TDAA was characterized by fourier transform infrared, 1H NMR, and elemental analysis. The effects of macromolecular synergistic antioxidant CS‐UC‐TDAA, small molecular antioxidant TDAA, commercial antioxidant 4020, and butylated hydroxytoluene (BHT) on the antiaging properties of styrene‐butadiene rubber (SBR)/SiO2 composites were systematically studied by accelerated thermo‐oxidative aging test, thermogravimetric (TG) analysis, and methanol Soxhlet extraction experiment. The experimental results show that CS‐UC‐TDAA has more outstanding thermo‐oxidative aging resistance, thermal stability, and solvent extraction resistance in SBR/SiO2 composites than TDAA, 4020, and BHT. The macromolecular synergistic antioxidant CS‐UC‐TDAA endows SBR/SiO2 composites with more durable antiaging performance, which is attributed to the synergistic antioxidant effect of its hindered phenol and aromatic secondary amine groups. Additionally, its resistance to migration and extraction is facilitated by the crosslinking of the carbon–carbon double bond with the rubber and its substantial molecular weight.

A hydroxyl-rich covalent organic framework for the precisely selective fluorescence sensing of explosives with high sensitivity

Covalent organic Frameworks (COFs) have become a new platform for functional research and material design. A novel covalent organic skeleton (DHB-TFP COF) was synthesized from 2-hydroxybenzene-1,3,5-tricarbaldehyde and 3,3′-dihydroxybenzidine using Schiff base reaction. DHB-TFP COF is a highly stable porous crystalline material and exhibits exceptional thermal and chemical resistance. DHB-TFP COF exhibited a selective and sensitive “turn-off” fluorescence response to 4-NP in ethanol, and TNP not only significantly quenched the fluorescence of DHB-TFP COF but also caused the obvious red-shift. The fluorescence intensity of DHB-TFP COF exhibited a linear correlation with the concentration of 4-NP with a detection limit of 0.40 μM. Furthermore, the maximum fluorescence peak observed for DHB-TFP COF demonstrated a linear relationship with TNP concentration with a detection limit of 11.15 μM. DHB-TFP COF exhibited satisfactory recovery in the detection of 4-NP and TNP in actual water sample indicating its practical application potential. The O atoms of rich hydroxyl and N atoms of C = N present on the surface of DHB-TFP COF scaffold can establish strong hydrogen bonds with 4-NP and TNP, facilitating their mutual interaction. The spectra studies indicated that the fluorescence quenching mechanism can be attributed to the absorption competitive quenching (ACQ) and fluorescence resonance energy transfer (FRET) mechanism. This study not only proposed the approach for synthesizing novel structured organic frameworks, but also developed a highly selective and sensitive fluorescence chemical sensor for identifying and detecting 4-NP and TNP.

Aminoquinoline-based ruthenium(II) and iridium(III) polypyridyl complexes: Investigating potential photosensitisers for cancer treatment via photodynamic therapy

Cancer is a devastating noncommunicable disease that remains one of the most pressing health challenges of the twenty-first century. Chemotherapy stands as one of the most common and effective cancer treatment methods. However, severe side effects and acquired drug resistance in many cancers have significantly diminished the efficacy of current chemotherapeutic agents. The urgent demand for novel treatment modalities has led to the development of photodynamic therapy (PDT) for the treatment of various cancer types. In this work, the synthesis of aminoquinoline-based transition metal complexes containing two PGMs (Ir(III) and Ru(II)) as potential photosensitisers is described. Mononuclear N,N-chelated Ru(II) and Ir(III) transition metal complexes were synthesized by reacting 4-aminoquinoline Schiff base ligands, which contain either a pyridyl or a quinolyl entity. The photostable Ru(II) and Ir(III) polypyridyl complexes were investigated for their potential use as PDT agents. In vitro cytotoxicity screenings conducted against a melanoma cell line (501mel) both in the absence and presence of light confirmed that all complexes demonstrated increased biological activity when exposed to visible light at 455 nm. Overall, the Ru(II) complexes are superior phototoxic agents in comparison with their Ir(III) congenors.

Biodegradable chitin nanofiber-alginate dialdehyde hydrogel: An injectable, self-healing scaffold for anti-tumor drug delivery

Injectable hydrogels fabricated from natural polymers have attracted increasing attentions for their potential in biomedical application owing to the biocompatibility and biodegradability. A new class of natural polymer based self-healing hydrogel is constructed through dynamic covalent bonds. The injectable self-healing hydrogels are fabricated by introducing alginate aldehyde to form Schiff base bonds with the chitin nanofibers. These hydrogels demonstrate excellent self-healing properties, injectability, and pH-responsive sol-gel transition behaviors. As a result, they can serve as carriers to allow an effective encapsulation of doxorubicin (DOX) for drug delivery. Furthermore, these hydrogels exhibit excellent biocompatibility and degradability in vitro and in vivo. The sustained release of DOX from the hydrogels effectively suppresses tumor growth in animal models without causing significant systemic toxicity, suggesting their potential application in anti-tumor therapies.

Bidirectionally regulated synthetic ferrocene-based aminal-linked porous organic polymer artificial enzyme towards photothermal-amplified synergistic antibacterial and wound healing therapy

Development of hetero-atom rich porous organic polymers (POPs) in facile and easy accessible methods are of significant importance to broad application potentials and enrich diversity of such materials. Here, a bidirectional adjustment strategy, starting with amino and aldehyde monomers, concurrently, was used for the rational preparation of N-rich aminal-linked POPs with customized structure and function. Five novel ferrocene-based aminal-linked POPs, were facilely fabricated via the one-pot catalyst-free Schiff base polycondensation between the 1,1′-Ferrocene dicarboxaldehyde and different types of triazine-bearing monomers with diverse geometrical features and functions (Porphyrin, cationic viologen, Ferrocene, 1,4,7,10-tetraazacyclododecane, and benzyl). The concurrent introduction of Ferrocene (redox-active) and triazine-Porphyrin (photoactive) endowed remarkable mimicking peroxidase-like activity and excellent photothermal and photodynamic activity with Fc-TDPP, which could be used as a broad spectrum fungicide, exerting photothermal enhanced photodynamic and enzyme antibacterial therapy. Notably, in vitro and in vivo experiments confirmed Fc-TDPP could not only kill S. aureus and E. coli quickly and efficiently, but also significantly accelerate the repairing of open wounds with S. aureus-infection. The as-proposed strategy are available for the low-cost constructing N-rich POPs with specific structure and functions targeted for wide potential applications in various fields.

Coordination number impact on magnetic properties of Schiff base Co(II) complexes

Two mononuclear Co(II) complexes with a tetrahedral and octahedral coordination geometry with a Schiff base ligand L− (anion of 4-[(2-fluoroanilino)-phenyl-methylene]-5-methyl-2-phenyl-pyrazol-3-one) having the formulas [CoL2]·2MeCN (1) and [CoL2(H2O)2]·2MeCN (2) have been synthesized and structurally characterized. Notably, their coordination geometry and magnetic relaxation behaviors can be tuned by variation of reaction conditions. Static magnetic studies reveal that complex 1 exhibits considerable easy-axis magnetic anisotropy. Frequency-dependent susceptibility measurements revealed slow magnetic relaxation behavior with spin-reversal barriers of 79.2 K at an applied external field of 500 Oe. Clear magnetic hysteresis loops were observed for 1 at 2 K. Complex 2 show field-induced slow magnetic relaxation with Raman and direct relaxation processes. The observed magnetic behavior of 1 and 2 is confirmed by high-level ab initio calculations and simulation of χMT(T) curves.

Injectable bio-multifunctional hyaluronic acid-based hydrogels loaded with poly ADP-ribose polymerase inhibitors for ovarian cancer therapy

The recent use of PARP inhibitors (PARPi) in the maintenance treatment of ovarian tumor has significantly improved the survival rates of cancer patients. However, the current oral administration of PARP inhibitors fails to realize optimal therapeutic effects due to the low bioavailability in cancerous tissues, and often leads to a range of systemic adverse effects including hematologic toxicities, digestive system reactions, and neurotoxicities. Therefore, the demand for an advanced drug delivery system that can ensure effective drug administration while minimizing these unfavorable reactions is pressing. Injectable hydrogel emerges as a promising solution for local administration with the capability of sustainable drug release. In this study, we developed an injectable hydrogel made from aminated hyaluronic acid and aldehyde-functionalized pluronic127 via Schiff base reaction. This hydrogel exhibits excellent injectability with short gelation time and remarkable self-healing ability, and is applied to load niraparib. The drug-loaded hydrogel (HP@Nir hydrogel) releases drugs sustainably as tested in vitro as well as displays significant anti-proliferation and anti-migratory properties on human epithelial ovarian cancer cell line. Notably, HP@Nir hydrogel effectively suppresses the growth of ovarian cancer, without significant adverse reactions as demonstrated in animal studies. Additionally, the developed hydrogel is gradually degraded in vivo for around 20 d, while maintaining good biocompatibility. Overall, the injectable hydrogel loaded with niraparib provides a secure and efficient strategy for the treatment and management of ovarian cancer.

Organoruthenium metallocycle induced mutation in gld-1 tumor suppression gene in JK1466 strain and appreciable lifespan expansion

Four Ru(II) complexes (A2-A5) were synthesized from the reaction of coumarin Schiff base ligands (7da2-tsc, 7da3-mtsc, 7da4-etsc and 7da5-ptsc) with [RuHCl(CO)(PPh3)3]. The compounds were characterized by FT-IR, UV–Vis, 1H, 13C and 31P NMR, mass spectrometry and crystallographic analysis. Calf Thymus DNA (CT-DNA) binding studies revealed the intercalative mode of binding of the complexes with DNA. The results of Bovine serum albumin (BSA) binding studies established the interaction between BSA followed static quenching mechanism. The cytotoxic effects of the complexes and the ligands were evaluated against breast (MCF-7 and MDA-MB-231) and lung carcinoma cell lines (A549 and NCI-H460) using MTT assay. Complex A4 demonstrated potent cytotoxic effects on both breast and lung cancer cells. Furthermore, morphological observations and FACS analysis showed the decrease in cell density by complex A4 by induced morphological changes and apoptotic body formation and cell death in both breast and lung cancer cells. Moreover, the invertebrate model Caenorhabditis elegans was employed to assess the in vivo anticancer activity of compound A4. The findings indicated that the treatment with A4 reduced tumor development and significantly extended organismal lifespan by 64 % in the tumoral strain JK1466 without adversely affecting essential physiological functions of the worm. Additionally, A4 demonstrated an upregulation of two crucial antioxidant defense genes. Overall, these results suggested that the compound A4 can be a potential candidate with novel chemotherapeutic applications.

An injectable and retrievable bioartificial pancreas fabricated by time-sequentially assembling islets-laden microgels for minimally invasive treatment of type 1 diabetes

Islets transplantation is a promising method to treat type 1 diabetes. Unfortunately, current islet encapsulation and transplantation strategies are difficult to simultaneously achieve the minimally invasive transplantation, rapid mass transportation, accurate positioning, long-term stability and easy retrieval. Herein, we present a novel strategy for islet encapsulation and transplantation that integrates the advantages of microencapsulation and macroencapsulation. Specifically, islets are first encapsulated in methacrylated carboxymethyl chitosan (CMCSMA) microgels by droplet microfluidic technology, and then oxidized sodium alginate-succinimide ester (OSA-NHS) as the assembling agent is added to time-sequentially assemble the islets-laden microgels. The as-formed microgel assembly (MA-CHO/NHS), or namely bioartificial pancreas, is injectable before transplantation due to the quick formation of dynamic Schiff base bonds, and becomes quite stable after transplantation with the slow formation of stable amide bonds.In addition, the interconnected micropores inside the microgel assembly is beneficial for mass transportation, and the abundant aldehyde and succinimide ester groups on assembling agent ensures good tissue adhesion. This injectable, tissue-adhesive, microporous, positionable and retrievable bioartificial pancreas can reverse the blood glucose levels of diabetic mice from hyperglycemia to normoglycemia for at least 90 days, and thus shows a broad application prospect in the field of diabetes treatment.

Laminated dihydrazone Zn(II) coordination polymer with prospects for sensory and multifunctional biomedical applications

This study introduces a new laminated coordination polymer, {[Zn3(HL)2(H2O)6](SO4)2⋅1.5dmf·2.5H2O}n (1), synthesized through the direct interaction of ZnSO4·7H2O with dihydrazone Schiff base ligand (H2L) at room temperature. Comprehensive characterization of the compound, employing various methods (SCXRD, PXRD, IR, TGA) revealed different coordination surrounding of metal atoms and a combination of photoluminescent properties and biological activity. The polymeric layers are corrugated along the b-axis, mutually intertwined forming channels filled with outer sphere anions (SO42-) and solvent molecules (water and dmf). It was shown that solvent molecules have a decisive influence on the photoluminescent properties of the compound. The partial removal of water molecules leads to increased photoluminescence, the intensity of which doubles compared to the synthesized crystals. Furthermore, the compound demonstrates robust antibacterial effects against four Gram-positive and two Gram-negative bacteria. In addition, its impact on cell proliferation, both in cancerous and non-cancerous cells, reveals the compound's antiproliferative effect on breast cancer cells in vitro, coupled with biocompatibility with human fibroblasts. This multifaceted approach positions the synthesized polymer as a promising candidate with vast potential for applications in luminescent materials and biomedical research

Synthesis, Molecular Docking, and antibacterial evaluation of Quinoline-Derived Ni(II), Cu(II) and Zn(II) complexes

We hereby report the synthesis of novel Ni(II), Cu(II) and Zn(II) complexes of (E)-2-(((7-chloro-2-hydroxyquinolin-3-yl)methylene)amino)-3-methylbutanoic acid ligand obtained by reacting 2,7-dichloroquinoline-3-carboaldehyde and amino acid, valine for antibacterial applications. The ligand and the metal complexes were characterized using FT-IR, UV–Vis, TGA/DTA, pXRD spectroscopic techniques and density functional theory (DFT) calculations. The Schiff base ligand was tridentate with ONO active binding sites as confirmed from its FT-IR spectral analysis. Disc diffusion method was used to assess the antibacterial potential of the Schiff base ligand and its metal complexes. The Schiff base ligand shows antibacterial activities of 8.33 ± 0.471 mm at concentration of 100 µg/ml and 9.33 ± 0.471 mm at concentration of 200 µg/ml against S. aureus. However, the copper complex exhibited zone of inhibition of 11.50 ± 0.408 mm at concentration of 100 µg/ml and 12.67 ± 0.471 mm at concentration of 200 µg/ml against S. aureus. This indicates that the copper complex has better antibacterial activity than the free Schiff base ligand. The overall result revealed the promising potential of the metal complexes for application as antibacterial agents. The DFT calculated absorption spectra agree with the corresponding experimental results. The molecular docking analyses also provided important insights on the interaction of the synthesized complexes with the target proteins.

Fluorometric and naked eye detection of cadmium ion by reduced Schiff base zinc-based probe in potable water: Theoretical and experimental approach

Alarmingly increasing population and industrial growth has immensely affected water bodies and potable water sources by elution of many heavy toxic metal ions, including cadmium (II). The rising threat has demanded easy and cost-effective detection of this heavy metal ion so as to spread widely across the masses and eliminate the poisoning of water. With this aim, we have synthesized a zinc-based fluorescent probe (rBDZn) having reduced Schiff base backbone with N- and O- donor atoms derived from 5-bromosalicaldehyde and 2,2-dimethylpropane-1,3-diamine, characterized with the aid of single crystal X-ray analysis, revealing a trimeric structure linearly bridged by azide ion. The complex has been found to exhibit a cyan blue fluorescence getting ‘turned-off’ in the presence of cadmium ion selectively along with many other cations in the aqueous solution together with a naked-eye visible color change from pale yellow to colorless. Steady-state and time-resolved fluorescence titration, and absorption titration experiments were performed. During the investigation of the sensing pathway it is observed that the detection of Cd2+ is being associated with the formation of the cadmium complex rBDCd from the probe rBDZn and this has been explained though a probable mechanism. In support of the fact a single crystal of Cd-substituted complex have been isolated and verified with single crystal XRD and computational calculations. Proper justification of the selectivity of the probe towards cadmium ion with a very low detection limit of 1.72 nM enables its genuine impact in the pollution management.

Chitosan-based GOx@Co-MOF composite hydrogel: A promising strategy for enhanced antibacterial and wound healing effects

A novel composite hydrogel was synthesized via Schiff base reaction between chitosan and di-functional poly(ethylene glycol) (DF-PEG), incorporating glucose oxidase (GOx) and cobalt metal-organic frameworks (Co-MOF). The resulting CS/PEG/GOx@Co-MOF composite hydrogel was characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and energy-dispersive X-ray spectroscopy (EDS). The results confirmed successful integration and uniform distribution of Co-MOF within the hydrogel matrix. Functionally, the hydrogel exploits the catalytic decomposition of glucose by GOx to generate gluconic acid and hydrogen peroxide (H2O2), while Co-MOF gradually releases metal ions and protects GOx. This synergy enhanced the antibacterial activity of the composite hydrogel against both Gram-positive (S. aureus) and Gram-negative bacteria (E. coli), outperforming conventional chitosan-based hydrogels. The potential of the composite hydrogel in treating wound infections was evaluated through antibacterial and wound healing experiments. Overall, CS/PEG/GOx@Co-MOF hydrogel holds great promise for the treatment of wound infections, paving the way for further research and potential clinical applications.

Synthesis and characterization of a Pd Schiff base complex anchored on Fe3O4 as a novel and recyclable catalyst for C-C cross-coupling reactions

Synthesis and characterization of a Pd Schiff base complex anchored on Fe3O4 as a novel and recyclable catalyst for C-C cross-coupling reactions

Investigating the Antibacterial Potential of Novel N-Boc Isatin Schiff Bases: Combining Synthesis with In-vitro and In-silico Studies

The abstract explores into the antibacterial efficacy of newly synthesized N-Boc isatin Schiff bases against a range of pathogenic bacteria, including multidrug-resistant strains. The characterization of the synthesized compounds was achieved through various spectroscopic methods including 1H NMR, 13C NMR, and HRMS techniques, providing detailed structural insights. The in vitro antibacterial assessments were conducted via the agar diffusion method, revealing that compounds 3a, 3d, 3g, and 3j exhibited potent activity against both gram-positive (B. subtilis, MRSA) and gram-negative (E. coli) bacterial strains, providing objective data on their effectiveness. Furthermore, compound 3j, which featured bromine substitution at C5 of N-allyl isatin, displayed significant inhibition zones of 27 mm and 20 mm against E. coli and VRE, respectively, surpassing the activity of ciprofloxacin used as a standard drug molecule, thereby providing specific results. The molecular docking studies against E. coli Peptide Deformylase complex further confirmed the antibacterial potential of the synthesized compounds, adding a scientific basis for their efficacy. Additionally, in silico ADME predictions indicated favourable oral bioavailability, highlighting the promise of N-Boc substituted isatin Schiff bases as potential candidates for the development of novel antibacterial agents, thus contributing to the objective evaluation of their pharmacokinetic properties. Consequently, our studies demonstrated that these compounds not only possess significant antibacterial activity but also show promising pharmacokinetic properties, positioning them as strong candidates for the development of new antibacterial agents.

Synthesis and characterization of indazole derived Schiff base ligands and their metal complexes: Biological and computational studies

Indazoles represent one of the most important heterocycles in drug molecules. Therefore, in the pursuit of potent biological agents, a series of ligands (HL1-HL4) and their corresponding transition metal complexes [M(L1-L4)2(H2O)2] were synthesized by the condensation reaction of 6-aminoindazole with various derivatives of salicylaldehyde. Further, the compounds underwent characterization through several physicochemical (TGA, powder XRD, SEM, EDAX) and spectroscopic techniques (FT-IR, UV–Vis, NMR, mass spectrometry, ESR). These techniques suggested hexacoordinated stereochemistry of the metal complexes, where ligands chelate via oxygen atom of phenolic ring, azomethine nitrogen and oxygen atom of water molecules in 1:2 (M:L) molar ratio. The thermal stability of the complexes was demonstrated by thermal analysis revealing three step decompositions leaving behind metal oxide as an end residue. The surface morphology of the ligands was distinct from metal complexes as revealed by SEM analysis, while mapping images demonstrated the simultaneously existence of the elements. While, to ascertain the nature of the obtained compounds (crystalline or amorphous), powder X-ray investigation was conducted by utilizing a wavelength of 1.54 Å. The compound’s antioxidant potential was assessed through DPPH assays and anti-inflammatory activity was evaluated using BSA denaturation inhibition assay, while their antimicrobial potential was evaluated against six microbial strains (E. coli, S. aureus, P. aeruginosa, B. subtilis, C. albicans, A. niger) by serial dilution approach. The performed biological evaluations revealed that the complexes are more efficient in controlling infectious ailment in comparison of ligands. HL2 (2) and its Cu(II), Zn(II) complexes (11, 12) exhibited potent antimicrobial activity (MIC value: 0.0047, 0.0048 µmol/mL against B. subtilis) and potent anti-inflammatory efficacy (IC50 value: 6.7 ± 0.044, 6.9 ± 0.036 µM). All the complexes exhibited potent antioxidant activity and their is enhancement in the activity of Schiff base ligands upon complexation, complex (19) demonstrated the greatest activity with IC50 value 2.1 ± 0.059. Additionally, the ADMET score provided a robust indication of the compounds’ drug-like behaviour. Furthermore, the biological effectiveness of the highly microbial potent ligand HL2 (2) and its complexes (9–12) was demonstrated through computational studies. The binding studies exposed that complexes (11, 12) exhibited lowest binding energy at −7.8, −7.9 kcal/mol. While, DFT study emphasized that complex (12) exhibits the highest electrophilicity index value (6.359), suggesting its affinity for binding with biological molecules and also revealed that complexes exhibit greater potency compared to the ligands and could potentially be utilized as drugs for combatting pathogen-induced malformations.

Intramolecular Halogen Bonding: Enantiomer Induced by 'rhombic-shape' Intramolecular Halogen Bonding

Programmable supramolecular materials assembled from chiral components are receiving increasing attention. Herein, we report a self-assembled racemic based on a halogenated Schiff base complex, [Cu3L2Cl2(H2O)] (L = N, N'-bis (3-Bromosalicylidene) ethylene-1,3-diaminopropane). Structural analysis reveals that the disappearance of molecular symmetry is closely related to the unique intramolecular 'rhombic-shape' halogen bonding of the compound. To the best of our knowledge, this is the first example of 'rhombic-shape' halogen bonding within a single molecule. To gain deeper mechanistic insight into the formation of this peculiar structure, we performed a series of structural analyses and theoretical calculations on the reported compound. The results suggest that the 'rhombic-shape' halogen bonding structure formed among the four Br atoms is asymmetric. This asymmetry structural feature further affects the molecular symmetry and serves as the primary factor inducing the special chirality in the molecule.

A comparative study of two thienopyrimidine Schiff base probes for sequential monitoring of Ga3+ and Pd2.

Two Schiff base probes (S1 and S2) were prepared and synthesized by incorporating thienopyrimidine into salicylaldehyde or 3-ethoxysalicylaldehyde individually, with the aim of detecting Ga3+ and Pd2+ sequentially. Upon chelation with Ga3+, S1 and S2 exhibited fluorescence enhancement in DMSO/H2O buffer. Both S1-Ga3+ and S2-Ga3+ were quenched by Pd2+. The limit of detection for S1 in response to Ga3+ and Pd2+ was 2.86 × 10-7 and 4.4 × 10-9M, respectively. For S2, the limit of detection for Ga3+ and Pd2+ was 4.15 × 10-8 and 3.0 × 10-9M, respectively. Furthermore, the complexation ratios of both S1 and S2 with Ga3+ and Pd2+ were determined to be 1:2 through Job's plots, ESI-MS analysis, and theoretical calculations. Two molecular logic gates were constructed, leveraging the response behaviors of S1 and S2. Moreover, the potential utility of S1 and S2 for monitoring Ga3+ and Pd2+ in domestic water was verified.

A novel organoselenium-based Schiff base for selective separation of copper and zinc from food samples using ultrasonic-assisted solidified floating organic drop microextraction strategy

Herein, we document the development of a novel organoselenium-based Schiff base, 2-((4-((2-hydroxy-4-nitrobenzylidene)amino)phenyl)selanyl)-N-phenylacetamide (HOASe), to selectively separate zinc and copper from food samples. To the best of our knowledge, OSe compound has never been used in microextraction procedures before, until today. HOASe was synthesized from aniline by a simple four-step procedure. The structure of HOASe was elucidated by various spectroscopic techniques (e.g., IR, MS, 1H- and 13C NMR). After that, HOASe was used to extract Cu2+ and Zn2+ by ultrasonic-assisted dispersive liquid-liquid microextraction based on the solidification of floating organic drop (UA-DLLME-SFOD) combined with flame atomic absorption spectrometry. Important experimental parameters including amount of the extraction solvent, initial pH, amount of HOASe, ultrasonication time, centrifugation, and salt addition, were studied and optimized to offer quantitative separation of the analytes. The detection limits and the linear ranges for Cu2+ and Zn2+ were 1.9, 8.0 – 400.0, and 2.4, 6 – 150 μg L-1, respectively. The method's greenness and applicability were assessed using the Analytical GREEnness metric methodology and the Blue Applicability Grade Index, respectively. Finaly, this approach was used for quantification of Cu2+ and Zn2+ in food samples and, therefore, can be further developed for food safety and quality control programs.

Novel Co(II), Cu(II) and Fe(II) Pentadentate Schiff base complexes: Synthesis, characterization, antimicrobial, antioxidant, and molecular docking studies

The compound H2L, which is a ligand with five coordinating atoms, consisting of three nitrogen atoms and two sulfur atoms (N3S2), was reacted with Fe(OAc)2, Cu(OAc)2.H2O, and Co(OAc)2·4H2O to form the corresponding metal complexes ([FeL], [CuL], [CoL]). Many techniques, including NMR (for ligand), FT-IR, UV–Vis, elemental analysis, and molar conductivity, were used to characterize the synthesized compounds. According to the spectrum of data, complex molecule structures have a distorted triangular bipyramidal geometry with five coordination locations. The compounds that exhibit non-electrolyte behavior in solution do not possess any conductivity features. Evaluation was performed to determine the antioxidant activity of the synthesized compounds in comparison to the stable free radical DPPH. The ligand and its metal complexes were evaluated for antibacterial activity against several Gram-positive and Gram-negative bacteria, as well as a yeast strain. In comparison to the common antibiotic Amoxycillin/Clavulanic Acid (AMC-30), the Schiff base ligand (H2L) and its Cu(II) metal complex showed noticeably larger inhibitory zones against S. aureus. All the compounds showed a high negative binding affinity for S. aureus amino acid molecules when they were docked. The results indicated that the metal complexes, particularly the cobalt complex, exhibited a higher affinity for binding compared to the free ligand.