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A series of isostructural early actinide AnIV complexes was synthesized in order to investigate the influence of a conjugated framework in the ligand backbone on An bonding. Therefore, the AnIV complexes [An(pyrophen)2] (An = Th, U, Np, and Pu) with the pure N donor ligand bis(2-pyrrolecarbonylaldehyde)-o-phenylenediamine referred to as pyrophen, were synthesized and characterized. Solid state analysis via single-crystal X-ray diffraction (SC-XRD) reveals two sets of ligands binding in an almost orthogonal arrangement to the actinide center. For the larger actinides Th and U, the coordination sphere allows for additional coordination by a solvent molecule. Nuclear magnetic resonance spectroscopy (NMR) studies show the presence of highly symmetrical complexes in solution in good agreement with the solvent-free solid structures. While SC-XRD suggests mainly ionic binding, an analysis of paramagnetic NMR contributions and quantum chemical bond analysis hint towards significant covalency in the U, Np, and Pu compounds. This series of An complexes allowed for a thorough structural and theoretical comparison of a conjugated system to a closely related N-donor ligand (pyren)[1], as well as to the mixed N,O Schiff base ligands salophen (conjugated) and salen (non-conjugated).

IR spectra NMR spectra QCC results SC-XRD results PCS cone calculations

The dynamic interplay between cells and their native extracellular matrix (ECM) influences cellular behavior, imposing a challenge in biomaterial design. Dynamic covalent hydrogels are viscoelastic and show self-healing ability, making them a potential scaffold for recapitulating native ECM properties. We aimed to implement kinetically and thermodynamically distinct crosslinkers to prepare self-healing dynamic hydrogels to explore the arising properties and their effects on cellular behavior. To do so, aldehyde-substituted hyaluronic acid (HA) was synthesized to generate imine, hydrazone, and oxime crosslinked dynamic covalent hydrogels. Differences in equilibrium constants of these bonds yielded distinct properties including stiffness, stress relaxation, and self-healing ability. The effects of degree of substitution (DS), polymer concentration, crosslinker to aldehyde ratio, and crosslinker functionality on hydrogel properties were evaluated. The self-healing ability of hydrogels was investigated on samples of the same and different crosslinkers and DS to obtain hydrogels with gradient properties. Subsequently, human dermal fibroblasts were cultured in 2D and 3D to assess the cellular response considering the dynamic properties of the hydrogels. Moreover, assessing cell spreading and morphology on hydrogels having similar modulus but different stress relaxation rates showed the effects of matrix viscoelasticity with higher cell spreading in slower relaxing hydrogels., QC 20240520

The present study aimed to prepare and then evaluate the tetra and coordinated Bismuth (III) complexes [BiCl2 (L)] (LH = N, O donor Schiff base employed by the condensation of 1-acetyl-2-naphthol and 2-acetyl-1-naphthol using sulpha drugs as ligand) were derived by the reaction of bismuth (III) trichloride and sodium salt of an N, O donor Schiff base ligand and characterized. The authenticity of all the synthesized ligands and their Bi (III) complexes had been identified by microanalysis, various spectroscopic techniques like FT-IR, 1H NMR, and elemental analysis. The spectral evidence of the complexes has revealed the bidentate complexing nature of the Schiff base through phenolic oxygen and azomethine nitrogen atoms. The Schiff base ligand and Bismuth (III) complexes were assessed for antimicrobial activity. Assessment of antimicrobial activity against Gram-negative & Gram-positive bacteria and fungi has demonstrated that the complex (III) was more active than the Schiff base.

In this study, hydrogels were produced using a Schiff base reaction between two hyaluronic acid derivatives: one containing aldehyde groups (HA-Ald) and the other holding a diethylenetriamine with terminal amino groups (HA-DETA). The DETA portion promotes the in situ growth, complexation, and stabilization of silver nanoparticles (AgNPs), eliminating the need for external reducing agents. The reaction between HA-DETA and HA-Ald leads to the formation of imine bonds, which results in dynamically pH-responsive cross-linking. While the DETA capping ability helped in embedding the AgNPs, the on/off pH environmental responsivity of the hydrogel allows for a controlled and on-demand release of the drug, mainly when bacterial infections cause pH variation of the wound bed. The injectable hydrogels resulted in being highly compatible in contact with blood red cells, fibroblasts, and keratinocytes and capable of having a proliferative effect on an in vitro wound scratch model. The pH-responsive hydrogels showed proper antibacterial activity againstPseudomonas aeruginosaandStaphylococcus aureus, common bacterial strains presented in wound infections. Finally, in vivo wound model studies demonstrated an overall speeding up in the wound healing rate and advanced wound conditions in the experimental group treated with the hydrogels compared to control samples.

Schiff bases (SBs) are important ligands in coordination chemistry due to their unique structural properties. Their ability to form complexes with metal ions has been exploited for the environmental detection of emerging water contaminants. In this work, we evaluated the complexation ability of three newly proposed SBs, 1-3, by complete conformational analysis, using a combination of Molecular Dynamics and Density Functional Theory studies, to understand their ability to coordinate toxic heavy metal (HMs) ions. From this study, it emerges that all the ligands present geometries that make them suitable to complex HMs through the N-imino moieties or, in the case of 3, with the support of the oxygen atoms of the ethylene diether chain. In particular, this ligand shows the most promising coordination behavior, particularly with Pb2+.

Bio-based plastics potentially have several positive impacts on the environment; however, in order to make a real difference, they need to have managed and sustainable end of life. This means they should from the start be designed for chemical, mechanical, and/or organic (biological) recycling. Development of energy-efficient and selective chemical recycling processes is a necessary part in reaching truly circular plastic flows. Polyesters are generally well suited for chemical recycling due to the presence of reversible ester bonds. Utilization of dynamic covalent chemistry to include a second, even more easily reversed bond, such as Schiff base (SB, imine bond), could further facilitate chemical recycling, enabling depolymerization back to monomeric products under mild conditions. Here, we present the synthesis of three vanillin-derived SB monomers SBM1, SBM2, and SBM3 and the corresponding polymers SBP3a-b, SBP4a-b, and SBP5a-b. Three different diamines and two potentially bio-sourced diesters were utilized to yield altogether six different polyester-imines with different aliphatic/aromatic contents. All the obtained SB-based polyesters were thermally stable at ∼290-330 °C and had a high char yield during the pyrolysis, which may indicate inherent flame resistance. All the polyesters were amorphous with glass transition temperatures from 36 to 76 °C. The chemical recyclability and hydrolytic degradation of the synthesized polyesters was evaluated by using real-time 1H NMR spectroscopy. Finally, the susceptibility of the synthesized polyester-imines to enzymatic degradation by PETase was demonstrated. The experimental results were further supported by induced-fit docking experiments to theoretically evaluate the potential productive binding of the produced polyester-imines and intermediates thereof to the active site of PETase., QC 20230629

The influence of the solvent in the reaction of dysprosium(III) chloride hydrate with the N3O2 ligand H2L (2,6-bis(2-hydroxyphenyliminomethyl)pyridine) was studied To this end, the new mononuclear chloride complex [Dy(L)Cl(H2O)2] (1) was isolated in absolute ethanol as solvent, without any evidence of the hydrolysis of the ligand. This clearly contrasts with previous results, where a similar reaction in methanol proceeds with the partial hydrolysis of the Schiff base, and the formation of a new hemiacetal donor to yield [Dy(HL’)2)][Dy(L)(Cl2)] (H2L’ = (6-(2- hydroxyphenyliminomethyl)-2-methoxyhydroxymethyl)pyridine). The single crystal X-ray structure of the chloride complex 1 shows that the DyIII ion is octacoordinated in a highly distorted N3O4Cl environment between triangular dodecahedral and biaugmented trigonal prisms. The full magnetic characterisation of 1 shows that it presents field-induced single ion magnet behaviour, with a thermal energy barrier Ueff of 113.5 K, which is the highest among dysprosium complexes derived from H2L.

Mn (II) complexes were synthesized with the Schiff base ligand obtained by the condensation of sulfathiazole with 4-diethylaminosalicyaldehyde/Salicyaldehyde. Their characterization was performed by elemental analysis, molar conductance, melting points, magnetic susceptibility, infrared, and UV–Vis spectral analysis. The results suggest that the Schiff bases and their complex are synthesized in excellent yield, molar conductance studies on the complexes indicated they were non-electrolytic. The IR data indicated that the Schiff base ligand is tridentate coordinated to the metallic ion with two N atoms from the azomethine group and thiazole ring and one O atom from the phenolic group. The electronic spectral study showed octahedral geometry for all the complexes which are further supported by magnetic moment values. The ligand and its complexes were screened against four bacterial and two fungal strains using the disk diffusion method. The antimicrobial evaluation results revealed that the metal (II) complexes exhibited higher antimicrobial activity than the free Schiff base ligand. The ADMET and drug-likeness studies of the synthesized ligands indicated that the Schiff base ligands fulfill Lipinski’s, Ghoose, Veber, Egan, and Mugge rules but the complexes showed some deviations. They also displayed low toxicity levels.

Fe(III) and Mn(II) complexes with condensation product of thiosemicarbazide and 2-acetylthiazole (HL1, (E)-2-(1-(thiazol-2-yl)ethylidene)hydrazine-1-carbothioamide) have been synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy, and elemental analysis. In both complexes, the thiosemicarbazone ligand is coordinated in deprotonated form through the NNS donor set of atoms. However, while Fe(III) complex is in the doublet ground state with distorted octahedral geometry, the coordination environment around Mn(II) is distorted trigonal-prismatic, and the sextet state is found to be the ground state. DFT calculations were performed to rationalize spin state preferences, and continuous shape measure describes the deviation from ideal six-coordinated polyhedral geometries in the ground and excited states. Antimicrobial activity (against a panel of Gram-negative and Gram-positive bacteria, two yeast, and one fungal strain), brine shrimp assay, and DPPH radical scavenging activity of both complexes were evaluated, and these results relate to the electronic structure of the complexes.

In recent decades, the use of thermoset epoxy resins (ER) has spread to countless applications due to their mechanical properties, heat resistance and stability. However, these ERs are neither biodegradable nor recyclable due to their permanent crosslinked networks and usually, they are synthesized from fossil and toxic precursors. Therefore, reducing its consumption is of vital importance to the environment. On the one hand, the solution to the recyclability problems of epoxy resins can be achieved through the use of vitrimers, which have thermoset properties and can be recycled as thermoplastic materials. On the other hand, vitrimers can be made from natural sources, reducing their toxicity. In this work, a sustainable epoxy vitrimer has been efficiently synthesized, VESOV, by curing epoxidized soybean oil (ESO) with a new vanillin-derived Schiff base (VSB) dynamic hardener, aliphatic diamine (1,4-butanediamine, BDA) and using 1,2-dimethylimidazole (DMI) as an accelerator. Likewise, using the same synthesized VSB agent, a commercial epoxy resin has also been cured and characterized as ESO. Finally, different percentages (30, 50 and 70 wt%) of the same ER have been included in the formulation of VESOV, demonstrating that only including 30 wt% of ER in the formulation is able to improve the thermo-mechanical properties, maintaining the VESOV’s inherent reprocessability or recyclability. In short, this is the first approach to achieve a new material that can be postulated in the future as a replacement for current commercial epoxy resins, although it still requires a minimum percentage of RE in the formulation, it makes it possible to recycle the material while maintaining good mechanical properties.

Fe(III) and Mn(II) complexes with condensation product of thiosemicarbazide and 2-acetylthiazole (HL1, (E)-2-(1-(thiazol-2-yl)ethylidene)hydrazine-1-carbothioamide) have been synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy, and elemental analysis. In both complexes, the thiosemicarbazone ligand is coordinated in deprotonated form through the NNS donor set of atoms. However, while Fe(III) complex is in the doublet ground state with distorted octahedral geometry, the coordination environment around Mn(II) is distorted trigonal-prismatic, and the sextet state is found to be the ground state. DFT calculations were performed to rationalize spin state preferences, and continuous shape measure describes the deviation from ideal six-coordinated polyhedral geometries in the ground and excited states. Antimicrobial activity (against a panel of Gram-negative and Gram-positive bacteria, two yeast, and one fungal strain), brine shrimp assay, and DPPH radical scavenging activity of both complexes were evaluated, and these results relate to the electronic structure of the complexes., Additional crystallographic and computational results, and the Cartesian coordinates of all DFT optimized structures

In this study, 2,5-dimethyl-4-((4-nitrobenzylidene) amino) phenol (A1), N,N'-([1,1'-biphenyl]-4,4'-diyl)bis(1-(2,4-dimethoxyphenyl)methanimine (A2) and 4,4'-(([1,1'-biphenyl]-4,4'-diylbis(azaneylylidene))bis (methaneylylidene))bis(2-methoxyphenol) (A3) were synthesised. Analytical studies were then carried on (A1), (A2) and (A3); the results of the solvent effect were displayed that the best solubility was in ethanol and DMSO of each, which is due to the fact that the effect of the dielectric constant is the main factor that can control the shift of the absorption beaks. The results were also indicated, that there is a slight deviation from the linear relationship in (A3) that may have related to the hydrogen bond between this base and the solvent. However, the results of the pH effect of (A1), (A2) and (A3) in a range of buffer solution were gave two isopiestic points just in (A3). Due to the ionization constant (pKa) and the protonation constant (pKp) were calculated by using the half height method. Further, the results were indicated the existence of the equilibrium schemes of which displays the suggested ionization of (A3) in acidic and basic medium. Further, the effect of the prepared Schiff bases (A1, A2, and A3) were studied on breast cancer cells type MCF-7 using five different concentrations of each. The results were showed high inhibition activities of each especially at high concentration, due recommend these bases as novel anti-cancer drugs.

A new metal-free macrocyclic Schiff base ligand bearing two metal cavities incorporated with two sets of N3O2 donor atoms derived from 2, 6-diaminopyridine and isatine was synthesized. The new ligand was used to prepare homo and hetero binuclear macrocyclic Schiff base complexes with Ni (II), Cu (II), ZrO (II) and Ba (II) metal ions. The ligand and metal complexes were characterized using Fourier transform infrared (FT-IR), UV–vis, mass spectroscopy, elemental analysis (CHN), thermo gravimetric analysis (TGA), magnetic susceptibility, and molar conductivity measurements. The DFT calculations using the B3LYP functional method have been applied to obtain the geometry and electronic properties of the ligand and its metal complexes to support the experimental data. To describe the reactivity of the title molecules, the HOMO and LUMO levels and Mulliken atomic charges were determined.

Six derivatives of novel triazoles were produced from some substituted benzoic acid with thiocarbazide via method of grinding. The produced Chemicals were described via 1HNMR, IR, and 13CNMR spectra examinations. Produced derivatives of C2H3N3 were examined and assessed as reducing of corrosion in 0.5 M HCl for low-C steel utilizing procedure of losing weight. It was noticed that such chemicals had an encouraging act as reducer counter to mild steel corrosion of in solution being acidic. Reducing of maximum action was assessed at various concentrations and temperature of effector. Competence of corrosion reducer surpassed 96%. The exceptional action was due to inhibitor films adsorption development on surfacing steel. Reducing adsorption on surface of steel tracked Langmuir adsorption isotherm (LAI). The results were long-established BY theoretical calculations of quantum chemistry.

Tannery industries are one of the extensive industrial activities which are the major source of chromium contamination in the environment. Chromium contamination has been an increasing threat to the environment and human health. Therefore, the removal of chromium ions is necessary to save human society. This study is oriented toward the preparation of a new triazole Schiff base derivatives for the remediation of chromium ions. 4,4′-((1E)-1,2-bis ((1H-1,2,4-triazol-3-yl) imino)ethane-1,2-diyl) diphenol was prepared by the interaction between 3-Amino-1H-1,2,4-triazole and 4,4′-Dihydroxybenzil. Then, the produced Schiff base underwent a phosphorylation reaction to produce the adsorbent (TIHP), which confirmed its structure via the different tools FTIR, TGA, 1HNMR, 13CNMR, GC-MS, and Phosphorus-31 nuclear magnetic resonance (31P-NMR). The newly synthesized adsorbent (TIHP) was used to remove chromium oxyanions (Cr(VI)) from an aqueous solution. The batch technique was used to test many controlling factors, including the pH of the working aqueous solution, the amount of adsorbent dose, the initial concentration of Cr(VI), the interaction time, and the temperature. The desorption behaviour of Cr(VI) changes when it is exposed to the suggested foreign ions. The maximum adsorption capacity for Cr(VI) adsorption on the new adsorbent was 307.07 mg/g at room temperature. Freundlich’s isotherm model fits the adsorption isotherms perfectly. The kinetic results were well-constrained by the pseudo-second-order equation. The thermodynamic studies establish that the adsorption type was exothermic and naturally spontaneous. © 2022 by the authors.

Turning thermosets into fully sustainable materials requires utilization of biobased raw materials and design for easy recyclability. Here, dynamic covalent chemistry for fabrication of covalent adaptable networks (CANs) could be an enabling tool. CAN thermosets ideally combine the positive material properties of thermosets with thermal recyclability of linear thermoplastics. Among the dynamic covalent bonds, imine bond, also called Schiff base, can participate in both dissociative and associative pathways. This induces potential for chemical recyclability, thermal reprocessability and self-healing. This review presents an overview of the current research front of biobased thermosets fabricated by Schiff base chemistry. The discussed materials are categorized on the basis of the employed biobased components. The chemical approaches for the synthesis and curing of the resins, as well as the resulting properties and recyclability of the obtained thermosets are described and discussed. Finally, challenges and future perspectives are briefly summarized., QC 20230612

We studied the interaction of Cu2+ ions and CuO nanoparticles with the fluorescent Schiff base ligand H3L, which derives from the condensation of 4-formyl-3-hydroxybenzoic acid with N-(2-aminobenzyl)-5-(dimethylamino)naphthalene-1-sulfonamide (DsA). A detailed assignment of the most significant bands of the electronic and infrared spectra of H3L and DsA was performed using DFT methods, based on both crystal structures. The affinity of H3L to react with Cu2+ ions in solution (KB = 9.01 103 L mol-1) is similar to that found for the Cu2+ ions present on the surface of CuO NPs (KB = 9.84 103 L mol-1). Fluorescence spectroscopic measurements suggest five binding sites for H3L on the surface of the CuO NPs used. The µ-XRF analysis indicates that a polycrystalline sample of CuO-H3L NPs contains 15:1 Cu:S molar ratio (CuO:H3L). ATR-FTIR spectroscopy, supported by DFT calculations, showed that the HL2- (as a phenolate and sulfonamide anion) is coordinated to superficial Cu2+ ions of the CuO NPs through their azomethine, sulphonamide, and phenolic groups. A solution of H3L (126 ppb) shows sensitive responses to CuO NPs, with a limit of detection (LOD) of 330 ppb. The working range for detection of CuO NPs with [H3L] = 126 ppb was 1.1-9.5 ppm. Common metal ions in water, such as Na+, K+, Mg2+, Ca2+, Fe3+, and Al3+ species, do not interfere significantly with the detection of CuO NPs.

The structures of the first two complexes with bidentate coordination of aminoguanidine Schiff base, i.e., 2-acetylpyridine-aminoguanidine (L), are reported. The complex of the formula [Cd2Cl6(HL)2] (1) was obtained in the reaction of warm aqueous solutions of chloride salts of Cd(II), Zn(II) and the ligand, while the reaction of cadmium bromide and the ligand in the presence of deprotonating agent as well as ammonium thiocyanate resulted in the formation of the complex in which Schiff base has both the role of the ligand and the counterion, viz., [HL][Cd(HL)(NCS)2XY]·H2O (2), where X is Cl- or Br-, and Y Br- or SCN-. The complexes were characterized by IR spectroscopy, elemental analysis, conductometric measurements and single crystal X-ray diffraction. The unusual bidentate coordination of the Schiff base lead to significant changes in the geometry of this molecule (from almost planar in free form and as a tridentate ligand to twisted as a bidentate ligand). Besides, in complex 1 relatively rare bridging coordination of Cl- in octahedral Cd(II) is found, while the crystal structure of complex 2 exhibits substitutional disorder, and contains four different anions: [Cd(HL)(NCS)2Br(SCN)]- (ca. 61 %), [Cd(HL)(NCS)2Cl(SCN)]- (ca. 35 %), [Cd(HL)(NCS)2Br2]- (ca. 3 %) and [Cd(HL)(NCS)2ClBr]- (ca. 1 %).

Smart hydrogels based on natural polymers present an opportunity to fabricate responsive scaffolds that provide an immediate and reversible reaction to a given stimulus. Modulation of mechanical characteristics is especially interesting in myocyte cultivation, and can be achieved by magnetically controlled stiffening. Here, hyaluronan hydrogels with carbonyl iron particles as a magnetic filler are prepared in a low-toxicity process. Desired mechanical behaviour is achieved using a combination of two cross-linking routes-dynamic Schiff base linkages and ionic cross-linking. We found that gelation time is greatly affected by polymer chain conformation. This factor can surpass the influence of the number of reactive sites, shortening gelation from 5 h to 20 min. Ionic cross-linking efficiency increased with the number of carboxyl groups and led to the storage modulus reaching 10(3) Pa compared to 10(1) Pa-10(2) Pa for gels cross-linked with only Schiff bases. Furthermore, the ability of magnetic particles to induce significant stiffening of the hydrogel through the magnetorheological effect is confirmed, as a 10(3)-times higher storage modulus is achieved in an external magnetic field of 842 kA.m(-1). Finally, cytotoxicity testing confirms the ability to produce hydrogels that provide over 75% relative cell viability. Therefore, dual cross-linked hyaluronan-based magneto-responsive hydrogels present a potential material for on-demand mechanically tunable scaffolds usable in myocyte cultivation.

The Schiff base ligand H2L has been synthesized by condensation of 2-aminophenol with 3-methyl-1-phenyl-4-formylpyrazol-5-one and reaction between H2L and Ni(OOCR3)2, R = H in 1, –CH3 in 2, Cl in 3, yielded three new tetranuclear Ni(II) complexes. The complexes have been characterized by elemental analysis, IR- and ES-MS spectroscopy. Their structures as well as structure of ligand were determined by single-crystal X-ray diffraction. Compounds 1–3 possesses tetranuclear cubane-like structures containing [Ni4L4(R3COO)2]2 complex anions, which are charge balanced by two triethyl ammonium cations. Furthermore, the crystal structure of the Ni(II) cubane compound containing trichloroacetate bridging ligands, is reported for the first time. Variable temperature magnetic susceptibility measurements revealed interplay between ferromagnetic and antiferromagnetic exchange in the tetranuclear cubane-like compounds 1–3, in which ferromagnetic interactions were enhanced by introducing carboxylate bridging groups. DFT calculations supported the analysis of magnetic data.

In this work we report solvatochromic and luminescent properties of ethyl N-salicylideneglycinate (1), ethyl N-(5-methoxysalicylidene)glycinate (2), ethyl N-(5-bromosalicylidene)glycinate (3), and ethyl N-(5-nitrosalicylidene)glycinate (4) dyes. 1-4 correspond to a class of N-salicylidene aniline derivatives, whose photophysical properties are dictated by the intramolecular proton transfer between the OH-function and the imine N-atom, affording tautomerization between the enol-imine and keto-enamine forms. Photophysical properties of 1-4 were studied in different pure non-polar and (a)protic polar solvents as well as upon gradual addition of NEt3, NaOH, and CH3SO3H. The DFT calculations were performed to verify the structures of 1-4 as well as their electronic and optical properties. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

In this work we report solvatochromic and luminescent properties of ethyl -salicylideneglycinate (), ethyl -(5-methoxysalicylidene)glycinate (), ethyl -(5-bromosalicylidene)glycinate (), and ethyl -(5-nitrosalicylidene)glycinate () dyes. - correspond to a class of -salicylidene aniline derivatives, whose photophysical properties are dictated by the intramolecular proton transfer between the OH-function and the imine N-atom, affording tautomerization between the enol-imine and keto-enamine forms. Photophysical properties of - were studied in different pure non-polar and (a)protic polar solvents as well as upon gradual addition of NEt, NaOH, and CHSOH. The DFT calculations were performed to verify the structures of - as well as their electronic and optical properties.

The Schiff base ligand H2L has been synthesized by condensation of 2-aminophenol with 3-methyl-1-phenyl-4-formylpyrazol-5-one and reaction between H2L and Ni(OOCR3)2, R = H in 1, –CH3 in 2, Cl in 3, yielded three new tetranuclear Ni(II) complexes. The complexes have been characterized by elemental analysis, IR- and ES-MS spectroscopy. Their structures as well as structure of ligand were determined by single-crystal X-ray diffraction. Compounds 1–3 possesses tetranuclear cubane-like structures containing [Ni4L4(R3COO)2]2 complex anions, which are charge balanced by two triethyl ammonium cations. Furthermore, the crystal structure of the Ni(II) cubane compound containing trichloroacetate bridging ligands, is reported for the first time. Variable temperature magnetic susceptibility measurements revealed interplay between ferromagnetic and antiferromagnetic exchange in the tetranuclear cubane-like compounds 1–3, in which ferromagnetic interactions were enhanced by introducing carboxylate bridging groups. DFT calculations supported the analysis of magnetic data.

Polysaccharide-based materials have been widely used as the first-choice candidates for various applications, especially in the field of biomaterials. The primary reasons for this are the sustainable nature of these materials and their high bioavailability. Their ability to be easily chemically modified enables them to be utilized in various avenues, with oxidation of the backbone being one of the most common chemical modifications. Additionally, these materials degrade via different pathways (enzymatically and chemically) and are hence ideal candidates for biomedical applications. This review summarizes the recent progress made with different oxidized polysaccharides and their potential applications to the field of biomaterials., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/17578

A Schiff base ligand was synthesized by the condensation of antipyrine-4-carboxaldehyde with 2-amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene and its Co(II), Ni(II), Cu(II) and Zn(II) complexes were prepared by microwave assisted solvent free synthesis. The biological activity of the prepared ligand and the metal complexes was assessed by in-vitro testing of their effect on the growth of various strains of bacteria and fungi. A gel electrophoresis assay demonstrated the ability of the complexes to cleave the pUC19 DNA. The alpha amylase inhibitory activity of the ligand and the metal complexes were evaluated and found that metal complexes possess higher activity than the ligand.

The Schiff base ligand H2L has been synthesized by condensation of 2-aminophenol with 3-methyl-1-phenyl-4-formylpyrazol-5-one and reaction between H2L and Ni(OOCR3)2, R = H in 1, –CH3 in 2, Cl in 3, yielded three new tetranuclear Ni(II) complexes. The complexes have been characterized by elemental analysis, IR- and ES-MS spectroscopy. Their structures as well as structure of ligand were determined by single-crystal X-ray diffraction. Compounds 1–3 possesses tetranuclear cubane-like structures containing [Ni4L4(R3COO)2]2 complex anions, which are charge balanced by two triethyl ammonium cations. Furthermore, the crystal structure of the Ni(II) cubane compound containing trichloroacetate bridging ligands, is reported for the first time. Variable temperature magnetic susceptibility measurements revealed interplay between ferromagnetic and antiferromagnetic exchange in the tetranuclear cubane-like compounds 1–3, in which ferromagnetic interactions were enhanced by introducing carboxylate bridging groups. DFT calculations supported the analysis of magnetic data.

A novel Schiff base ligand was synthesized by condensation of antipyrine-4-carboxaldehyde with 2-amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene and its Co(II), Ni(II), Cu(II) and Zn(II) complexes were prepared by microwave assisted solvent free synthesis. The characterization of the ligand and the metal complexes was performed through elemental analyses, molar conductance studies, 1H NMR, 13C NMR, UV–VIS, IR, FAB mass and ESR spectral analyses wherever possible and applicable. The spectral data revealed that the ligand acted as neutral tridentate coordinating to the metal ion through oxygen of the ester carbonyl group, azomethine nitrogen and carbonyl oxygen of antipyrine moiety. The XRD spectral data indicated the crystalline nature of the ligand and the copper(II) complex and both were indexed to orthorhombic crystal lattice

Organic-inorganic hybrid materials overcome drawbacks associated with alginate hydrogels. In this work, covalently coupled silica-alginate hybrids were prepared by Schiff base formation and sol-gel reaction using alginate dialdehyde (ADA), (3- Aminopropyl) triethoxysilane (APTES), and APTES/tetraethylorthosilicate (TEOS) precursors. The influence of the polysaccharide/inorganic ratio, the nature of the inorganic precursor and the ionic crosslinking ability are studied. Prepared hybrids were characterized by FT-IR, 13C and 29Si -NMR spectroscopies, SEM, and rheology. For ADA/APTES hybrids, at higher ADA content, Schiff base formation is predominant, but at lower ADA content, the sol-gel reaction is prevalent. However, the progress of the sol-gel reactions for ADA/(APTES+TEOS), is favored with higher ADA compositions. Introducing a posterior ionic crosslinking treatment was possible, increasing the moduli in ADA/(APTES+TEOS) hybrids from 86207Pa for 1.5 ADA/Si to 362171Pa for 1.5 ADA/Si-Ca. In-situ ADA-Silica hybrid hydrogels containing both ionic and covalent crosslinking can be successfully synthesized with the proposed method.

A salen-type Schiff base Zn(II) complex included in human serum albumin (HSA) protein was examined by UV-Vis, circular dichroism (CD), and fluorescence (PL) spectra. The formation of the composite material was also estimated by a GOLD program of ligand–protein docking simulation. A composite cast film of HSA and Zn(II) complex was prepared, and the effects of the docking of the metal complex on the degradation of protein molecules by mid-infrared free electron laser (IR-FEL) were investigated. The optimum wavelengths of IR-FEL irradiation to be used were based on experimental FT-IR spectra and vibrational analysis. Using TD-DFT results with 6-31G(d,p) and B3LYP, the IR spectrum of Zn(II) complex could be reasonably assigned. The respective wavelengths were 1652 cm−1 (HSA amide I), 1537 cm−1 (HSA amide II), and 1622 cm−1 (Zn(II) complex C=N). Degradation of HSA based on FT-IR microscope (IRM) analysis and protein secondary structure analysis program (IR-SSE) revealed that the composite material was degraded more than pure HSA or Zn(II) complex; the inclusion of Zn(II) complex enhanced destabilization of folding of HSA., Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub

To identify novel adenosine receptor (AR) ligands based on the chalcone scaffold, herein the synthesis, characterization and in vitro and in silico evaluation of 33 chalcones (15–36 and 37–41) and structurally related compounds (42–47) are reported. These compounds were characterized by radioligand binding and GTP shift assays to determine the degree and type of binding affinity, respectively, against rat (r) A1 and A2A ARs. The chalcone derivatives 24, 29, 37 and 38 possessed selective A1 affinity below 10 µM, and thus, are the most active compounds of the present series; compound 38 was the most potent selective A1 AR antagonist (Ki (r) = 1.6 µM). The structure–affinity relationships (SAR) revealed that the NH2-group at position C3 of ring A of the chalcone scaffold played a key role in affinity, and also, the Br-atom at position C3′ on benzylidene ring B. Upon in vitro and in silico evaluation, the novel C3 amino-substituted chalcone derivative 38—that contains an α,ß-unsaturated carbonyl system and easily allows structural modification—may possibly be a synthon in future drug discovery

Schiff bases, and their Cu(II) complexes, are known for their biological activity. In this work, antibacterial activity against Gram-negative strains of Escherichia coli, Pseudomonas aeruginosa and Staphylococcus pyogenes, as well as Gram-positive Staphylococcus pyogenes and Pseudomonas aeruginosa was studied, together with antifungal activity against Candida, Aspergillus, and Mucor strains. Also, technically simple, and rapid tests like ABTS, HORAC, and ORAC were used to investigate the antioxidant activity in order to compare obtained results with different type of tests.

The reactivity of the well-known pentadentate N3O2 Schiff base H2L (2,6-bis(2-hydroxyphenyliminomethyl)pyridine) towards a lanthanoid metal, in this case DyIII, has been investigated for the first time. This reactivity markedly depends on the pH of the medium and, accordingly, two different complexes, [Dy(HL)(NO3)2]·H2O (1·H2O) and [Dy(L)(NO3)(EtOH)(H2O)]·2H2O (2·2H2O), could be isolated from dysprosium(III) nitrate and H2L. In addition, reaction of H2L with dysprosium(III) chloride in methanol yields [Dy(HL′)2][Dy(L)(Cl2)] (3), where H2L′ ((6-(2-hydroxyphenyliminomethyl)-2-methoxyhydroxymethyl)pyridine) is an N2O2 hemiacetal donor derived from the partial hydrolysis of the H2L ligand, and subsequent addition of the methanol solvent to the carbonyl group. This latter reaction has been firstly observed for a lanthanoid metal. Single crystal X-ray diffraction studies of 1·1.15Py·0.3CH3C6H5, 2·2H2O and 3 show that the Schiff base is acting as a nearly flat pentadentate donor in all the cases, this behaviour being independent of the deprotonation degree of the phenolic oxygen atoms, both mono- or bisdeprotonated. Complexes 1·1.15Py·0.3CH3C6H5 and 2·2H2O show DyN3O6 cores, with distorted geometries closer to spherical tricapped trigonal prism or spherical capped square antiprism for 1·1.15Py·0.3CH3C6H5 and 2·2H2O, respectively. In the case of 3, the [Dy(HL′)2]+ cation shows a dysprosium ion in an N4O4 triangular dodecahedron environment, while the [Dy(L)(Cl2)]− anion displays a DyN3O2Cl2 core with distorted pentagonal bipyramidal geometry. Moreover, attempts to dilute 1·H2O with yttrium yielded single crystals of (Et3NH)[Dy0.09Y0.91(L)(NO3)2] (4), where the Schiff base shows a similar pentadentate coordination mode. Dynamic magnetic studies of 1·H2O, 2·2H2O and 3 show that 2·2H2O and 3 present field-induced slow relaxation of the magnetisation, with Ueff barriers of 46.1(9) and 31.0(7) K for 2·2H2O and 3, respectively, while 1·H2O does not exhibit frequency-dependent pea

The search for mononuclear lanthanoid-based single-ion magnets (SIMs) has increased the interest in some coordination environments with low coordination numbers, in combination with an axial symmetry, as they could maximize the anisotropy of complexes of oblate lanthanoid ions, such as dysprosium(III). In this sense, the pentagonal–bipyramid geometry can have ground-state doublets with perfect axiality, and therefore such complexes can be good candidates for SIMs. In our particular case, we have used a well-known open planar pentadentate chelating Schiff base ligand as 2,6-bis(1-salicyloylhydrazonoethyl)pyridine) (H4daps) for the synthesis of air-stable pentagonal–bipyramidal LnIII complexes (these being Ln: Dy and Er, oblate and prolate, respectively), in order to compare their structures. Thus, the reaction of H4daps with (CH3)4NOH·5H2O and the corresponding LnCl3·hexahydrate has yielded heptacoordinate [(CH3)4N][LnIII(H2daps)Cl2] complexes, where the tetramethylammonium cation is acting as the counterion of pentagonal–bipyramidal LnIII complexes, which are bearing two chloride atoms in apical positions. As both complexes could be crystallized as single crystals, we can compare their crystal structures, as well as with some other related complexes in the literature, which contain different counterions, trying to see their influence on other properties of the compounds, such as their magnetic behavior

High electrical conductivity material Fe-Chitosan Schiff base produced via two stages mechanism, reaction of salicylaldehyde and chitosan in three necked flask following the formation of complex by soak Chitosan Schiff base in FeCl3 solution in various times. The formed Schiff base was confirmed by presence of imine at 1604.77 cm-1. Next, Fe absorption was analyzed by using ICP-MS gives highest results at 492,51 ppm at 5 hours immersion time. The electrical conductivity exhibit tendency to increase and the highest point at 3.5 x 10-6 S cm­-1

An infrared free electron laser (IR-FEL) can decompose aggregated proteins by excitation of vibrational bands. In this study, we prepared hybrid materials of protein (human serum albumin; HSA) including several new Schiff base Zn(II) complexes incorporating amino acid (alanine and valine) or dipeptide (gly-gly) derivative moieties, which were synthesized and characterized with UV-vis, circular dichroism (CD), and IR spectra. Density functional theory (DFT) and time dependent DFT (TD-DFT) calculations were also performed to investigate vibrational modes of the Zn(II) complexes. An IR-FEL was used to irradiate HSA as well as hybrid materials of HSA-Zn(II) complexes at wavelengths corresponding to imine C=N, amide I, and amide II bands. Analysis of secondary structures suggested that including a Zn(II) complex into HSA led to the structural change of HSA, resulting in a more fragile structure than the original HSA. The result was one of the characteristic features of vibrational excitation of IR-FEL in contrast to electronic excitation by UV or visible light., Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub

The use of electrostatic interactions is fundamental in the the structure and function of biological enzymes, and has the potential to be a powerful tool in synthetic complexes as well. Electric fields generated by charged species have remarkable influence over electronic structure and intermolecular reactivity, and are capable of remarkable thermodynamic control in catalysis. Herein, a heterobimetallic platform consisting of a Schiff base binding site and an enchained crown ether ring is used to show a diverse range of effects that arise when a transition metal and a cation are placed in close proximity.In Chapter 1, spectroscopic and electrochemical techniques are used to demonstrate the role of electrostatic interactions on a nearby cobalt center. These experiments demonstrate the use of a wide range of cationic metals to impart significant shifts on the reduction potentials of a proximal transition metal center. Additionally, the role of solvent and anion coordination in the screening of electrostatic interactions are established.In Chapter 2, further studies are conducted with a nickel analogue of this heterobimetallic framework. Theoretical calculations are used to demonstrate the effect of electrostatics on the expanded molecular orbital manifold of metal Schiff base systems.In Chapter 3, a manganese complex is used to demonstrate the role of electrostatic interactions on reactivity. Extensive studies are carried out on the kinetic and thermodynamic considerations for the N-N coupling of Mn(V) nitrides, which showed that cationic charge is capable of stabilizing activated nitride species against bimolecular reactivity. The effect of proximal cations on ammonia oxidation and pKa are also explored.

Abstract: The efficient preparation of functional rigid and soluble macrocycles remains a challenge for synthetic chemists. Here, we exploit the thermodynamic control of dynamic covalent chemistry to investigate the influence of the monomer structure on the macrocyclization selectivity. A series of rigid cyclic hexamer has been synthesized by imine condensation of benzene building blocks, i.e. meta-substituted diamines and dialdehydes, templated by calcium(II) chloride. The monomers were designed to feature various additional functional groups either available for further post-cyclization modifications or acting as solubilizing groups. The cyclization selectivity was systematically investigated and optimized depending on the length of the applied solubilizing group and on the nature of the additional functional group. A selectivity up to 92% was reached for the macrocyclization exhibiting trifluoromethyl and bromine groups at the outer periphery and hydroxyl groups in the cavity. Graphic abstract: [Figure not available: see fulltext.].

We have explored the suitability of an O,N,N–donor Schiff base (H2SB) for obtaining dinuclear complexes with heavy metal ions such as Cu2+, Zn2+, Ni2+, and Co2+ (borderline acids) as well as Pd2+ and Cd2+ (soft acids). Spectroscopic studies demonstrated that the complexation of H2SB and Cu2+, Zn2+, Ni2+, Co2+, Pd2+, and Cd2+ occurred at a 1:1 stoichiometry. We have found two square planar centers with Pd-N-Pd angles of 93.08(11)° and a Pd–Pd distance of 3.0102(4) Å in Pd2(SB)2·Me2CO. This Pd–Pd distance is 30% shorter than the sum of the van der Waals radii, which is in accordance with a strong palladophilic interaction. Fluorescence studies on H2SB-M2+ interaction showed that H2SB can detect Cu2+ ions in a sample matrix containing various metal ions (hard, soft, or borderline acids) without interference. Determination of binding constants showed that H2SB has a greater affinity for borderline acids than for soft acids

© 2019 Elsevier B.V. According to World Health Organization (WHO) infectious diseases are spreading faster and emerging more quickly than ever before. Due to the increasing incidents related with new and reemerging infectious diseases, discovery and development of new antimicrobial compounds with diverse structures and action mechanism is urgently needed. The antibacterial effects of lanthanides (Ln) have been studied since the 19th century and have been employed since then with more or less success in treatment of various diseases. This review gathers together all the studies dealing with the antimicrobial activity of Ln(III) complexes published until now. Overall, it was discovered that the antimicrobial activity of the Ln complexes is greater than the activity of the free ligand (L), indicating that the complexation with the Ln enhances the activity of the L. In some cases Ln complexes exhibit antimicrobial activity similar or even better than the activity of standard antimicrobial agents. These results are encouraging, Ln complexes representing a possible alternative to antimicrobial agents used currently.

Šifove baze i njihovi kompleksi pokazuju različitu biološku aktivnost poput antiviralne, antimikrobne, antimalarijske i antikancerske. Zbog činjenice da biološka aktivnost jedinjenja zavisi prvenstveno od lipofilnosti molekula, što je posledica strukture jedinjenja, određivanje i korelacija lipofilnosti sa hemijskom strukturom, kao i određivanje biološke aktivnosti su postali nezaobilazni u sintezi novih lekova..., Schiff bases and their complexes are versatile compounds which have various biological activities such as antiviral, antimicrobial, antimalarial, and anticancer activity. Biological activity of compounds depends on their molecular structure, especially lipophilic character. Determination of lipophilicity, its correlation with chemical structure, and biological activity is very important in drug design...

The present article reports on the syntheses, crystal structures and luminescence properties of three solvate forms of a zinc(II) complex containing 4-{(E)-[(2-fluorophenyl)imino]methyl)-5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one (HL). The reaction of zinc(II)acetate with the HL ligand in ethanol and acetonitrile led to the formation of two solvate analogues [Zn(L)(2)]center dot Solv (Solv - ethanol (1) and acetonitrile (2)). The properties of the [Zn(L)(2)]center dot Solv complexes were investigated by UV-Vis absorption and fluorescence emission spectroscopy, and the density functional theory calculations. Bader's topological analysis was performed to investigate the electronic peculiarities of Zn(II) polyhedra and non-covalent interactions within crystal packing of studied solvates. (C) 2018 Elsevier Ltd. All rights reserved.

The amine transaminase from Chromobacterium violaceum (Cv-ATA) is a pyridoxal-5’-phosphate (PLP)dependent enzyme. The biological activity of this enzyme requires the formation of a holo homo dimer.The operational stability of Cv-ATA is, however, low due to dimer dissociation. At the enzyme dimeric interface, two phosphate group binding cups (PGBC) are located. Each cup coordinates the phosphate group of PLP by hydrogen bonds originating from both subunits. Hypothetically, molecular coordination of phosphate groups (PLP or free inorganic phosphate) into the PGBC can affect both dimer stabilization and enzyme activity. To test this assumption, the influence of phosphate (as a functional group in PLP or as free inorganic anions) on the stability and activity of Cv-ATA was explored by various biophysical techniques. The results show that Cv-ATA has a relatively low affinity towards PLP, which results in an excess of apo dimeric enzyme after enzyme purification. Incubation of the apo dimer in buffer solution supplemented with PLP restored the active holo dimer. The addition of PLP or inorganic phosphate into the enzyme storage solutions protected Cv-ATA from both chemical and long term storage unfolding. The use of phosphate buffer leads to faster inactivation of the holo enzyme, compared to the use of HEPES buffer. These results open up for new perspectives on how to improve the stability of PLP-dependent enzymes., QC 20180320

Fluorescent chemodosimeters based on organic molecules have been widely used in sensing applications. However, the study of ratiometric fluorescent organic chemodosimeters is not thoroughly. The major problem is their poor solubility in aqueous solutions, resulting in notorious aggregation caused quenching (ACQ) effect. In this work, two different strategies were used to overcome the ACQ effect and a series of ratiometric fluorescent pH chemodosimeters (1–3) were developed. In alkaline condition, 1–3 underwent deprotonation processes, producing 1a–3a with negative charges to avoid the formation of aggregations. While in acidic condition, 1–3 underwent bimolecular condensation reactions, resulting in the formation of salicylaldehyde azine (SAA) derivatives (1b–3b). SAA derivatives, a kind of classic aggregation-induced emission (AIE) luminogens which exhibit intense emission in their aggregated states, can effectively overcome the ACQ effect. This work provides a new approach for designing aqueous solution available ratiometric fluorescence chemodosimeters based on organic molecules. © 2018 Elsevier B.V.

The Schiff base (HLBr), containing a chelating unit and triphenylphosphonium moiety has been synthesized in the reaction of 4-aminobenzyl(triphenyl)phosphonium bromide with 5-hydroxy-3-methyl-1-phenyl-4-formylpyrazole. The composition and structure of HLBr have been determined by elemental analysis, IR, 1D and 2D NMR, electronic spectroscopy and mass spectrometry. Density functional theory (DFT) calculations (6-311G(d,p) level of theory) have been carried out to investigate tautomeric forms of HL+ and the reaction mechanism of its formation and spectral properties. The most stable form in the solid state and in DMSO solution is pyrazolone (keto-amine) tautomeric form. [GRAPHICS] .

Cobalt(III) complexes derived from thio-and selenosemicarbazone ligands have been studied to elucidate the nature and consequences of S to Se substitution on their possible biological activity. Solid state structures of cobalt(III) complexes with bis-tridentate coordinated 2-quinolinecarboxaldehyde thio-and selenosemicarbazone were determined by single crystal X-ray diffraction analysis. The complexes were also characterized by spectroscopic methods and cyclic voltammetry. Electronic properties of the complexes were studied using DFT and TD-DFT methods. Finally, evident in vitro antioxidant activity of the complexes was demonstrated.

Cobalt(III) complexes derived from thio-and selenosemicarbazone ligands have been studied to elucidate the nature and consequences of S to Se substitution on their possible biological activity. Solid state structures of cobalt(III) complexes with bis-tridentate coordinated 2-quinolinecarboxaldehyde thio-and selenosemicarbazone were determined by single crystal X-ray diffraction analysis. The complexes were also characterized by spectroscopic methods and cyclic voltammetry. Electronic properties of the complexes were studied using DFT and TD-DFT methods. Finally, evident in vitro antioxidant activity of the complexes was demonstrated.

Cobalt(III) complexes derived from thio-and selenosemicarbazone ligands have been studied to elucidate the nature and consequences of S to Se substitution on their possible biological activity. Solid state structures of cobalt(III) complexes with bis-tridentate coordinated 2-quinolinecarboxaldehyde thio-and selenosemicarbazone were determined by single crystal X-ray diffraction analysis. The complexes were also characterized by spectroscopic methods and cyclic voltammetry. Electronic properties of the complexes were studied using DFT and TD-DFT methods. Finally, evident in vitro antioxidant activity of the complexes was demonstrated.