Search Results (1,391)

A new class of Ln(III) Schiff base (SB) complexes has been synthesized with the general formula [LnL(hfac)₃], where Ln = Tb (TbL), Eu (EuL), Sm (SmL) or Gd (GdL). The molecular structure of the complex was determined using the X-ray diffraction method. The IR spectra show that the C=O stretching is shifted from 1695 cm⁻¹ in pure PMMA to 1719–1724 cm⁻¹ in LnL-PMMA hybrid materials. This means that LnL materials are successfully embedded into the PMMA backbone in the polymeric films. However, the Ln(III) SB complexes exhibit emission spectra that cover the visible region. The TbL complex displays an intense green emission combined with a large emission lifetime of 0.505 ms. However, the incorporation of Ln-SB complexes into PMMA (polymethylmethacrylate) polymeric films was investigated. The thermal stabilities of the LnL-PMMA hybrid materials increased from 140 to 250 °C when compared with the LnL-SB complexes. Furthermore, their luminescence intensity and lifetimes were also enhanced due to their induced structural rigidity. The molecular interactions of the LnL complexes with the PMMA matrix were monitored by investigating the luminescence properties of EuL-PMMA. Detailed photoluminescence studies showed insights into the non-radiative rates and improved quantum yields (Q_Eu = 23%) from Eu(III). Furthermore, the higher values of Judd–Ofelt parameters Ω₂ and Ω₄ indicate strong hydrogen bonding interactions between L and PMMA. Nevertheless, these significant optical properties enable LnL-PMMA polymeric materials as colored phosphors for the design of opto-electronic devices. Full article

Hydrochloric acid is conventionally used to pre-hydrolyse starch before periodate oxidation into dialdehyde starch (DAS), which may generate chloride-containing waste. This study proposes a sustainable one-step hydrolysis–oxidation route using acetic acid, a biodegradable organic acid, evaluating reaction time (24–72 h) to maximise aldehyde content while minimising acid hazard. Acetic-acid-derived DAS (24 h) achieved a significantly higher aldehyde content than the HCl route (59.57 ± 0.55% vs. 49.91 ± 1.00%; p < 0.001). This DAS was applied as a covalent crosslinker in chitosan/poly(vinyl alcohol) films loaded with Artemisia herba-alba extract, benchmarked against a non-crosslinked film. Crosslinking increased tensile strength (67.1 vs. 51.5 MPa) and crystallinity (40.83% vs. 17.04%), reduced porosity, and slowed extract release in phosphate-buffered saline (27.5% vs. 41.9% at 168 h; Weibull model, Adj. R² ≥ 0.97) while preserving predominantly Fickian diffusion. Despite releasing less extract, the crosslinked film retained significantly higher DPPH radical-scavenging activity, consistent with hemiacetal interactions between residual aldehydes and extract phenolics. Antibacterial testing against six clinical strains suggested that crosslinking modulates rather than suppresses activity. These findings support acetic-acid-mediated DAS synthesis as a low-hazard, waste-reducing route toward bioactive, controlled-release biopolymer films as promising candidates for future biomedical or active-packaging applications. Full article

Thermochromic wood coatings hold promising application prospects, yet conventional thermochromic microcapsules are limited by monotonous color transitions and non-environmentally friendly wall materials. In this study, two formaldehyde-free thermochromic microcapsules were prepared via spray drying using crystal violet lactone (CVL) and bisphenol A (BPA) as the core system, with chitosan–syringaldehyde (SA-MCs, decyl alcohol as solvent, Schiff base crosslinking) and chitosan–gum Arabic (GA-MCs, lauryl alcohol as solvent, electrostatic complex coacervation) as the wall materials, respectively. These microcapsules were incorporated into basswood ultraviolet (UV) coatings at mass fractions of 1%, 3%, 5%, 7%, and 9%. With increasing microcapsule content, the gloss of both coatings decreased progressively, roughness increased gradually, and the color-changing amplitude, expressed as the color difference (ΔE), was continuously enhanced. At 9% addition, the SA-MC coating exhibited a moderate transition from light yellow to yellow-green (ΔE = 7.2), while the GA-MC coating displayed a dramatic reversible change from deep blue to light gray (ΔE = 42.4), both with good reversibility. In terms of mechanical properties, SA-MCs exhibited higher hardness, both systems achieved an impact resistance grade of 3, and GA-MCs demonstrated superior adhesion. After 24 h of short-term UV accelerated aging, GA-MCs still maintained a higher thermochromic response, albeit with more severe gloss loss. In summary, GA-MCs are superior in color-changing amplitude and adhesion, while SA-MCs offer advantages in gloss retention and hardness, providing a reference for material selection in the application of smart wood finishing. Full article

Coordination compounds with transition metals, especially of molybdenum, are promising cytoprotective agents. In this work, we analyzed the changes in HT-22 cell viability under the influence of molybdenum(VI) Schiff base complexes per se or in cellular injury induced by hydrogen peroxide (annexin V and propidium iodine staining assay). The results allowed to identify the most active compound with dioxidomolybdenum(VI) ion coordinated to Schiff base derived from 1S,2S-(+)-2-amino-1-(4-nitrophenyl)-1,3-propanediol and 5-methoxysalicylaldehyde, protecting the cells and possessing low cytotoxicity. We addressed a range of active concentrations (statistically significant effect from 5 µM to 50 µM) and the temporal characteristics of the effect (which is evident in 1-h preincubation regimen or adding the compound 1 h after hydrogen peroxide). Importantly, the effect was present at different levels of glucose in the medium and in cellular injury induced by glutamate. Less pronounced protective effect was seen in SH-SY5Y cells on the model of hydrogen peroxide-induced (but not in glutamate-induced) cytotoxicity. Among the possible mechanisms of cytoprotective activity, there is a direct interaction with hydrogen peroxide (measured by cyclic voltammetry), decrease in reactive oxygen species generation (DCFH-DA assay in HT-22 cells) and maintenance of catalase activity (assessed in lysates of HT-22 cells on the model of hydrogen peroxide-induced injury). Full article

In biofuel cells using laccase, the electron supply to the type 1 (T1) site is inefficient, constituting a major bottleneck for the overall reaction. To solve this problem, the use of mediator molecules that mediate electron transfer is being studied. Furthermore, lignin is known to be oxidized by laccase and can donate electrons, which indicates the potential application of this reaction in biofuel cells. Therefore, in this study, docking calculations were performed to clarify the interactions between a copper(II) complex mediator and laccase. At the same time, a copper complex mediator was selected, and cyclic voltammetry (CV) measurements were performed to evaluate its electrochemical properties. In the CV measurements, the differences in current responses with and without the mediator and lignin (an oxidized substrate of laccase) were compared. As a result, based on the docking calculations, it was proposed that the synthesized copper complex mediator binds relatively strongly to laccase. Moreover, CV measurements confirmed that the current tended to increase upon the addition of the mediator and/or lignin. This current enhancement explicitly demonstrates the efficient electron-providing effect of the mediator and lignin to the laccase-based system. Full article

Traditional fluorescent probes often exhibit compromised response and specificity due to poor adaptability to varying polar environments. Herein, we present the development of a robust Fe³⁺-specific small-molecule sensor by linking a tetraphenylsilole derivative and rhodamine 6G hydrazide via a Schiff-base π bridge to form a fluorescent donor–acceptor system. The dispersed silole moiety serves as dark donor, while the aggregated state of silole converts into emissive donor. Upon selective binding with Fe³⁺, the molecules are found to undergo fluorescence resonance energy transfer (FRET) and dark resonance energy transfer (DRET) to rhodamine moiety in a polarity-dependent manner. Hence, fluorescence quantitation of Fe³⁺ in both high-organic (>70%) and water-rich solutions (>70%) is successfully achieved with detection limits of 0.083 μM and 0.28 μM, respectively. Further, ratiometric intracellular imaging of Fe³⁺ is demonstrated using the probe. This sensing strategy can offer a promising avenue for the development of polarity-adaptive fluorescent probes targeting other metal ions in complex biological and environmental matrices. Full article

The coordination chemistry of “salen-type” Schiff bases with the uranyl ion, trans-{U^VIO₂}²⁺, attracts the interest of several inorganic chemistry groups worldwide for a variety of reasons. The full synthetic investigation of the {UO₂}²⁺/H₂L reaction system, where H₂L is bis(2-hydroxyacetophenone)ethylenediamine, has provided access to complexes [UO₂(L)(EtOH)] (1) and [UO₂(L)(DMF)] (2) in moderate to good yields. The molecular structures of the two complexes are similar. The U^VI atoms are bonded to five oxygen and two nitrogen atoms in a distorted pentagonal bipyramidal geometry. The two uranyl oxo(or oxido) atoms occupy the axial positions, and the {O=U=O}²⁺ moiety is almost linear. The equatorial donor atoms are the two oxygens and the two nitrogens from the tetradentate chelating (1.1111 using Harris notation) L²⁻ ligand, and the oxygen atom of the coordinated solvent molecule. H-bonded dimers of 1 exist in its crystal structure. The complexes were fully studied in the solid state by IR, Raman, UV/Vis (diffuse reflectance) and emission spectroscopies, and the data are discussed in terms of the known structural data of the complexes and the coordination modes of the ligands. The structures of the complexes persist in solution as evidenced by NMR (¹H, ¹³C{¹H}) and UV/Vis spectroscopies, as well as by molar conductivity data. Complexes 1 and 2 exhibit moderate photocatalytic activity towards the degradation of the model organic dye methylene blue under continuous UV irradiation in aqueous media. The reaction kinetics were fitted using the Langmuir-Hinshelwood pseudo-first-order model. Combined IR and powder X-ray diffraction data show that the photocatalyst 1 remains unchanged after the photocatalytic experiment, whereas 2 undergoes DMF leaching. Based on literature reports, a simplified single-electron transfer mechanism has been proposed for the photocatalytic activity. Full article

Reactive aldehydes—formaldehyde (FA), malondialdehyde (MDA), 4-hydroxynonenal (4-HNE), and acrolein—occupy a central role in epigenetic regulation, lipid peroxidation, ferroptosis, and cardiovascular disease, yet their transient nature and low intracellular concentrations have long made them difficult to quantify in living systems. Over the past decade, reaction-based small-molecule fluorescent probes have emerged as the principal tool for addressing this challenge, and this review provides a systematic account of that progress. We compare the six main conjugation chemistries that underlie current probe design—2-aza-Cope/Mannich cascade, hydrazone/oxime formation, Michael addition, Schiff base condensation, and 2-aminothiophenol cyclization—alongside the three photophysical strategies used to convert these reactions into quantitative signals: intensity turn-on, ratiometric dual-emission, and fluorescence lifetime imaging (FLIM). Attention is given to advances reported between 2020 and 2025, including organelle-targeted ratiometric formaldehyde sensors (MitoRFAP-2, NucRFAP-2), the first ratiometric acrolein probe for visualizing ferroptosis, lysosome-targeted malondialdehyde reporters for atherosclerosis staging, and near-infrared-compatible platforms validated in three-dimensional organoids and in vivo models. This review also critically examines the limitations that continue to constrain the field, including insufficient selectivity testing under physiologically relevant conditions, the pH-dependence of hydrazone equilibria, the frequently overlooked distinction between probes that report free aldehyde concentration and those that report ALDH enzyme activity, and the continued absence of reversible, real-time sensors. Closing these gaps will determine whether aldehyde imaging grows from a set of smart probes into a quantitative, widely trusted platform for studying redox and carbonyl biology in living systems. Reaching that point will depend on three criteria: better NIR fluorophores, effective bioconjugation chemistry, and machine-learning tools that guide probe design. Full article

Background/Objectives: Tissue bio-adhesives have gained significant attention as efficient alternatives to conventional wound closures, which are often hindered by insufficient adhesion and poor biocompatibility. Methods: Inspired by nature’s robust wet-adhesion strategies that use dynamic covalent interactions, we have reported a facilely fabricated hydrogel bio-adhesive based on lactobionic acid-conjugated polyethylenimine (LA-PEI) and oxidized dextran (ODex) via Schiff base linkages. Results: The prepared hydrogels exhibited three-dimensional interconnected porous networks, regulated swelling ratios, typical viscoelasticity, shear-thinning behavior, and self-healing ability. Notably, the swelling ratios of the hydrogels depended on composition, and OLP11 displayed the highest swelling ratio of over 1500%. The hydrogel bio-adhesives exhibited strong adhesion to various surfaces, including glass, metal, plastic, rubber, and wood, as well as to different chicken organs, including the heart, liver, spleen, and stomach. Furthermore, the hydrogels exhibited excellent ABTS radical-scavenging activity, effective intracellular reactive oxygen species (ROS) scavenging, and good hemocompatibility, with hemolysis ratios of all hydrogels close to 0%, below the threshold of 5%. After culturing with NIH 3T3 fibroblasts, the hydrogels demonstrated good cytocompatibility and promoted cell proliferation, with cell viabilities on day 3 reaching over 90%. Conclusions: This design yields multifunctional hydrogel bio-adhesives, showing strong promise for wound care and tissue repair applications. Full article

Isolating rhenium and molybdenum selectively from multicomponent acidic hydrometallurgical solutions remains problematic because of the abundance of competing cations and the low concentration of target oxoanions. This study investigates the sorption of Re(VII) and Mo(VI) oxoanions by an interpolymer system (IPS) comprising a cellulose–polyethyleneimine–glutaraldehyde (Cellulose-PEI-GA) weak-base anion exchanger and a sulfonated styrene–divinylbenzene cation-exchange resin (Lewatit MonoPlus SP112H), operating as spatially separated but solution-coupled phases. The industrial feed, a sulfuric acid leach liquor from electrostatic precipitator dust at the Zhezkazgan copper smelter, Kazakhstan (pH 1.25), was pretreated by liquid–liquid extraction with a trialkylamine-2-ethylhexanol–kerosene system followed by ammonia stripping to give an alkaline re-extract (pH 11.98) used for sorption. At the optimal 1:1 mass ratio of the two components (3:3), the IPS achieved a rhenium recovery of 77.7% (Kd = 3678 mL g⁻¹, q = 4.51 mg g⁻¹) against a markedly lower molybdenum recovery of 24.0% (Kd = 333 mL g⁻¹), giving a Re/Mo separation factor β of 8.8–15.5 across the studied compositions; this uptake exceeded the value predicted from the individual sorbents by a factor of ~2.6, indicating a cooperative rather than purely additive effect. Sorption kinetics (pseudo-first-order, pseudo-second-order and Elovich models) and diffusion mechanisms (Weber–Morris and Boyd models) were consistent with mixed film- and intraparticle-diffusion control. Desorption with hydrochloric acid recovered 91.4% of the sorbed rhenium and 89.1% of the molybdenum, and FTIR, TGA, and BET analyses (surface area increasing from 1.93 to 8.62 m² g⁻¹ for the cellulose component and from 7.21 to 8.46 m² g⁻¹ for the resin) confirmed sorbate-induced textural and compositional changes consistent with the proposed complementary anion-/cation-exchange mechanism. Full article

This study developed novel immunostimulatory hydrogels composed of aldehyde-modified Arnebia euchroma polysaccharide (oxidized ARP, O-ARP) and gelatin (GE) for oligonucleotide delivery. Structural characterization of three O-ARP derivatives with varying degrees of oxidation confirmed reduced molecular weight, a preserved yet altered molar ratio of monosaccharide composition, and triple-helical conformation. Hydrogels (GE-O1, GE-O2, GE-O3) were formed via a Schiff base reaction between aldehyde and amino groups. Molecular dynamics simulations showed that O-ARP and gelatin can form a stable three-dimensional (3D) network via hydrogen bonding and van der Waals interactions. In vitro studies demonstrated that both the O1-ARP derivative and GE-O1 hydrogel significantly improved RAW 264.7 macrophage viability, phagocytosis, NO production, and pro-inflammatory cytokine secretion, including IL-6, IL-1β, and TNF-α. The cationic GE-O1 hydrogel efficiently loaded anionic CpG oligonucleotides (CpG-ODN 1862) via electrostatic interaction, forming GE-O1-CpG complexes and promoting cellular uptake. Importantly, the GE-O1-CpG complex exhibited superior immunomodulatory effects compared with either GE-O1 or CpG alone, indicating a synergistic dual immunostimulatory response. In vivo studies confirmed the biosafety of GE-O1-CpG. Using OVA as a model antigen, GE-O1-CpG/OVA enhanced both humoral and cellular immune responses. These findings support GE-O1-CpG hydrogels as potential system for combined immunomodulation and nucleotide delivery. Full article

The novel complex [Fe^III(HL)(L)]·2dmf (1) was successfully synthesized by reacting iron chloride with dimethylformamide solution of the Schiff base ligand (H₂L). The ligand was prepared in situ through the condensation of 5-bromo-salicylaldehyde and benzhydrazide. The compound 1 was investigated by single crystal X-ray diffraction, IR spectroscopy, CASSCF/NEVPT2 and DFT theoretical calculations, revealing the high-spin (S = 5/2) state of Fe(III). The Hirshfeld Atom Refinement (HAR) of the crystal structure confirmed the sextet ground spin state of 1 through the comparison of R-factors and Hirshfeld deformation maps of the structures refined assuming high, indeterminate (S = 3/2) and low (S = 1/2) ground spin states. A series of basis sets and DFT functionals was screened, indicating that in most cases the combinations allow the correct determination of the ground state of 1. The def2-SVP double-zeta basis set combined with the GGA (Generalized Gradient Approximation) functional such as PBE or BP86 was found to be a sufficiently precise low-cost computational level. While further investigation is necessary, the results of the work tentatively suggest that the HAR could be successfully used for determination of the ground spin state of Fe(III) complexes even in the case of regular quality X-ray structures. Full article

Reintroducing crop straw into soil boosts organic matter, but natural crop straw usually shows low nutrient content. To enhance the water absorption rate of a certain thin sheet-shaped iron-containing material, a technical approach combining ball milling, the Mannich reaction, Schiff’s base cross-linking, emulsion separation, and solid–liquid adsorption was attempted to prepare iron-containing microspheres using sodium alginate and rice straw as raw materials. This approach increased the content of the trace nutrient iron and improved the water absorption rate. The results indicated that the iron-containing microspheres exhibit a diameter ranging from approximately 15 μm, an iron content of 10.44%, and a water absorption rate of 501.76%. The release rates of iron and nitrogen in soil and water within the first day were all below 15%, while the release rates after 30 days in soil were 61.8% for iron and 44.32% for nitrogen, and the corresponding rates in water were 73.1% for iron and 63.88% for nitrogen. The water absorption capacity of the iron-containing microspheres showed a trend associated with particle size and pore structure parameters. The development of iron-containing microspheres has expanded the preparation technology for semi-interpenetrating structure type sustained-release materials, and holds the potential for further development into slow-release fertilizers. Full article

A tetraphenylethylene-based salen-type Schiff base ligand and its Fe(III) coordination complex were synthesized and characterized using spectroscopic, electrochemical, mass spectrometric, and single-crystal X-ray diffraction techniques. The ligand features an N₂O₂ donor set and was obtained via Schiff base condensation with ethylenediamine, while reaction with FeCl₃ afforded a di-μ-phenoxo-bridged dinuclear Fe(III) complex under mild conditions. Unlike previously reported Fe(III)-salen electrochromic systems, which are predominantly mononuclear and exhibit ligand-centered redox processes with limited modulation of intraligand electronic communication, the present system incorporates a rigid tetraphenylethylene scaffold and forms a centrosymmetric di-μ-phenoxo-bridged Fe(III) dimer. This structural motif enables coordination-induced electronic coupling between phenolate units, resulting in a distinct splitting of ligand-centered oxidation processes. Single-crystal X-ray diffraction confirmed a di-μ-phenoxo-bridged Fe(III) dimer with distorted octahedral geometry. Electrochemical studies show a quasi-reversible ligand-centered oxidation in the free ligand, which splits into two separate redox events upon complexation, indicating the emergence of electronically non-equivalent redox sites. Spectroelectrochemical analysis reveals the formation of phenoxyl radical species accompanied by ligand-centered intervalence charge–transfer transitions and the appearance of a near-infrared absorption band upon oxidation. A reversible color change from red to blue is observed, reflecting redox-driven modulation of the electronic structure. Overall, this work demonstrates that incorporation of a tetraphenylethylene-based salen framework and formation of a di-μ-phenoxo-bridged Fe(III) dimer enables coordination-triggered intraligand electronic communication, leading to fundamentally different redox behavior compared to previously reported Fe(III)-salen electrochromic complexes, while no reversible metal-centered redox processes were detected within the experimentally investigated potential window. Full article

We investigate the ultrafast dynamics of a visible-light-driven salicylaldehyde Schiff base-functionalized molecular motor using non-adiabatic molecular dynamics (NAMD) at the orthogonalization-corrected method 2 and the multireference configuration interaction (OM2/MRCI) level. Results reveal a dynamic competitive interplay between E → Z photoisomerization and excited-state intramolecular proton transfer (ESIPT). Importantly, we reveal a direct coupling mechanism between double-bond rotation and proton transfer: within a critical 500–900 fs window, ESIPT transiently stalls rotor rotation while modulating the central double-bond order. The S₁ state lifetime is ~1677 fs. Time-resolved fluorescence analysis further predicts rapid fluorescence quenching within ~37 fs accompanied by a pronounced spectral red-shift, indicating that the system quickly enters a dark state with negligible oscillator strength. This study provides atomistic insights into the relaxation pathways of visible-light-driven motors, offering a theoretical basis for designing efficient long-wavelength responsive molecular machines. Full article