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The ultrafast proton transfer and the following dynamics for aromatic Schiff bases N,N′-bis(salicylidene)ethylenediamine (salen) and N,N′-bis(salicylidene)-1,4-butylenediamine (salbn) were investigated with experimental and theoretical methods. A dual emission property with a large Stokes shift in salen and salbn indicates that excited state intramolecular proton transfer occurs with photoexcitation. An efficient single proton transfer was confirmed within 200 fs for both molecules. Subsequently, a fast twisted motion of the keto moiety carries cis-keto to a relaxed stable geometry in the S1 state. Following the twisted motion, the phenol ring at keto moiety further rotates to a conical intersection with the ground state and a cis–trans isomerization occurs. The isomerization rate is high, which dominates the competition with the radiative transition, resulting in weak emission intensity. It is confirmed that the length of alkyl chain affects the direction of phenol ring twisting and rotation during the whole subsequent relaxation of excited cis-keto tautomer. Compared with polar solvent acetonitrile, the barrier of isomerization is higher and the hydrogen bond on keto moiety is stronger in nonpolar solvent toluene. It makes fluorescence radiation channels competing with isomerism more likely to occur, contributing to the observed difference of enol/keto emission ratios of salen and salbn in toluene and acetonitrile. [ABSTRACT FROM AUTHOR]

To develop a green nanomaterial for specialty applications, spherical nanocellulose (SNC) was functionalized to a semicarbazone-Schiff base via a polymer analogous reaction. Firstly, SNC was synthesized from cellulose extracted from huge forest biomass, pine needles (PNs). The glucopyranose ring of SNC was oxidatively cleaved at C2-C3 to form SNC-dialdehyde (SNC-DA) by periodate oxidation. Both the aldehydic groups generated were reacted with semicarbazide to form a semicarbazone-Schiff base, referred to as functional spherical nanocellulose (FSNC). All the materials synthesized were characterized by FTIR, FESEM, EDS, TEM, and XRD studies. The FSNC was evaluated as an adsorbent for [Hg.sup.2+] ions. The adsorption adhered to pseudo-second order kinetics and Langmuir adsorption isotherm having a maximum adsorption capacity/Lungmuir adsorption capacity of 172.412 mg/g at 60 min. The selectivity of FSNC for [Hg.sup.2+] ions was confirmed from its appreciable removal (82%) from solution in tap water and 70% with other metal ions. FSNC exhibited bifunctional nature as it possesses antimicrobial activity against bacteria, that is, Gram (+) (Bacillus aereus) and Gram (--) (Escherichia coll and Salmonella typhi), and a fungus Byssochlamys fiilva. FSNC showed good recyclability up to eight sorption-desorption cycles. Thus, we have valorized biomass into an eco-friendly and low-cost bifunctional material as an adsorbent for [Hg.sup.2+] ions cum antimicrobial agent. Highlights * Spherical nanocellulose (SNC) prepared via acidic hydrolysis from pine needles * SNC functionalized to semicarbazone-based bifunctional Schiff base * The Schiff base is a rapid and efficient [Hg.sup.2+] ions adsorbent * The Schiff base has good antimicrobial activities against Gram (-) bacteria * Biowaste-based adsorbent has the potential to sustain the bio-circular economy KEYWORDS antimicrobial, pine needles, Schiff base, semicarbazone, spherical nanocellulose, 1 | INTRODUCTION The sustainability development goals have a deep link with the failing water quality and low availability of drinkable water across the world. (1) Among different pollutants, dyes [...]

In this paper, three different Zn(II) complexes with (E)-2-(2-(1-(6-bromopyridin-2-yl)ethylidene)hydrazinyl)-N,N,N-trimethyl-2-oxoethan-1-aminium chloride (HLCl) have been synthesized and characterized by single crystal X-ray diffraction, elemental analysis, IR and NMR spectroscopy. All complexes are mononuclear, with the ligand (L) coordinated in a deprotonated formally neutral zwitterionic form via NNO donor set atoms. Complex 1 forms an octahedral geometry with the composition [ZnL2](BF4)2, while complexes 2 [ZnL(NCO)2] and 3 [ZnL(N3)2] form penta-coordinated geometry. Density functional theory (DFT) calculations were performed to enhance our understanding of the structures of the synthesized complexes and the cytotoxic activity of the complexes was tested against five human cancer cell lines (HeLa, A549, MDA-MB-231, K562, LS 174T) and normal human fibroblasts MRC-5. Additionally, antibacterial and antifungal activity of these complexes was tested against a panel of Gram-negative and Gram-positive bacteria, two fungal strains, and a yeast strain. It is noteworthy that all three complexes show selective antifungal activity comparable to that of amphotericin B. Molecular docking analysis predicted that geranylgeranyl pyrophosphate synthase, an enzyme essential for sterol biosynthesis, is the most likely target for inhibition by the tested complexes. [ABSTRACT FROM AUTHOR]

Eugenol, the major constituent of clove oil, has been explored as an essential natural ingredient for ages owing to its versatile pharmacological properties. However, to date, the coordination chemistry of eugenol derivatives has not been much explored. In the present work, an eugenol-based Schiff base ligand (HL) was synthesized and structurally confirmed through ESI-MS, NMR, and FT-IR spectroscopy studies. Consequently, the N,O-donor chelating ligand HL was coordinated with Cd2+, in the presence of bridging pseudohalides (thiocyanate, SCN−, and dicyanamide, N(CN)2−) to synthesize two luminescent coordination polymers (CPs 1 and 2): [Cd2(L)2(X)2]n (where HL = 4-allyl-2-(((2-(benzylamino)ethyl) imino)methyl)-6-methoxyphenol and Xs are bridging pseudohalides, i.e., SCN− and N(CN)2−) on a Cd-eugenol scaffold. The CPs depicted structural diversity, bulk-phase purity, thermal stability, and the presence of interlayer supramolecular C–H⋯π interactions together with C–H⋯S (for CP 1) and C–H⋯N (for CP 2) interactions. The CPs further exemplified themselves as selective and sensitive 'turn-off' probes towards trinitrophenol (TNP) (quenching efficiency: 82.02% and 83.86% for 1 and 2) among a pool of hazardous nitroaromatic compounds (NACs). Accordingly, 1 and 2 exhibited an ultralow limit of detection (LOD) of 0.29 and 0.15 μM, with high quenching constants (KSV) of 5.91 × 104 and 17.60 × 104 M−1, respectively. In addition, TNP sensing events were evidenced to be recyclable and exhibited fast response (∼31 s, 1, and ∼40 s, 2), which increased its real-world viability. Vapor phase TNP sensing was also accomplished upon drop-casted CP films. Experimental investigations and theoretical DFT study confirmed the cooperative occurrence of RET-IFE-PET-collisional quenching and non-covalent π⋯π stacking as key factors involved in the TNP sensing performance. The competency of 1 and 2 in the detection of TNP from several complex environmental matrices (CEMs), viz. matchstick powder, river and sewage water, and soil specimens, was also established with good recovery (∼66–86% and ∼68–93% for 1 and 2, respectively) and high KSV values (3.90–11.39 × 104 and 6.17–18.79 × 104 M−1 for 1 and 2, respectively). [ABSTRACT FROM AUTHOR]

New graphene Schiff base iron nanocomplexes (S-792-Fe, S-550-Fe, and S-590-Fe) were designed and fabricated based on investigations of reactions mechanisms of AP pyrolysis, structural analysis of new materials and simulation results of quantum mechanics to deal with the long-standing contradiction between safety and performance for composite propellent combustion catalyst. By taking traditional catalyst Catocene as the benchmark, the S-550-Fe nanocomplexes exhibited competitive catalytic performances, much better anti-migration properties and significantly reduced impact and electrostatic sensitivities. After adding S-550-Fe, the burning rate of propellant enhanced from 13.87 to 19.77 mm s−1 at 15 MPa, and the impact and electrostatic sensitivities are improved to 50.2 cm and 172.12 mJ, respectively. The excellent catalytic performance of S-550-Fe is closely related to its molecular structure, which is manifested by an increase in charge density and a decrease in NH 3 oxidation energy barriers. The promotion effects of S-550-Fe on desorption and oxidation of NH 3 from the surface of AP is conducive to the rapid and complete pyrolysis of AP, which is reflected in the improvement of combustion rate and temperature gradient. The theory-driven design mode of this work may provide new pathways to tune combustion behaviors of composite propellants from the view of molecular-level insights. Effects and mechanisms of S-550-Fe on combustion and safety of AP-HTPB propellant were disclosed. [Display omitted] • Graphen Schiff base Fe nanocomplexes were first investigated in AP-HTPB propellant. • S-550-Fe is conducive to the combustion and safety performance of AP-HTPB propellant. • The structure-activity relationship of S-550-Fe at the molecular level was explored. • The influence of catalysts on NH 3 oxidation process was revealed. [ABSTRACT FROM AUTHOR]

A modified carbon paste sensor based on N,N′-(((ethane-1,2-diylbis(oxy))bis(2,1-phenylene))bis(methanylylidene))bis(pyridine-2-amine; BPA Schiff base as Cr(III) selective carrier was fabricated and studied in this work. The proposed sensor homogenization and mechanism of action was studied by infra-red (IR) and scanning electron microscope (SEM) with energy dispersive X-ray (EDX) tools. The sensor covered 1.0 × 10−7–1.0 × 10–1 mol L−1 linear range and a detection limit of 7.22 × 10–8 mol L−1 for Cr(III) with 20.17 ± 0.13 mV decade−1 Nernstian slope. 5 s was the response time of the prepared sensor and it was reproducible and stable for 3 months. The working pH range was 3.3–6.0 and it also works well to determine Cr(III) ion in presence of water miscible solvents up to 12.5% content of the methanol and 17.5% of ethanol. The electrode's selectivity was studied using separate and mixed solution methods for selectivity coefficients determination and the sensor showed good selectivity relative to a variety of metal ions (selectivity coefficients = 1.01 × 10−5–8.57 × 10−3). In addition, the practical analysis value of the sensor was demonstrated by measurement of Cr(III) quantitatively in mineral water, supplement and also as an indicator electrode in Cr(III) against EDTA potentiometric titration with good reproducibility (RSDs of 0.91–2.15%). [ABSTRACT FROM AUTHOR]

Gastric ulcers accompanied by acute or chronic bleeding represent a significant risk of fatality. However, the development of effective strategies for achieving rapid hemostasis and wound healing in gastric ulcer bleeding represents a formidable challenge. To address this challenge, thrombin‐derived C‐terminal peptide (TCP‐25) is employed as a targeted agent, and it is incorporated into two novel injectable and biocompatible carboxymethyl chitosan (CMCs) hydrogels via Schiff's base reaction. The TCP‐25 peptide hydrogels display optimal adaptability within the distinctive gastrointestinal microenvironment, demonstrating a balance of acid resistance and degradation, along with controlled release and bioactivity, and good bio‐adhesive properties. Both in vitro and in vivo reveal that the hydrogel achieves rapid hemostasis. In an ethanol‐induced gastric ulcer model in rats, it demonstrates that the hydrogel effectively inhibits gastric ulcer bleeding by 92% within 24‐h, exhibiting efficacy that surpasses that of omeprazole medicine, a commonly used clinical treatment. This enhanced performance is attributed to the synergistic effects of the CMCs hydrogel and TCP‐25 peptide in effectively achieving hemostasis, inhibiting bacterial growth, and promoting gastric wound healing in acute or chronic bleeding gastric ulcers. Consequently, the present work offers promising clinical applications for rapid hemostasis and wound healing in gastric ulcers. [ABSTRACT FROM AUTHOR]

Metal-based drugs are finding new medical applications, particularly in antibacterial therapies. Compounds such as Prontosil and ciprofloxacin, as well as its derivatives such as beta-lactam drugs, aminoglycosides, vancomycin, fosfomycin, as well as tetracyclines, play critical roles in the prevention of bacterial and fungal infections. The increasing prevalence of microbial resistance is prompting the use of metal complexes to tackle fungal and bacterial strains. Mercury-based complexes, which are known for their unusual characteristics and reactivity, have received a lot of interest in the field of medicine recently. Additionally, Schiff base complexes are widely used as antifungal, antibacterial, and anticancer drugs, as well as in dye manufacturing. This article discusses current advances in the use of mercury compounds for combating fungus and bacteria, offering information on their efficacy and future applications. [ABSTRACT FROM AUTHOR]

We synthesized a sublimable molecular spin crossover Fe(II) complex based on the Schiff base tridentate ligand qsal-NEt2 (5-diethylamino-2-((quinolin-8-ylimino)methyl)phenol). The compound undergoes a transition in temperature with thermally induced excited spin state-trapping (TIESST) for high-temperature sweep rates, which can be suppressed by reducing the sweep rate. The X-ray absorption spectroscopy (XAS) studies on the microcrystalline powder confirm the TIESST effect. The molecules are deposited under ultra-high vacuum on a graphene/SiO2 substrate as a submonolayer. Investigation of the submonolayer by XAS reveals the molecular integrity and shows a spin crossover for the whole temperature range from 350 to 4 K, with residual HS species at low temperature and no TIESST effect. DFT calculations suggest a distribution of energetically similar adsorption configurations on graphene, i.e., with smooth crossover behaviour and the absence of TIESST, consistent with very weak intermolecular interactions and the absence of large molecular islands within the submonolayer. [ABSTRACT FROM AUTHOR]

The synthesis of eleven new nickel Schiff base complexes each bearing four pendant groups is reported. The structures of the complexes differ in the identity of the pendant groups and/or diamine moiety. All complexes were characterised by microanalysis, Nuclear Magnetic Resonance (NMR) spectroscopy and Electrospray Ionisation Mass Spectrometry (ESI-MS), while the solid-state structures of two of the molecules were also determined using X-ray crystallographic methods. The DNA binding properties of the nickel complexes with double stranded DNA and a range of G-quadruplex DNA structures was explored using different spectroscopic methods as well as computational techniques. Results from ESI-MS experiments and Fluorescent Indicator Displacement (FID) assays were consistent with each other and indicated that varying the diamine moiety had less influence on DNA affinity than changing the pendant groups. These conclusions were also generally supported by results obtained from UV melting experiments and Fluorescence Resonance Energy Transfer (FRET) assays. The cytotoxicity of selected examples of the new complexes, and close analogues reported recently, towards V79 Chinese hamster lung cancer cells and THP-1 human leukemia cells was measured. All were found to display modest cytotoxicity, with flow cytometry experiments suggesting an apoptotic pathway was the most likely mechanism of cell death. [ABSTRACT FROM AUTHOR]

Biobased hydrogels have been widely used in drug delivery, tissue engineering and biosensors due to their abundance, non-toxicity and biocompatibility. However, constructing fully biobased hydrogels with good mechanical performance still remains a challenge. Herein, a double network (DN) hydrogel consisting of oxidized hydroxypropyl guar gum (OHPG) and gelatin (Gel) was fabricated via Schiff base reaction. The Gel-OHPG hydrogel had an elongation at break of 497%, a tensile stress of 0.44 MPa and a compressive stress of 25.91 MPa. Then, the mechanical properties of the hydrogel were further enhanced through immersing it in an ammonium sulfate (AMS) solution due to the Hofmeister effect. Its elongation could reach 629% and the corresponding tensile toughness and compressive stress were 3.86 MPa and 59.55 MPa, respectively. The conductivity of the hydrogel was 0.86 S m−1. Furthermore, the Gel-OHPG hydrogel was fabricated as a flexible sensor, and it could accurately monitor human joint motions such as fingers, wrists, knees, elbows, throat and neck. Henceforth, the Gel-OHPG hydrogel prepared using fully natural polymers has promising potential in flexible sensors and tissue engineering. [ABSTRACT FROM AUTHOR]

Two halogenated Schiff bases namely, (E)-1-(((2,6-dichlorophenyl)imino)methyl)naphthalen-2-ol (L1) and (E)-1-(((4-bromo-2,6-dichlorophenyl)imino)methyl)naphthalen-2-ol (L2) were synthesized and reacted with copper(II) nitrate trihydrate in ethanol to give Cu(L1)2 (1) and Cu(L2)2 (2). All the ligands and complexes were successfully characterized using FT-IR, UV-Vis, 1H & 13C-NMR as well as mass spectra and the purity was ascertained by elemental analysis. Electron paramagnetic resonance (EPR) was used to confirm the paramagnetic nature of 1 and 2. Furthermore, the single X-ray crystal structures of 1 and 2 were determined, confirming the formation of mononuclear species in which the Cu(II) center was bonded to two bidentate Schiff bases (L1 or L2) adopting a slightly distorted square planar geometry. Density Function Theory studies revealed that, complex 2 with lowest energy band gap (ΔE) of 2.49 eV is the most reactive among the compounds. α-Amylase and α-glucosidase assays were used to evaluate the antidiabetics potential of the compounds. Complexes 1 and 2 displayed very promising antidiabetic activities with IC50 values of 148.126 mM and 107.786 mM for α-amylase assay while it was 171.559 mM for acarbose (reference drug). The antioxidant potential of the compounds was investigated using nitric oxide (NO), ferric reducing ability power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. The compounds showed moderate to good antioxidant activities with 1 and 2 having IC50 values of 100.044 mM and 247.463 mM for NO scavenging assay, which relatively surpass Vanillin with IC50 value of 466.626 mM. All the compounds showed poor to moderate results against Escherichia coli, Staphylococcus aureus, Bacillus substilis, and Pseudomonas aeruginosa. However, none of them were active against Klebsiella pneumoniae. Generally, 1 and 2 displayed better antidiabetes, antioxidant, and antibacterial potential than L1 and L2. Predicted physicochemical and pharmacokinetic properties of all the compounds showed minimal violation of Lipinski's Ro5. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Porous organic polymers (POPs) have attracted great attention in past decades. Although diverse functional POPs have been developed, multistimuli‐responsive POPs with excellent aggregate‐state luminescence together with good chiroptical properties have rarely been reported. Herein, two pairs of Salen‐type enantiomeric POPs with multistimuli‐responsive luminescence and chiral features were designed and synthesized by facile polycondensation reactions between polyfunctional aggregation‐induced emission luminogen (AIEgen)‐containing salicylaldehyde derivatives and chiral diamines. With Salen units in polymer backbones as tetradentate ligands, a series of POP‐metal complexes were further prepared. The obtained POPs and metal complexes show good porosity, high thermal stability, and obvious circular dichroism signals. Moreover, benefiting from the coexistence of AIEgen and Salen units in polymer structures, these POPs exhibit excellent luminescence performance in aggregate states and tunable fluorescence behaviors in response to external stimuli of Zn2+ ion, mechanical forces, organic solvent, and acids. Due to the dynamic feature of Schiff base C=N bonds, the present POPs can efficiently undergo hydrolysis reactions under strong acidic conditions to reproduce the AIEgen‐ containing monomers, and such an acid‐induced degradation process can be directly visualized and dynamically monitored via fluorescence variation. These properties collectively make the POPs candidate materials for applications in heterogeneous asymmetric catalysis, fluorescence sensing, biomedicine, etc. [ABSTRACT FROM AUTHOR]

Three novel Schiff base polymers were synthesized by using the Schiff base monomer obtained using aldehyde containing boric acid and amines containing hydroxyl groups as the starting materials. The polymers were synthesized at the same temperature and using the same amount of oxidizing agent by the oxidative polycondensation method. The characterization of all polymers and monomers was achieved by using Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible spectroscopy (UV–vis), nuclear magnetic resonance spectroscopy (1H-NMR), liquid chromatography-mass spectrometry (LC–MS), gel permeation chromatography (GPC) and scanning electron microscopy (SEM). The thermal stability of these compounds was studied by employing thermogravimetric analysis (TGA), and thermodynamics parameters such as activation energy (Ea), enthalpy (∆H), entropy (∆S), and Gibbs free energy(∆G) for the decomposition process were calculated using the Flynn–Wall–Ozawa method. [ABSTRACT FROM AUTHOR]

In this report, we have synthesized two new NCS pincer ligands by the Schiff base reaction of 3‐((phenylthio)methoxy)benzaldehyde (P) with alkyl amines (tbutylamine (L1) and 1‐adamantylamine (L2)). The palladium pincer complexes (tbutylamine=C1 and 1‐adamantylamine=C2) of these ligands were synthesized by their reaction with PdCl2(CH3CN)2 precursor. The newly synthesized ligands and complexes were characterized using various analytical and spectroscopic techniques such as 1H, 13C{1H} Nuclear Magnetic Resonance (NMR), Ultraviolet–visible (UV‐Visible), Fourier Transform Infrared (FTIR) Spectroscopy, and High‐Resolution Mass Spectrometry (HRMS). The structure of the ligand and its coordination mode with palladium precursor were studied with the help of single‐crystal X‐ray diffraction. The complexes showed distorted square planar geometry around the palladium center. The palladium pincer complexes were used as catalysts for the regioselective cross‐dehydrogenative alkenation of 2‐arylthiophene derivatives. The complex C2, where sterically bulky adamantyl ligand is part of the side arm showed a higher yield of alkenation reaction. Only 2.5 mol% catalyst loading was sufficient to achieve 74–95 % yields of desired products with excellent functional group tolerance under mild reaction conditions. The poisoning experiments (PPh3 and Hg) showed the homogeneous nature of the catalytic process. The plausible mechanism of the reaction was proposed based on the control experiments and time‐dependent HRMS studies. [ABSTRACT FROM AUTHOR]

The development of efficient synthetic strategies for the preparation of tetrasubstituted N−H pyrrole derivatives, especially in an environmentally benign fashion is important yet challenging. Herein, we report a copper(II)‐catalyzed tandem reaction involving 1,3‐dipolar cycloaddition of α,β‐ynones and glycine iminoesters, followed by copper(II)‐promoted oxidative (air) dehydrogenative aromatization, allowing de novo access to tetrasubstituted N−H pyrroles in up to 81 % yield under green reaction conditions. A possible reaction pathway is tentatively proposed. Finally, fully substituted pyrroles are available by N‐alkylation, and a preliminary phase‐transfer catalytic asymmetric N‐alkylation was also studied to give an axially chiral pyrrole. [ABSTRACT FROM AUTHOR]

This study investigates organotin (IV) complexes derived from the recently synthesized quinazoline Schiff base ligand (L). The research involves synthesizing and characterizing these complexes, including elemental analysis, UV–visible, FT‐IR, mass spectra, and conductometric measurements. Advanced studies such as density functional theory (DFT) are employed to gain insights into the stable electronic configuration. Specifically, the study explores the proposed geometry, revealing a distorted octahedral structure for the complexes. The findings contribute as critical molecular characteristics of these newly synthesized complexes, paving the way for potential applications in diverse fields, including medicinal chemistry. Through an investigation into the antimicrobial properties, the efficacy of the synthesized compounds was assessed against a diverse range of bacterial and fungal strains. Remarkably, the complexes demonstrated significant antimicrobial activities, showing potential applications in combating various microbial infections. In an extended exploration of their medical utility, the compounds were examined for their antibiotic properties against Helicobacter pylori. The Schiff base and its metal complexes emerged as promising antibiotics with notable efficacy against H. pylori, suggesting their potential in addressing infections associated with this bacterium. Furthermore, the antitumor potential of the synthesized complexes was investigated, focusing on their impact on MCF‐7 (Breast carcinoma) cells. The organotin (IV) Schiff base complexes in this research showed remarkable efficacy, evidenced by their notably low IC50 values (9, 10, 11 μg/mL) in comparison with cisplatin. In addition to their potent antitumor effects, these complexes exhibited reduced cytotoxicity toward normal cells (VERO cells) compared with cisplatin. The investigation extends to molecular docking, where this approach aims to elucidate their interactions with specific protein structures, including (2JFZ, 1SC7, and 6W41). The primary objective is to clarify the potential properties of these compounds, focusing on their antibiotic efficacy, anti‐H. pylori activity, antitumor potential, and anti‐COVID‐19 properties. [ABSTRACT FROM AUTHOR]

We synthesized a sublimable molecular spin crossover Fe(II) complex based on the Schiff base tridentate ligand qsal-NEt2 (5-diethylamino-2-((quinolin-8-ylimino)methyl)phenol). The compound undergoes a transition in temperature with thermally induced excited spin state-trapping (TIESST) for high-temperature sweep rates, which can be suppressed by reducing the sweep rate. The X-ray absorption spectroscopy (XAS) studies on the microcrystalline powder confirm the TIESST effect. The molecules are deposited under ultra-high vacuum on a graphene/SiO2 substrate as a submonolayer. Investigation of the submonolayer by XAS reveals the molecular integrity and shows a spin crossover for the whole temperature range from 350 to 4 K, with residual HS species at low temperature and no TIESST effect. DFT calculations suggest a distribution of energetically similar adsorption configurations on graphene, i.e., with smooth crossover behaviour and the absence of TIESST, consistent with very weak intermolecular interactions and the absence of large molecular islands within the submonolayer. [ABSTRACT FROM AUTHOR]

Mixed ligand complexes of manganese(II), cobalt(II), copper(II), and cadmium(II)with an innovative Schiff base ligand denoted as (L1), 4-(2-((1E,2E)-1-(2-(p-tolyl)hydrazineylidene)propan-2-ylidene)hydrazineyl), served as the principal ligand, while glycine (L2) was employed as secondary ligand were successfully effectively characterized through a comprehensive set of analyses, including Elemental analysis, UV–Visible, FT-IR, Mass spectra, and conductometric measurements. Density functional theory (DFT) computations were executed to discern the enduring electronic arrangement, the energy gap, dipole moment and chemical hardness of the hybrid ligand assemblies. The proposed geometry for the complexes is a distorted octahedral structure. The antimicrobial efficacy of these compounds was assessed against a range of bacterial and fungal strains. Notably, these complexes exhibited promising antimicrobial activities, with the cadmium (II) complex demonstrating superior efficacy towards all tested organisms. These compounds were also examined for their antibiotic properties against H. pylori to explore their broader medical potential. The Schiff base ligand and its corresponding metal complexes displayed substantial potential as an antibiotic against H. pylori. Additionally, the antitumor potential of the synthesized complexes was assessed against MCF-7 (Breast carcinoma) cells—the Cu (II) complex demonstrated superior activity with the lowest IC50 value compared to cisplatin. Moreover, it exhibited reduced cytotoxicity towards normal cells (VERO cells) compared to cisplatin, establishing it as the most potent compound in the study. Furthermore, molecular docking was explored of the Schiff base ligand and its corresponding cadmium(II) complex. The analysis of the docking study yielded valuable structural insights that can be effectively utilized in conducting inhibition studies for example against COVID-19. This comprehensive study highlights these synthesized compounds' multifaceted applications and promising bioactive properties. [ABSTRACT FROM AUTHOR]

Treatment of [Co(N2)(tBuPNP)] (tBuPNP = anion of 2,5-bis(di-tert-butylphosphinomethyl)pyrrole) with one equivalent of an aryl azide generates the four-coordinate imido complexes [Co(NAr)(tBuPNP)] (Ar = mesityl, phenyl, or 4-tBu-phenyl). X-ray crystallographic analysis of the compounds shows an unusual square-planar geometry about cobalt with nearly linear imido units. In the presence of the hydrogen atom donor, TEMPOH, [Co(NPh)(tBuPNP)] undergoes addition of the H atom to the imido nitrogen to generate the corresponding amido complex, [Co(NHPh)(tBuPNP)], whose structure and composition were verified by independent synthesis. Despite the observation of H atom transfer reactivity with TEMPOH, the imido complexes do not show catalytic activity for C–H amination or aziridination for several substrates examined. In the case of [Co(NPh)(tBuPNP)], addition of excess azide produced the tetrazido complex, [Co(N4Ph2)(tBuPNP)], whose bond metrics were most consistent with an anionic Ph2N4 ligand. Density Functional Theory (DFT) investigations of the imido and tetrazido species suggest that they adopt a ground state best described as possessing a low-spin cobalt(II) ion ferromagnetically coupled to an iminyl radical. [ABSTRACT FROM AUTHOR]

We synthesised a sequence of structurally related copper(II) complexes of Schiff base ligands, 2-[(2-benzylamino-ethylimino)-methyl]-phenol [L1(H)], 2-[(2-benzylamino-ethylimino)-methyl]-4-methyl-phenol [L2(H)], and 2-[(2-benzylamino-ethylimino)-methyl]-4-bromo-phenol [L3(H)]. The complexes were characterized by ATR, UV-vis, EPR, ESI-MS, single crystal XRD, and elemental analyses. Based on the crystal structure, the ligand was coordinated to the copper(II) centre in a tridentate mode through phenolate(oxygen), imine nitrogen and amine nitrogen in an NNO fashion and the azide moiety served as an auxiliary ligand. Furthermore, we have investigated the antimicrobial activities of copper(II) complexes against clinically relevant fungal strains, including Candida albicans, Candida glabrata, and Candida tropicalis, as well as bacteria such as Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA), representing Gram-negative and Gram-positive pathogenic strains. Comparing the activity of complex 2 (128–512 μg mL−1) to complex 3 (64–128 μg mL−1), the latter demonstrated more potent effectiveness against all of the tested fungal strains. The activity of the complexes against MRSA reveals the inhibitory concentrations of 1024 μg mL−1 for 1, 128 μg mL−1 for 2, and 256 μg mL−1 for 3. It is worth mentioning that, at their minimum inhibitory concentrations (MICs), the complexes are not toxic to Galleria mellonella. Furthermore, the spot and broth microdilution assay results were in good agreement with the actual metabolic viability of bacterial and fungal strains, in which the complexes were active while having no effect on the metabolite resazurin. Additionally, in silico studies have been employed to elucidate both non-bonding interactions and the mode of action across protein sequences of experimentally studied microbes. The performance of complexes closely mirrored the reactivity order determined in in vitro studies. The impeding properties of complexes can be due to the dysfunctioning of virulent genes and signalling proteins and also affect the activities of transferase and transcriptase proteins. Overall, the complexes are promising candidates for antimicrobial drug development. We anticipate utilising these molecules for clinical purposes. [ABSTRACT FROM AUTHOR]

A series of non-innocent halogen substituted Schiff base vanadium catecholates were added with different electron donating and withdrawing substituents on the catecholates to investigate the electronic effects on the properties of this class of compounds. We hypothesized that the electronic changes would be reflected in their redox properties and stabilities, which should lead to differences in their biological properties. Using UV-spectroscopy, we measured their hydrolytic stability, and using electrochemistry, we characterized their redox properties. Adding one substituent on the catecholate group on the complexes changed the redox potentials of the complexes; however, less impact on the hydrolytic stability was observed. We discovered that hydrolytic stability was crucial to the anti-proliferative effects on glioblastoma cells, and most of these compounds had effects similar to vanadates regardless of their different redox properties. Hence, we could not determine the importance of changing the electronic properties and redox potential on the anti-proliferative effects of mono-substituted catecholates. However, the studies did show that the pKa of the substituted catecholate showed a linear correlation with the redox potential of the non-innocent Schiff base vanadium complexes, which will be important in future investigations into this class of complexes. [ABSTRACT FROM AUTHOR]

This study explores the interactions between hexanal Schiff bases and a B12N12 nanocage, employing density functional theory (DFT) calculations to deepen our understanding of noncovalent bonds. Hexanal, a key component in tea, plays a vital role in prolonging the shelf-life of various plant-based products by inhibiting phospholipase-D. Our research initially focused on synthesizing Schiff bases through the condensation of hexanal with nucleobases and an amino acid. We then conducted a series of DFT calculations, including geometry optimizations, frontier molecular orbital (FMO), natural bond orbital (NBO) and noncovalent interactions (NCI) assays, using Gaussian 16 and ORCA 5.0.2 software packages. This study reveals that hexanal Schiff bases form stable complexes with the B12N12 nanocage, exhibiting notable dative coordinate bonding. The FMO analysis indicates a significant energy gap variation among the complexes, with CSB2 showing the lowest energy gap, hinting at its high reactivity. In the LED assay, CSB2 demonstrates the lowest decomposition energy, highlighting its potential stability. The AIMD simulations provide insights into the electronic motions of these complexes, underscoring their dynamic nature. Our NBO analysis offers a comprehensive view of the electron distribution within these complexes, emphasizing the significance of nitrogen and boron atoms in the bonding process. The NCI assay sheds light on the predominant van der Waals and steric interactions contributing to the stability of the complexes. This investigation provides a detailed account of the NCI between hexanal Schiff bases and the B12N12 nanocage. The findings not only contribute to the field of noncovalent bonding in inorganic- fullerene structures but also open avenues for future applications in material science and molecular engineering. [ABSTRACT FROM AUTHOR]

Vitrimer materials have machinability and stability because of their shape remodeling and self‐healing properties at high temperatures. This article reports the synthesis of epoxy resin using vanillin, p‐aminophenol, and epichlorohydrin as raw materials, and polyetheramine‐400 as a curing agent. To study the effect of free amine on the mechanical and self‐healing properties, two materials with epoxy and amine stoichiometric ratios of 1:1 and 1:1.2 were studied, respectively. The experimental results show that when the molar ratio of epoxy to amine stoichiometric is 1:1.2 (V1:1.2), the tensile strength of vitrimer materials can reach 5.4 MPa and the self‐healing efficiency can reach 99.5% after 6 h of healing at 120°C. When the molar ratio is 1:1 (V1:1), the obtained epoxy material has a higher tensile strength of 9.5 MPa. After 24 h of healing at 120°C, the self‐healing efficiency can reach 83.4%. In addition, epoxy vitrimer materials can be remodeled at 120°C, and the self‐healing and mechanical properties are not influenced after remodeling. This work proposes a novel preparation method for epoxy vitrimer materials, which is beneficial to the development of high‐strength remodelable self‐healing materials. [ABSTRACT FROM AUTHOR]

This study reports the synthesis and computational investigation of two Schiff bases: (E)-N-(4-bromophenyl)-1-(2,6-dichlorophenyl)methanimine (S1) and (E)-4-(((4-bromophenyl)imino)methyl)phenol (S2), with a focus on their potential antibacterial activity. Schiff bases, known for their versatility and application in medicinal chemistry, are synthesized through the condensation reactions of the appropriate aniline with aldehydes. The molecular structures of S1 and S2 were elucidated using basic spectroscopic methods such as Fourier-transform-infrared, ultraviolet-visible as well as ¹H and 13C-NMR, while the purity of the compounds was ascertained using elemental analysis. The stability, chemical reactivities, and electronic properties of S1 and S2 were evaluated using Density Functional Theory (DFT). The energy band gap (ΔE) of S1 and S2 is 2.81 eV and 3.02 eV, respectively, and this infers that S1 is more reactive as well as less stable than S2. The molecular electrostatic potential (MEP) mapping evaluation showed that both S1 and S2 have more of the yellow, green, and red regions than the blue region, signifying that these structures are prone to electrophilic attack. The compounds were screened against two Gram-negative (Klebsiella pneumoniae and Pseudomonas aeruginosa) and one Gram-positive bacteria (Staphylococcus aureus) to evaluate their antibacterial potential. S1 as well as S2 showed antibacterial potential against Staphylococcus aureus and exhibited less or no activity against Klebsiella pneumoniae and Pseudomonas aeruginosa. In silico studies of S1 and S2 against Staphylococcus aureus were carried out, and the outcomes corroborated the experimental findings. Pharmacological evaluation of S1 and S2 showed that both compounds exhibited less violation of Lipinski’s rule of five (Ro5), which makes them less toxic and orally available. [ABSTRACT FROM AUTHOR]

Nanotechnology has ushered in significant advancements in drug design, revolutionizing the prevention, diagnosis, and treatment of various diseases. The strategic utilization of nanotechnology to enhance drug loading, delivery, and release has garnered increasing attention, leveraging the enhanced physical and chemical properties offered by these systems. Polyamidoamine (PAMAM) dendrimers have been pivotal in drug delivery, yet there is room for further enhancement. In this study, we conjugated PAMAM dendrimers with chitosan (CS) to augment cellular internalization in tumor cells. Specifically, doxorubicin (DOX) was initially loaded into PAMAM dendrimers to form DOX-loaded PAMAM (DOX@PAMAM) complexes via intermolecular forces. Subsequently, CS was linked onto the DOX-loaded PAMAM dendrimers to yield CS-conjugated PAMAM loaded with DOX (DOX@CS@PAMAM) through glutaraldehyde crosslinking via the Schiff base reaction. The resultant DOX@CS@PAMAM complexes were comprehensively characterized using Fourier-transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). Notably, while the drug release profile of DOX@CS@PAMAM in acidic environments was inferior to that of DOX@PAMAM, DOX@CS@PAMAM demonstrated effective acid-responsive drug release, with a cumulative release of 70% within 25 h attributed to the imine linkage. Most importantly, DOX@CS@PAMAM exhibited significant selective cellular internalization rates and antitumor efficacy compared to DOX@PAMAM, as validated through cell viability assays, fluorescence imaging, and flow cytometry analysis. In summary, DOX@CS@PAMAM demonstrated superior antitumor effects compared to unconjugated PAMAM dendrimers, thereby broadening the scope of dendrimer-based nanomedicines with enhanced therapeutic efficacy and promising applications in cancer therapy. [ABSTRACT FROM AUTHOR]

Photoisomerization is a key photochemical reaction in microbial and animal rhodopsins. It is well established that such photoisomerization is highly selective; all-trans to 13-cis, and 11-cis to all-trans forms in microbial and animal rhodopsins, respectively. Nevertheless, unusual photoisomerization pathways have been discovered recently in microbial rhodopsins. In an enzymerhodopsin NeoR, the all-trans chromophore is isomerized into the 7-cis form exclusively, which is stable at room temperature. Although, the 7-cis form is produced by illumination of retinal, formation of the 7-cis form was never reported for a protonated Schiff base of all-trans retinal in solution. Present HPLC analysis of retinal oximes prepared by hydroxylamine reaction revealed that all-trans and 7-cis forms cannot be separated from the syn peaks under the standard HPLC conditions, while it is possible by the analysis of the anti-peaks. Consequently, we found formation of the 7-cis form by the photoreaction of all-trans chromophore in solution, regardless of the protonation state of the Schiff base. Upon light absorption of all-trans protonated retinal Schiff base in solution, excited-state relaxation accompanies double-bond isomerization, producing 7-cis, 9-cis, 11-cis, or 13-cis form. In contrast, specific chromophore-protein interaction enforces selective isomerization into the 13-cis form in many microbial rhodopsins, but into 7-cis in NeoR. [ABSTRACT FROM AUTHOR]

Schiff bases are compounds that are widely distributed in nature and have practical value for industry and biomedicine. Another important use of Schiff bases is identifying metal ions and different molecules, including proteins. Their proneness to hydrolysis limits the utilization of Schiff bases to mainly non-aqueous solutions. However, by introducing –OH and –SH substituents to aromatic amine-bearing rings, it is possible to increase the resilience of the Schiff base to destruction in water. The present paper discusses how the hydroxyl or thiol group influences the spectral properties and kinetics of the hydrolysis and formation of Schiff bases derived from pyridoxal 5′-phosphate and aniline, 2-hydroxyaniline, and 2-mercaptoaniline using quantum chemical data. The spectral variation between different imines can be explained by taking into account the geometry and frontier molecular orbital alteration induced by the substituents. The changes in the hydrolysis rate are analyzed using the computed values of local reactivity indices. [ABSTRACT FROM AUTHOR]

AbstractA Schiff base (imine) ligand, (E)-4-((2-hydroxy-3,5-diiodobenzylidene)amino)-N-(4,6-dimethylpyrimidin-2-yl)benzenesulfonamide (HL), was synthesized by condensation of 3,5-diiodosalicylaldehyde with sulfamethazine. The ligand was then complexed with Zn(II), Cu(II), Ni(II), Co(II) and Fe(II) employing a metal to ligand ratio of 1:2 to form chelates (1-5), [M(L)2(H2O)2]. Characterization was done by UV-visible, FTIR, 1H and 13C NMR spectroscopy, elemental analysis, magnetic moments, thermogravimetric analyses (TGA) and conductance studies. The Schiff base behaved as a bidentate ligand and metal chelates assumed octahedral geometry. MOE-docking was employed to assess binding of the Schiff base (HL) and its chelates (1-5) with 1T2P, 1VVQ, 2W61, 3U2D, 4H8E and 5K18 proteins. Results indicated that Zn(II) chelate (1) and Fe(II) chelate (5) are the most potent compounds. Antibacterial and antibiofilm activities were executed against Enterococcus faecalis, Staphylococcus aureus, Proteus mirabilis and Klebsiella pneumoniae. Antifungal activities were performed against Candida albicans and Aspergillus niger. The Schiff base exhibited moderate antibacterial/antifungal activities that were enhanced on chelation with metal ions. Zinc(II) chelate (1) and Fe(II) chelate (5) show excellent antibacterial/antifungal activities. Complex 2 exhibited good antibiofilm activity. [ABSTRACT FROM AUTHOR]

Abstract\nHIGHLIGHTSA new Schiff base inhibitor known as “N, N’ carbonyl- Bis (para-hydroxy benzaldehyde imine)” has been synthesized and characterized by FTIR, NMR, and UV-Visible spectroscopy, the molecule was then assessed for its ability to prevent copper from corroding in a solution of 0.5 M H2SO4 using potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy SEM combined with energy dispersion spectroscopy EDX, and atomic force microscopy AFM. The tested inhibitor exhibits good copper corrosion inhibition performance in a 0.5 M H2SO4 solution. As inhibitor concentration rises, inhibition performance also rises, reaching a maximum inhibitory efficacy of around 84.76 ± 0.69% at 5.10−4 M. The inhibitor was adsorbable to the metal surface and followed the Langmuir isotherm. It has been done such that the addition of KI increased the inhibitory effectiveness, the mixed additives worked together. There is good agreement between the conclusions drawn from theoretical calculations using DFT and MD simulation and actual observations.A new Schiff base inhibitor has been synthesized.The inhibitory efficiency increase with increasing inhibitor concentration.The investigated molecule adsorbs on the copper surface through active centers like N and O.The synthesized molecule has good inhibitory effectiveness with respect to copper corrosion in an acidic medium.A new Schiff base inhibitor has been synthesized.The inhibitory efficiency increase with increasing inhibitor concentration.The investigated molecule adsorbs on the copper surface through active centers like N and O.The synthesized molecule has good inhibitory effectiveness with respect to copper corrosion in an acidic medium. [ABSTRACT FROM AUTHOR]

In this study, a series of new chelating copolymers containing 20% azomethine groups, poly(N-vinylpyrrolidone-co-vinylsalicylideneimine) (poly[VP-co-VSalI]), poly(N-vinylpyrrolidone-co-vinylpicolinideneimine) (poly[VP-co-VPicI]), poly(N-vinylpyrrolidone-co-vinylpyridoxylideneimine) (poly[VP-co-VPyrI]) with M = 63000 Da and their vanadium(IV) complexes – poly(VP-co-VSalI)-VO, poly(VP-co-VPicI)-VO, poly(VP-co-VPyrI)-VO, were designed and synthesized. These are intended for the delivery and pH-dependent release of vanadium species in the intestine environment. The chelating polymers were obtained from poly(N-vinylpyrrolidone-co-N-vinylamine) (poly[VP-VAm]) by polymer-analogous transformations with the corresponding aldehydes. The vanadium content, determined by ICP-AES and spectrophotometric methods, was 5.36%, 4.99%, and 9.1% of the dry mass for poly(VP-co-VSalI)-VO, poly(VP-co-VPyrI)-VO, and poly(VP-co-VPicI)-VO, respectively. XPS data confirmed that only vanadium(IV) is presented in the complexes. All complexes demonstrated a pH-dependent release of low molecular weight vanadium species, making them promising candidates for the development of vanadium-containing systems for oral administration. These systems protect the main vanadium content in the stomach but can release biologically active ions in the intestine. [ABSTRACT FROM AUTHOR]

Objective: This study involved synthesis of a new series of different five-membered heterocyclic derivatives, testing their antioxidant activity, and examining their potential in vitro antimicrobial agents. Methods: The synthesis of the derivatives involved a three-step process. Initially, succinyl chloride was reacted with methanol, followed by a reaction with 80% hydrazine hydrate through a nucleophilic addition-elimination mechanism, resulting in the formation of succinohydrazide (I). This compound was then employed as a precursor for the synthesis of Schiff bases (II), and (III) by reacting it with m-nitro benzaldehyde and p-nitro benzaldehyde. Following this, a ring closure reaction was applied using thioglycolic acid, glycolic acid, and glycine, resulting in the synthesis of different five-membered heterocyclic rings (IV–IX). Results and Discussion: The formation of the prepared derivatives was confirmed by FT-IR, 1H NMR, and 13C NMR spectroscopy. Comparative analysis with L-ascorbic acid as a standard revealed that all the prepared compounds exhibited excellent antioxidant activities. In terms of antimicrobial activity, the tested derivatives showed moderate activity against both positive and negative types of bacteria, when compared to the reference drug Ciprofloxacin. Additionally, the antifungal test showed moderate activity for all the tested compounds against a specific pathogenic fungus, with Clotrimazole being as the reference drug. The antimicrobial activity of the synthesized compounds was found to be dependent on the type of heterocyclic rings containing S, O, and N atoms. These atoms were observed to enhance antimicrobial activity by donating electrons and becoming active. Additionally, the presence of active functional groups such as C=O, NO2, and C=N contributed to this observed result. Conclusions: All of the synthesized compounds have demonstrated excellent antioxidant agents. Most of them have shown promising antimicrobial activity against certain bacteria strains, and effectiveness against a pathogenic fungus. [ABSTRACT FROM AUTHOR]

Objective: This research aims to synthesize and characterize a new series of bioactive quinazoline derivatives, including Schiff bases, biquinazolinone, and benzothiazine, and to evaluate their bioactivity as antioxidants through both in silico and in vitro investigations. Methods: The new derivatives were synthesized with high yields by reacting Schiff base derivatives of quinazoline with 2-aminobenzoic acid and 2-mercaptobenzoic acid. The characterization of the prepared derivatives was carried out using FTIR, 1H NMR, and 13C NMR techniques. In silico investigations included assessing pharmacokinetic and pharmacodynamic properties through the SwissADME online server and conducting molecular docking studies with the tyrosinase enzyme. In vitro assessments involved evaluating antioxidant activity using the total antioxidant capacity method and the DPPH scavenging activity method. Results and Discussion: In silico analysis revealed favorable pharmacokinetic and pharmacodynamic properties for all compounds. Compounds (III) and (IV) exhibited acceptable pharmacological characteristics. Molecular docking studies showed good docking scores for all compounds with the tyrosinase enzyme. In vitro assessments demonstrated noteworthy to excellent antioxidant activity for all compounds, with compounds (III) and (IV) exhibiting very strong activity compared to the standard reference, ascorbic acid. Conclusions: The synthesized quinazoline derivatives exhibit promising bioactivity as antioxidants, supported by both computational and experimental assessments. These findings suggest their potential for further exploration in the development of antioxidant agents, with particular emphasis on the notable performance of compounds (III) and (IV). [ABSTRACT FROM AUTHOR]

Objective: The aim of this study is to produce novel 4(3H)-quinazolinone derivatives, analyze their efficacy as antibacterial and antifungal agents, and investigate their antioxidant abilities. Methods: New quinazolinone derivatives were synthesized by mixing Schiff bases with three different chemicals: phenyl isocyanate, 4-chlorophenyl isocyanate, and phenyl iso thiocyanate. This resulted in the formation of compounds (VIa–VIb), (VIIa–VIIb), and (VIIIa–VIIIb). The efficacy of these synthesized compounds against bacteria and fungi was evaluated. Subsequently, their antioxidant activity was assessed using the DPPH scavenging method. Results: FT-IR, 1H NMR, and 13C NMR spectroscopy were used to investigate all the prepared derivatives. Compounds (VIIb), (VIIIa), and (VIIIb) exhibited good antioxidant activity when compared to ascorbic acid. Discussion: The presence of the quinazolinone nucleus in some compounds gives them good biological properties as antimicrobials and antioxidants. Conclusions: All the synthesized compounds were highly effective at killing fungi, especially Rhizopus microrhizosporium, and Candida. Most of them were also very effective at killing bacteria like E. coli, Bacillus cereus, and Pseudomonas aeruginosa. Although most of these compounds have relatively moderate effectiveness against Staphylococcus aureus, some of them contain good antioxidants, particularly compound (VIIIb). [ABSTRACT FROM AUTHOR]

Objective: The synthesis, antibacterial, and antioxidant assessment of novel tetrazole derivatives with the 2-amino-5-(4-nitrophenyl)-1,3,4-thiadiazole moiety are the main objectives of this work. Methods: A multi-step procedure was used to synthesis the desired compounds, beginning with the creation of the thiadiazole core and ending with the functionalization of tetrazole rings. Results and Discussion: 2-Amino-5-(p-nitro phenyl)-1,3,4thiadiazole (I) was prepared by reacting p-nitro benzoic acid with thiosemicarbazide in the presence of POCl3. Compound (I) then underwent a reaction with 2-chloroacetohydrazide to produce 2-(5-(4-nitrophenyl)-1,3,4thiadiazol-2-yl)acetohydrazide (II). Several new Schiff bases (IIIa–IIId) were synthesized by reacting compound (I) with different aromatic aldehydes. In contrast, tetrazole derivatives (IVa–IVd) were produced by reacting Schiff bases derivatives (IIIa–IIId) with sodium azide. NMR and infrared spectroscopy were among the spectroscopic methods used to confirm the structures of the produced compounds. Using standard disc diffusion and broth dilution techniques, the antibacterial activity of these derivatives was evaluated against a panel of Gram-positive and Gram-negative bacteria. Additionally, radical scavenging assays was used to assess the antioxidant potential. The results showed that a number of the produced tetrazole derivatives have notable antioxidant and antibacterial properties. Conclusions: These results imply that 2-amino-5-(4-nitrophenyl)-1,3,4-thiadiazole scaffold-containing tetrazole derivatives may be good candidates for the synthesis of novel medicinal medicines with combined antioxidant and antibacterial capabilities. [ABSTRACT FROM AUTHOR]

Objective: Efficient synthesis of isatin Schiff's bases (IIIa–IIId) and isatin-derived 1,3,4-oxadizoles (IVa–IVd) and evaluation of their in vitro antibacterial, antifungal, and anti-TB activities. The molecular docking studies were performed with protein New Delhi Metallo-Beta-lactamase-1 and Mycobacterium tuberculosis enoyl reductase and molecular dynamics simulation. Methods: The chemical structures were confirmed by IR, NMR, and mass spectroscopic techniques. The biological screenings were studied for the foresaid compounds for their in vitro antibacterial, antifungal, and anti-TB activity using MIC method. Molecular docking and dynamics simulation studies were conducted using AutoDock software with proteins New Delhi Metallo-Beta-lactamase-1 (NDM-1, PDB ID: 3ZR9) and Mycobacterium tuberculosis enoyl reductase (INHA, PDB ID: 4TZK). Results and Discussion: The compounds (IVa–IVc) displayed excellent in vitro antimicrobial activity. Also, the compounds (IVa–IVc), were found to be most active with a MIC of 3.125 µg/mL. For the docked proteins, all the compounds exhibited a substantial binding affinity. Further, molecular dynamics were disclosed for compounds (IVa–IVc). Conclusions: The compounds (IIIa–IIId) and (IVa–IVd) were synthesized from substituted isatins, p-amino benzoic acid, and isoniazid with moderate to excellent yields. These reactions are simple, convenient, and hitherto novel. In docking studies the compounds (IVa–IVc) showed excellent bind affinity towards the enzymes. [ABSTRACT FROM AUTHOR]

A new bidentate Schiff base ligand (C16H16Cl2N4), condensation product of ethylene diamine and 4-chloro N-phenyl formamide, and its metal complexes [M(C16H16Cl2N4)2(OAc)2] (where M = Mn(II) and Zn(II)) were synthesized and characterized using various analytical and spectral techniques, including high-resolution mass spectrometry (HRMS), elemental analysis, ultraviolet-visible (UV-vis), Fourier-transform infrared (FTIR) spectroscopy, AAS, molar conductance, 1H NMR, and powder XRD. All the compounds were non-electrolytes and nanocrystalline. The synthesized compounds were assessed for antioxidant potential by DPPH radical scavenging and FRAP assay, with BHT serving as the positive control. Inhibitory concentration at 50% inhibition (IC50) values were calculated and used for comparative analysis. Furthermore, the prepared compounds were screened for antibacterial activity against two Gram-negative bacteria (Staphylococcus aureus and Bacillus subtilis) and two Gram-positive bacteria (Escherichia coli and Salmonella typhi) using disk-diffusion methods, with amikacin employed as the standard reference. The comparison of inhibition zones revealed that the complexes showed better antibacterial activity than the ligand. To gain insights into the molecular interactions underlying the antibacterial activity, the ligand and complexes were analyzed for their binding affinity with S. aureus tyrosyl-tRNA synthetase (PDB ID: 1JIL) and S. typhi cell membrane protein OmpF complex (PDB ID: 4KR4). These analyses revealed robust interactions, validating the observed antibacterial effects against the tested bacterial strains. [ABSTRACT FROM AUTHOR]

Thanks to the ability of diazo derivatives to react either as 1,3‐dipoles and as carbenes after dinitrogen extrusion, combinations of oxa or aza benzonorbornadienes and diazomalonates afford polycyclic pyrazolidines via a three‐step sequence of (i) a highly diastereoselective [3+2]‐cycloaddition, (ii) a CpRu‐catalyzed carbene addition, and (iii) a second dipolar cycloaddition. Of importance, step (II) represents a unique access to novel bench‐stable N,N‐cyclic azomethine imines, which behave as effective 1,3‐dipoles in combination with electron‐poor dipolarophiles. Each step proceeds efficiently and the 3‐step process can be performed in one‐pot to yield a polycyclic pyrazolidine in excellent overall yield (90 %). [ABSTRACT FROM AUTHOR]

Combining exogenous and endogenous antibacterial mechanisms has been demonstrated to enhance therapeutic efficacy significantly. This study constructs an innovative type of exogenous and endogenous antibacterial nanocomposite hydrogels with injectable dual‐crosslinked networks and dual‐stimuli responsiveness. The primary network establishes imine bonds between the functionalized dextran featuring norbornenes and aldehydes (NorAld‐Dex) and the quaternized chitosan (QCS). The imine bonds provide self‐healing, injectability, and pH‐responsiveness to the hydrogel network. The secondary network is established by integrating thiolated mesoporous silica‐coated titanium dioxide nanoparticles (TiO2@MS‐SH) into the hydrogel network via an ultrasound‐activated thiol‐norbornene reaction with NorAld‐Dex. The microstructures and properties of NorAld‐Dex/QCS/TiO2@MS‐SH hydrogels can be fine‐tuned by adjusting the sonication time to increase the amount of thiol‐norbornene crosslinks in the network. Effective antibacterial performance of NorAld‐Dex/QCS/TiO2@MS‐SH hydrogels at low pH has been demonstrated with the synergistic effect of the acid‐induced dissociation of the hydrogel network, protonated QCS, and the reactive oxygen species (ROS) generated by TiO2@MS‐SH nanoparticles under ultrasound irradiation. In summary, NorAld‐Dex/QCS/TiO2@MS‐SH nanocomposite hydrogel is an advanced dual stimuli‐responsive antibacterial platform with customizable microstructures and properties, offering great potential for biomedical applications. [ABSTRACT FROM AUTHOR]

Fluorescent probes incorporating the excited-state intramolecular proton transfer (ESIPT) phenomenon have emerged as versatile tools in scientific research. These probes exhibit dual emission, resulting from the unique transfer of a proton within the molecule upon excitation. This property makes ESIPT-based Schiff bases highly attractive for metal detection, cell imaging, and sensing biologically important molecules. In metal detection, the spectral changes of ESIPT-based Schiff bases upon interaction with metal ions enable the development of sensitive and selective sensors. For cell imaging, their photophysical properties make them ideal for labeling cellular components and facilitating multicolor imaging. In sensing biomolecules, ESIPT-based Schiff bases offer selective detection of interactions and enzymatic activities. Integration of these probes holds great promise for applications in environmental monitoring, biomedical research, and healthcare. This review focuses on the photoluminescent properties and application of ESIPT dual emission Schiff bases for sensing of metal ions, biologically relevant molecules and cell imaging. [ABSTRACT FROM AUTHOR]

Isatin-derived Schiff bases are the subject of many studies, finding wide application areas in polymer technology, pharmaceutical industry, and medicine. In this study, a series of new Schiff bases were prepared from monothiocarbohydrazones based on isatins with different substituents (5-F, 5-Br, 5-I, and 5-MeO). The chemical structures of the synthesized compounds were determined using 1H NMR, 13C NMR, FTIR spectroscopic techniques, and elemental analysis. Antioxidant activity determinations of 23 compounds were performed using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical quenching method. The highest percent inhibition value at 10 µM concentration was shown by compound number 22, 5-bromoisatin Schiff base containing 3-methoxy-4-hydroxy group. Compound 17, a 5-iodoisatin Schiff base containing 3-methoxy-4-hydroxy group, showed the highest antioxidant activity with an IC50 value of 9.76 ± 0.03 µM. In addition to the theoretical analysis of the compounds, both their spectroscopic and antioxidant properties were investigated. The ground-state geometries and some chemical reactivity parameters of the compounds were calculated using the B3LYP/6-311 + + G(2d,2p) approach. Besides intramolecular interactions, substituent effects, and some QTAIM parameters, the calculations were also performed to study the electronic properties of reactive N/O–H bonds and were used to interpret the experimental results. The effects of the electronic parameters and intramolecular interactions of reactive N/O–H bonds on the antioxidant properties of the compounds were investigated. Additionally, the relationships of DPPH reactions with delocalization indices of N/O-H bonds and the pattern of SET/HAT mechanisms with electronic variables were analyzed. Examination of electron and hydrogen atom transfer mechanisms has shown the dominance of electron transfer, supported by the correlation coefficients between IC50 values and SET reaction energies. [ABSTRACT FROM AUTHOR]

Triphenylamine (TPA)‐based Schiff base chemosensors ((E)‐2‐((4‐(diphenylamino)benzylidene)amino)phenol [TPA‐AP], (E)‐5‐(diphenylamino)‐2‐(((2‐hydroxyphenyl)imino)methyl)phenol [HTPA‐AP], and (E)‐5‐(diphenylamino)‐2‐((phenylimino)methyl)phenol [HTPA‐A]) were synthesized and explored the role of metal chelating hydroxyl functionality position for heavy metal ion sensing. TPA‐AP and HTPA‐AP showed Cu2+ ion‐induced chemical transformation and produced oxazole derivatives with turn‐on fluorescence. In contrast, HTPA‐A exhibited metal chelation‐induced turn‐on fluorescence for Zn2+ ion. The reactive chemical sensing of TPA‐AP and HTPA‐AP led to high selectivity of Cu2+, and other ions did not show any interference. The concentration‐dependent studies of Cu2+ and Zn2+ indicated the limit of detection (LOD) up to 6.07 × 10−7 and 4.6 × 10−7 M, respectively. Further, Cr3+, Fe3+, and Fe2+ coordination with TPA‐AP and HTPA‐AP exhibited visible color change from colorless to yellow. However, the yellow color was disappeared and becomes colorless due to imine hydrolysis. Interestingly, all three metal ions showed different rate of hydrolysis and color disappearance. TPA‐AP with Fe3+ exhibited fast hydrolysis and immediate color change whereas Fe2+ and Cr3+ required longer time. But HTPA‐AP and HTPA‐A produced stable complexes with Cr3+, Fe2+, and Sn2+ and Fe3+ alone showed hydrolysis. Thus, the present studies provide structural insight for designing reactive fluorescence and colorimetric Schiff base chemosensor for heavy metal ions. [ABSTRACT FROM AUTHOR]

Two copper (II) complexes based on the mixed ligand system were synthesized and structurally characterized. The molecular formulae for complex (1), [Cu2L1L′] and complex (2), [CuL2L′] were determined based on analytical data, molar conductance, and thermal analysis results. The optimized structures of complexes (1) and (2) were determined by magnetic and spectroscopic measurements (FTIR, UV–Vis, and ESR) and confirmed by processing powder X‐ray diffraction data by Expo 2014 software. The geometry index (τ5), determined by ESR spectra and structural analysis based on powder X‐ray, demonstrates the square pyramidal geometry of the Cu (II) center of [Cu2L1L′] and [CuL2L′]. Cyclic voltammetry measurements were performed to elucidate the relationship between the redox properties of (1) and (2) and their oxidase‐mimicking catalytic activity. Catalytic aerobic oxidation of the polyphenols 3,5‐di‐tert‐butylcatechol (3,5‐DTBCH2), 4‐nitrocatechol, and 2‐aminophenol (2‐APH3) was studied by stopped‐flow technique. Promising catechol oxidase (COX) and phenoxazinone synthase (PHS) mimetic activity have been demonstrated for (1) and (2). Electrochemical data were used to determine the free energy (ΔG°) or driving force (−λ), and their correlation with the oxidase mimetic activity of(1) and (2) was examined. Several experimental procedures have been performed that have helped describe the catalytic mechanisms of the catalytic reactions taking place. [ABSTRACT FROM AUTHOR]

The new Schiff base ligand was designed from a condensation reaction of isatin with 5‐amino‐2‐hydroxy benzoic acid. Then, the metal complexes were prepared. The structures of the prepared compounds were framed from thermogravimetric analyses (TG–DTG), mass spectrometry, elemental analyses, 1H‐NMR, IR, electronic spectra, UV–vis, and conductivity measurements. Surface and size morphology have been studied by X‐ray powder diffraction and scanning electron microscope (SEM) analysis. The IR spectra suggested that the ligand acted as bidentate coordinated with metal ions through deprotonated carboxylate oxygen atom and oxygen of phenolic group. With the exception of the complexes of Cr (III), Fe (III), and Cd (II), which were non‐electrolytes, the molar conductivities demonstrated the electrolytic behavior of all the rest complexes. The X‐ray diffraction (XRD) analysis patterns for the Schiff base complexes indicated their crystalline nature except the Co (II) complex which had amorphous structure. The ligand and its metal complexes were screened for their antimicrobial activities against two G‐positive, two G‐negative bacteria and against Aspergillus fumigatus and Candida albicans fungi. Additionally, the compounds were evaluated against the MFC‐7 breast cancer cell line for their anticancer activity. The outcomes demonstrated their strong antitumor activity. [Fe(HL)Cl2(H2O)2]0.5H2O complex has the lowest IC50 value = 9 μg mL−1. Molecular modeling studies for the ligand and its Co (II) and Fe (III) complexes were accomplished from density functional theory (DFT) analysis. From molecular docking study, the electrophilic moieties in both complexes displayed good binding interactions with the CDK6, aminoglycoside phosphotransferase, and CYP51 targeted proteins. [ABSTRACT FROM AUTHOR]

Nickel(II) complexes of tridentate NNO donor aroylhydrazones, viz., di‐2‐pyridyl ketone‐4‐methoxybenzhydrazone monohydrate (DKMBH·H2O) and 2‐acetylpyrazine‐4‐methoxybenzhydrazone monohydrate (APMBH·H2O), were synthesized and characterized using various methods, including spectral techniques (Fourier transform infrared [FT‐IR], UV–vis) and analytical methods (elemental and X‐ray diffraction [XRD] analysis). Single‐crystal XRD was used to elucidate the crystal structures of nickel(II) complexes 1 and 2. The XRD analysis revealed that the respective ligands coordinated to the Ni(II) center through the deprotonated iminolate form in complex 1 and the neutral amido form in complex 2, resulting in distorted octahedral geometries. The ground state electronic configurations of the complexes were studied using the B3LYP/UB3LYP levels of DFT. Using absorption spectral titration methods, the interactions of complexes with CT‐DNA and bovine serum albumin (BSA) protein were examined. The observed data demonstrate that the complexes adopt an intercalative binding mode to bind to CT‐DNA and BSA protein. Additionally, the antioxidant activity of the nickel(II) complexes and their ligands was determined using 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH). Complex 2 demonstrated the highest radical scavenging activity of the compounds studied (IC50 = 3.81 mM). Furthermore, molecular docking studies were performed to understand how the complexes can interact with the SARS‐CoV‐2 main protease. The results revealed that complex 2 had the highest docking score (−8.18 kcal/mol) when compared with the other complexes under study. Aside from their biological properties, the nickel complexes heterogenized on functionalized SBA‐15 showed promising catalytic activity, achieving 98% yield in the reduction of nitrobenzene, forming exclusively aniline as the end product. [ABSTRACT FROM AUTHOR]

Katiragum dialdehyde‐tryptophan Schiff base (KGDT) is developed for selective and efficient detection of Cd2+ ion and hydroquinone (HQ) in the aqueous medium by electrochemical method. KGDT is synthesized by selectively oxidizing the C2‐C3 bond of katiragum with sodium meta periodate (NaIO4) to obtain katiragum dialdehyde (KGD), followed by condensation between KGD and an α‐amino acid (L)‐tryptophan. KGD and KGDT are characterized by 1HNMR, HRMS, and FESEM with EDAX analysis. The electrochemical experiment is carried out by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods. The electrochemical sensing toward the Cd2+ ion in the DPV method is found to be better compared to the CV method. In the CV method, the limit of detection (LOD) values of Cd2+ ion and HQ are calculated as 8.84 nm and 15.91 nm, respectively. In the DPV method, the LOD values of Cd2+ ion and HQ are found to be 7.24 nm and 15.29 nm, respectively. The proposed sensor, KGDT/GCE, shows satisfactory results in the stability and reproducibility test and also shows excellent practical applicability in real sample analysis. [ABSTRACT FROM AUTHOR]

Due to the significant pharmacophoric role of 1,4‐naphthoquinone moiety, which is found in numerous biologically active natural products and well‐known chemotherapeutic drugs, including doxorubicin, shikonin, and alkannin, a newly prepared ligand ((E)‐1‐((2‐mercaptophenyl)imino)naphthalen‐2(1H)‐one) can be obtained from the condensation of 2‐aminothiophenol with diketone (1,2‐naphthoquinone) to form Schiff base (HL), which has been characterized using elemental analyses, FT‐IR, 1H‐NMR, and mass spectra. The inner ((La(III), Er(III), and Yb(III)) and outer ((Fe(III), Co(II), and Zn(II)) transitionmetal complexes have been prepared in 1:2 ratio and identified by several spectroscopic instruments. Different characterization tools have been used as elemental analyses, 1H‐NMR, molar conductivity, 13C‐NMR, FT‐IR, thermal decomposition (TG and DTG), UV‐vis, X‐ray diffraction, mass spectrometry, solid reflectance, and magnetic moment. All of them are conjugated to confirm the proposed structures of the metal complexes and are complementary. Also, molecular docking studies for the ligand and its Zn(II) and Yb(III) complexes (using MOE program) have been performed to support the experimental biological activity. Molecular docking studies recommended that (Yb(HL)2)Cl3·6H2O complex is more potent against Aspergillus niger fungus when docked with 1Y43 (aspergilloglutamic peptidase enzyme from A. niger) receptor, while Zn(II) complex recorded the strongest binding energy among the docked compounds against 2W3Z(the crystal structure of a Streptococcus mutans CE4 esterase) and 7AB4 (the crystal structure of the Escherichia coli toxin‐antitoxin system HipBST [HipT S59A]) proteins receptors, respectively. Experimental applications of the free ligand and its metal chelates as antimicrobial and antioxidant activities have been carried out. The former occurred against two fungal species (Aspergillus niger [ATCC:16404] and Candida albicans [ATCC:10231]), two G‐positive bacterial species (S. mutans [ATCC:25175] and Staphylococcus aureus [ATCC:13565]) and two G‐negative bacterial species (Klebsiella pneumonia [ATCC:10031] and E. coli [ATCC:10536]). The DPPH scavenging method has been used to measure the antioxidant activity of the tested compounds. [ABSTRACT FROM AUTHOR]

For synthesizing metal–organic molecules with pro‐drug properties to prevent the accumulation of amyloid beta (Aβ1–42), which is a feature of neurodegenerative Alzheimer's disease, two new Schiff bases with imine/amine donors 2‐([3,3‐diphenylalidene]amino)‐N,N‐dimethylethane‐1‐amine and N,N‐dimethyl‐2‐([quinolin‐4‐ylmethylene]amino)ethane‐1‐amine, as well as their novel Pt (II) complexes (I and II), were synthesized and characterized via Fourier transform infrared spectroscopy, 1H‐ and 13C‐nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and elemental analyses. The spectroscopic data has shown that the ligands are coordinated to the central atom in a chelating manner. Furthermore, the interaction between these complexes and Aβ1–42 was investigated using the electrochemical methods, square wave voltammetry and pencil graphite electrode, while monitoring the changes in the oxidation signal of the Try residue in Aβ1–42. The ability of the compounds to inhibit Aβ1–42 aggregation was investigated using the human neuroblastoma cell line (SH‐SY5Y). Complex II could actively inhibit the aggregation of Aβ1–42 at a molar ratio of 1.0/1.0, and its Aβ1–42 aggregation kinetics were fluorometrically determined using thioflavin T. These results were supported by scanning electron microscopy and transmission electron microscopy analyses. Moreover, the interaction of complex II with Aβ1–16 was investigated via 1H‐NMR spectroscopy. As a result, it was observed that complex II was effective in inhibiting the aggregation of Aβ1–42 at a molar ratio of 1.0/1.0. This result shows that studies can be conducted on the effects of Schiff base‐Pt complexes as potential pro‐drugs on Alzheimer's disease. [ABSTRACT FROM AUTHOR]

J‐aggregation and H‐aggregation are identified as two classical models of functionally oriented non‐covalent interactions, and significant attention has been drawn by researchers. However, due to the scarcity of single‐crystal examples of H‐aggregation, a comprehensive understanding of the relationship between its stacking mode and optical behaviour has been hindered. In recent studies, two polyaromatic Schiff base compounds, Cl‐Salmphen and H‐Salmphen, were successfully synthesized, and both were found to exhibit H‐aggregation. In the findings, H‐Salmphen was shown to display typical C─H···π interactions, characteristic of Aggregation‐Induced Emission (AIE) active molecules, whereas its halogenated counterpart was identified as behaving similar to Aggregation‐Caused Quenching (ACQ) active molecules. These types of results suggest that identical intermolecular interactions can produce differing optical behaviours. Light was shed, at least in part, on the formation mechanisms of H‐type aggregates and their luminescence properties from these observations. Additionally, the high optical signal‐to‐noise ratio inherent to H‐aggregates was utilized for the exploration of water content detection. As an outcome, a high‐performance fluorescent filter paper was developed, enabling easy real‐time detection using a smartphone. [ABSTRACT FROM AUTHOR]

This study explores the compelling antitumor properties of VALD‐2, a synthetic Schiff base ligand known for its low toxicity. The focus is on investigating VALD‐2's protective role against cisplatin‐induced acute kidney injury (AKI) in mice, with a specific emphasis on mitigating oxidative stress and inflammation. The study involves daily intraperitoneal injections of amifostine or VALD‐2 over 7 days to establish an AKI model. Subsequently, mice were assigned to normal control, cisplatin group, cisplatin + amifostine group, and cisplatin + VALD‐2 10 mg/kg group, cisplatin + VALD‐2 20 mg/kg, and cisplatin + VALD‐2 40 mg/kg. Kidney injury is assessed through serum blood urea nitrogen (BUN) and creatinine (Cr) activity assays. Levels of inflammatory factors, tumor necrosis factor‐α (TNF‐α) and interleukin‐6 (IL‐6), in kidney tissue of mice were assessed through enzyme‐linked immunosorbent assay (ELISA). The protective effect of VALD‐2 is further examined through HE staining to observe pathological changes in kidney injury. The ultrastructural changes of renal cells and tubular epithelial cells were observed by electron microscopy under experimental conditions, indicating the effect of VALD‐2 on reversing cisplatin‐induced renal injury. The study delves into VALD‐2's protective mechanisms against cisplatin‐induced kidney injury by using western blot analysis to assess the expression levels of superoxide dismutase (SOD), glutathione peroxidase (GSH‐Px), and malondialdehyde (MDA) in kidney tissues. VALD‐2 demonstrates significant improvement in cisplatin‐induced AKI, as evidenced by increased BUN and Cr levels. It effectively protects kidney tissue from oxidative damage, enhancing SOD and GSH‐Px activities while reducing MDA levels. The study also reveals a decrease in TNF‐α and IL‐6 levels, supported by ELISA results, and histological findings confirm anti‐nephrotoxic effects. Western blot analysis shows an upregulation of antioxidant enzymes (SOD, GSH‐Px) and a reduction in MDA production. VALD‐2 emerges as a promising mitigator of cisplatin‐induced AKI, showcasing its ability to enhance oxidative stress‐related protein expression. The findings suggest VALD‐2 as a potential therapeutic agent for protecting against cisplatin‐induced kidney injury. Highlights: VALD‐2 is a yellow precipitate, a Schiff base ligand synthesized by mixing diethylene‐triamine and o‐vanillin and insoluble in 0.9% sodium chloride. It has been also reported that which forms complexes with most metals and has potential antibacterial, antiviral, and anticancer effects.In our previous study, we found that VALD showed antitumor effects both in vivo and in vitro. In recent years, the antitumor activities of some Schiff base ligands have been widely reported.Our study revealed for the first time that VALD‐2 alleviates cisplatin‐induced acute renal injury by inhibiting renal inflammation and enhancing the endogenous antioxidant system, which provides a molecular basis for the new drug treatment of cisplatin‐induced acute renal injury. [ABSTRACT FROM AUTHOR]