Search

The BiFeO3 –NaNbO3 electroceramics, synthesized by the ceramic method, are studied aiming to obtain materials with a well-defined thermistor response coexisting with a relevant magnetic response. XRD data and Raman analysis reveal a structural transition as a function of composition. Compositional features explored from ICP, XPS and EDS measurements, suggest compositional heterogeneity leading to a cluster-type scenario implying NNO-rich and BFO-rich regions in the samples. Impedance spectroscopy data reveal the development of a PTCR thermistor response for x ≥ 0.5 near room temperature. The x = 0.9 ceramic shows resistivity changes of about six orders of magnitude in the first thermal cycle and maximum permittivity values of ∼ 105, much higher than those previously reported for BFO-doped ceramics. Magnetization data are interpreted in terms of the stabilization of superparamagnetic clusters. The response displayed by the x = 0.9 ceramic makes it a promising multifunctional material for device applications.

Highly sodium deficient Na0.6NbO3 (NN) ceramics were prepared and characterized. Their mean structure could be described by a mixture of the predominant P polymorph (S.G. Pbma) and the Q phase (S.G. P21ma), at room temperature, as deduced from Rietveld refinements of Powder X-ray diffraction and Raman scattering data. Besides, microstructural and compositional heterogeneity was evidenced from HRTEM and XPS analyses. Dielectric measurements on this highly vacancies-containing NN material indicated a hysteretic transition taking place at ~12 and −18 °C on the heating and cooling regimes, respectively. This means a considerable shift to lower temperatures of the transition temperatures concerning the P/Q transformations previously described for the NaNbO3 material. At an intermediate frequency of 10 kHz, maximum permittivity and tangent loss values of e' = 1250 and tgδ = 2 were obtained on heating, whereas lower values of e' = 65 and tgδ = 0.04 were displayed on cooling regime. These anomalies were interpreted in terms of ferrolectric-antiferroelectric-paralectric phase-transitions implying a PTCR behavior within certain temperature range. This response, observed in this complex material for the first time, has interesting implications for the possible application of NN ceramics in sensing and dielectric materials fields.

Herein, we report the vibrational and optical properties of new Cu2ZnSn1-xGexS2Se2 solid solutions prepared by isomorphic substitution of a fraction of Se by S in Cu2ZnSn1-xGexSe4 (CZTGeSe) through ceramic method. The Raman spectra and x-ray diffraction analysis on samples confirms that they crystallize in Kesterite-type structure. The Raman peaks were analyzed by fitting of the spectra allowing identification the vibrational modes by comparison with experimental and theoretical data from CZTGeSe and CZTGeS end-members. The dependency between the amount of cation and chalcogen substituent in optical characterization shows band gap around of 1.36 eV, close to the optimum value for solar cells with high efficiency.

Selenospinels, CuCr2−xMxSe4 (M = Zr and Sn), were synthesized via conventional solid-state reactions. The crystal structure of CuCr1.5Sn0.5Se4, CuCr1.7Sn0.3Se4, CuCr1.5Zr0.5Se4, and CuCr1.8Zr0.2Se4 were determined using single-crystal X-ray diffraction. All the phases crystallized in a cubic spinel-type structure. The chemical compositions of the single-crystals were examined using energy-dispersive X-ray analysis (EDS). Powder X-ray diffraction patterns of CuCr1.3Sn0.7Se4 and CuCr1.7Sn0.3Se4 were consistent with phases belonging to the F d 3 ¯ m Space group. An analysis of the vibrational properties on the single-crystals was performed using Raman scattering measurements. The magnetic properties showed a spin glass behavior with increasing Sn content and ferromagnetic order for CuCr1.7Sn0.3Se4.

We report the synthesis, characterization and thermoelectric properties of lead-free AgSnmSbSe2Tem (m = 2 and 10) systems. Powder X-ray diffraction patterns and Rietveld refinement results were consistent with phases belonging to the P m 3 ¯ m space group. The microstructures and morphologies of these systems were investigated using scanning electron microcopy (SEM) and high-resolution transmission electron microscopy (HRTEM). Parallelepiped bars for transport measurements were prepared using two methods: the classical method (CM) from melted samples and the spark plasma sintering (SPS). The AgSnmSbSe2Tem (m = 2 and 10) systems exhibited typical degenerate semiconductor behavior, with a carrier concentration of approximately +1021 cm−3. We determined that the Seebeck coefficient can be substantially increased from approximately +40 μV K−1 (CM) to +70 μV K−1 (SPS) in AgSn2SbSe2Te2 at room temperature. Consequently, the power factor (S2σ) was ∼22 μW cm−1 K−2. On the basis of the electrical and thermal transport properties, ZT values of ∼0.10 were obtained at room temperature.

Quaternary alkyl 2-phenylpyridinium and 2-(2,4-difluorophenyl)pyridinium amines with iodide, hexafluorophosphate and bis(trifluoromethylsulfonyl)imide anions have been fully characterized by 1H NMR, FT-IR and MALDI mass spectroscopic methods and studied by quantum chemistry calculations. The compounds with bis(trifluoromethylsulfonyl)imide anion can be classified as ionic liquids, because they melt at room temperature. The quaternary amines with iodide and hexafluorophosphate anions are solid at 25 °C. The X-ray diffraction characterization of the 2-(2,4-difluorophenyl)-1-methylphenylpyridinium hexafluorophosphate and 1-ethyl-2-(2,4-difluorophenyl)phenylpyridinium hexafluorophosphate show an extensive series of C H⋯F, C F⋯π and P F⋯π intermolecular interactions, which give rise to a supramolecular network. The relationship between the solid-state structures and the melting points is discussed by the evaluation of the thermal behavior based on experimental data from Differential Scanning Calorimetry (DSC) studies, and also using the analysis of the ion pairs binding energies. These new compounds based on phenylpyridine allow us to grow the diversity of ionic liquids and their crystalline salts, increasing the knowledge about the chemical and physical properties of these ionic species.

Two new organometallic compounds with the general formula [Ru(η6-anethole)(en)(X)]PF6, where X = Br (5) or I (6) and en = ethylenediamine, were synthesized and fully characterized using standard techniques (NMR, MS and elemental analysis). Displacement of the proton and carbon aromatic chemical shifts of anethole to the upper field in both compounds indicated organometallic Ru(η6-anethole) bond formation, and the characteristic “piano-stool” structure of these types of compounds was confirmed by the single crystal X-ray diffraction of compound 5. Compounds 5 and 6 exhibited interesting cytotoxicity, especially toward the human colon tumor cell line HT-29, similar to the previously studied compound [Ru(η6-anethole)(en)(Cl)]PF6 (4). A slight tendency toward cytotoxicity could be observed by varying the halogen leaving group (IC50 value): 6 (10 ± 2 μM) > 5 (18 ± 2 μM) = 4 (18 ± 3 μM). Compound 6 showed 3-fold more biological activity in HT-29 cells than toward the non-tumor colon cell line CCD-841, making it an interesting candidate for further studies and drug development.

A highly regioselective solvent-free microwave-assisted synthesis of pyrazoles and tetrahydroindazoles based on the condensation of 1,3-diketones with arylhydrazines is described. Compounds were evaluated as cholinesterase inhibitors in order to identify an alternative treatment for Alzheimer's disease. All compounds displayed moderated acetylcholinesterase inhibitory activity and most of the compounds displayed remarkable butyrylcholinesterase inhibitory activity and selectivity. The compounds 3y and 3i with IC50 of 1.65 and 3.59 µM, respectively, were the most active and selective compounds as butyrylcholinesterase inhibitors. Likewise, the compounds were tested as antioxidants agents, results showed that they have the ability to trap free-radicals. Molecular Docking studies showed a key π-π stacking interaction of most of the compounds with residue Trp82 within of butyrylcholinesterase active site. Molecular quantum similarity field, global and local reactivity descriptors, and the Fukui functions were calculated in the Density Functional Theory framework to analyze the reactivity patterns along with the molecular set.

Two hitherto unknown organometallic compounds with antitumor activity, [Ru(η6-2-(1-propenyl)anisole)(en)(Cl)]PF6 (3) and [Ru(η6-2-(1-propenyl)anisole)(en)(l)]PF6 (4), where en is ethylenediamine, were synthesized and completely characterized using standard techniques (1H and 13C NMR, high-resolution MS and elemental analysis). The lipophilicity and hydrolysis rate kinetics were assessed and compared to the previously reported [Ru(η6-4-(1-propenyl)anisole)(en)(halogen)]PF6 derivatives (4-(1-propenyl)anisole or anethole), where the halogen is Cl (1) or I (2). Based on the obtained rate constants, the coordination of (1-propenyl)anisole to the Ru(en) moiety yielded organometallic compounds that are as active as compounds that bind p-cymene as the arene ligand. Consistent with previously reported kinetic data, our density functional theory-based computational study revealed that an associative interchange mechanism predominates in the hydrolysis of this type of compound, and only small variations (∼1 kcal mol−1) were observed between the stabilities of the transition states corresponding to different derivatives. In vitro analyses of the anti-proliferative activity revealed that compounds 1 to 3 generally exhibit better cytotoxicity and selectivity (tumor versus non tumor cells) toward the gastric tumor cell lines AGS and SNU-1, compared to the parent [Ru(η6-p-cymene)(en)X]PF6 (X: Cl and I) systems. Compound 3 showed similar cytotoxicity to compound 1 toward the AGS cell line, indicating that the change in the substitution pattern of the coordinated arene from 4-(1-propenyl)anisole to 2-(1-propenyl)anisole did not prominently affect the biological behavior. Compound 2 remained the most promising candidate to treat gastric cancer.

An efficient, green, and atom economic methodology for the stereoselective synthesis of C2 symmetry (3R,4R)-TTFOL diester derivatives has been developed. The procedure occurs through a (2R,3R)-TADDOL dioxolane cleavage and rearrangement under mild conditions by its reaction with a carboxylic acid in the presence of TFAA/H3PO4 without the need for an inert atmosphere to give generally high yields.

This work reports the synthesis by solid–state reaction of Cu 2 Fe 1- x Co x SnS 4 solid solutions. Crystal structures of Cu 2 Fe 0.8 Co 0.2 SnS 4 and Cu 2 Fe 0.6 Co 0.4 SnS 4 were investigated by single crystal X-ray diffraction. Both phases crystallize in the tetragonal stannite-type structure. The volume of the tetrahedral [MS 4 ] (M = Fe, Co) presented the highest distortion, with Edge-Length Distortion (ELD) indices ∼2% from the ideal tetrahedron. The powder X-ray diffraction (XRD) patterns of Cu 2 Fe 1- x Co x SnS 4 ( x = 0.2, 0.4, 0.6 and 0.8) has been refined by Rietveld method. No secondary phases were detected in XRD patterns. An analysis of the vibrational properties of Cu 2 Fe 1- x Co x SnS 4 was performed using Raman scattering measurements. The Raman peaks were analyzed by fitting of the spectra and subsequently identifying the vibrational modes by comparison with experimental and theoretical data from Cu 2 FeSnS 4 (CFTS) and Cu 2 CoSnS 4 (CCTS) end-members. The spectra from Cu 2 Fe 1- x Co x SnS 4 show that there is a variation in the frequency of the main A 1 peak at ∼320 cm −1 together with a decrease in the secondary mode intensity at ∼285 cm −1 . Full Width at Half Maximum (FWHM) and the intensity of the Raman peaks reflect the high crystallinity of Cu 2 Fe 1- x Co x SnS 4 solid solutions. The oxidation states of the metals were confirmed by temperature-dependent magnetization measurements performed in the antiferromagnetic Cu 2 Fe 1- x Co x SnS 4 solid solutions.

Five new organometallic Ru(II) compounds (VI−X) with the general formula [Ru(η6-arene)(N,N)Cl]PF6, where arene-N,N correspond to methylisoeugenol-bipyridine (VI); anethole-bipyridine (VII); methylisoeugenol-ethylenediamine (VIII); anethole-ethylenediamine (IX) and methylisoeugenol-1,2-diaminobenzene (X), have been synthesized, fully characterized and biologically evaluated in vitro. The reaction conditions based on the reduction of [Ru(1,5-COD)Cl2]n in situ with methyleugenol and estragole, which are natural ligands, induced an alkene isomerization on the allylic substituent of coordinated arenes. The Ru(II)-arene bond formation and isomerization of the C C bond on the allyl substituent was confirmed using 1H NMR spectroscopy; this result was validated for compound VIII by X-ray diffraction. An XRD analysis revealed the presence of both enantiomers of the complex in the single-crystal. Compounds IX and X exhibited a better cytotoxic activity in vitro than carboplatin, which is a commercial drug, against three human tumor cell lines (MCF-7, PC-3 and HT-29).

The nominal compositions Ag0.8Cu0.2SbS2 and Ag0.7Cu0.3SbS2 have been synthesized by conventional ceramic solid-state reaction at high temperature. X-ray diffraction (XRD) and scanning electron microscopy chemical analysis (SEM-EDAX) revealed single phases, isostructural to the natural miargyrite α-AgSbS2 mineral. Examination of the lattice parameters shows a decrease in the cell volume with increasing copper substitutions. The Raman analysis displays absorptions which may be assigned to the Sb–S stretching vibrations of the SbS3 pyramids. The impedance-frequency analysis showed grain boundary and electrode interface contributions in non-Debye type relaxation, following Jonscher's universal power law. The giant permittivity response is attributed to extrinsic effects without evidence of a ferroelectric transition. Summerfield scaling, leading to the superposition of impedance analysis, implies that the relaxation is thermally activated, without introducing more than one underlying transport mechanism.

The chalcone and bis-chalcone derivatives have been synthesized under sonication conditions via Claisen-Schmidt condensation with KOH in ethanol at room temperature (20–89%). The structures were established on the basis of NMR, IR, Single-crystal XRD, and MS. The best compound 3u had inhibitory activity (IC50 = 7.50 µM). The synthesis, the antioxidative properties, chemical reactivity descriptors supported in Density Functional Theory (DFT), acetylcholinesterase (AChE) inhibition and their potential binding modes, and affinity were predicted by molecular docking of a number of morpholine-chalcones and quinoline-chalcone. A series of bis-chalcones are also reported. Molecular docking and an enzyme kinetic study on compound 3u suggested that it simultaneously binds to the catalytic active site (CAS) and peripheral anionic site (PAS) of AChE. Moreover, the pharmacokinetic profile of these compounds was investigated using a computational method.

2-bromo-N-(2,4-difluorobenzyl)benzamide was synthesized in 92% yield by the reaction of commercial 2-bromobenzoic acid with (2,4-difluorophenyl)methanamine. The new title compound was characterized by 1H and 13C NMR, EI-MS and FT-IR. The crystal structure was stablished by single-crystal X-ray diffraction analysis. The colorless plates crystallized in monoclinic system, space group P21/n, with a = 15.1112(11) A, b = 4.8926(3) A, c = 17.4796(13) A, β = 91.167(7)°, V = 1292.05(16) A3 and Z = 4. The refinement converged to R1(F)= 0.0380, wR2(F2) = 0.1226 and S = 1.008. The supramolecular packing array involves N H⋅⋅⋅O hydrogen-bonds and C-Br⋅⋅⋅π intermolecular interactions. Theoretical calculation of the title compound was carried out with HF/6–31 G, HF/6–31G(d, p), DFT-B3LYP/6–31 G, DFT-B3LYP/6–31G(d, p), DFT-M02X/6–31 G and DFT-M02X/6–31G(d, p).

The (Mn 1− x Cd x )Cr 2 S 4 phases (0 ≤ x ≤ 0.6) have been synthesized from the corresponding elements at 1123 K. These samples were characterized by powder X-ray diffraction (XRD) and magnetic susceptibility. The (Mn 1− x Cd x )Cr 2 S 4 compounds crystallize in the space group Fd-3m with cell parameters a = 10.101(6) A, 10.139(3) A, 10.165(2) A, and 10.192(1) A for x = 0, 0.2, 0.4 and 0.6, respectively. An overall ferrimagnetic behavior is observed for all samples. The ferromagnetic component increases rapidly when manganese is substituted by non-magnetic cadmium, as shown by ZFC/FC measurements. At the same time, the value of the magnetization M 50 at 50 kOe, deduced from M ( H ) loops, also increases with increasing cadmium content because the antiferromagnetic alignment between chromium and manganese spins is progressively lost, leading toward well aligned moments pointing into the same direction. These results are explained by a rearrangement of the chromium spins when Mn located at the tetrahedral sites, is substituted by Cd.

A new quaternary alkali metal, rare earth thiophosphate was synthesized by the ceramic method and characterized by single crystal X-ray diffraction: K 2 SmP 2 S 7 crystallizes in the monoclinic space group C 2 (no. 5) with the unit cell parameters a = 22.746(5) A, b = 6.7362(13) A, c = 8.9004(18) A, β = 99.68(3)°, V = 1344.3(5) A 3 and Z = 2. The phase K 2 SmP 2 S 7 can be better described as K 4 Sm 2 [PS 4 ] 2 [P 2 S 6 ] because it contains in the crystal structure both discrete anions [PS 4 ] 3− and [P 2 S 6 ] 4− . The crystal structure consists of infinite chains of 1 ∞ [SmPS 4 ] that are linked together through the ethane-like [P 2 S 6 ] 4− anions to form two-dimensional layers. The packing of K 2 SmP 2 S 7 is formed by layers of 2 ∞ [Sm 2 [PS 4 ] 2 [P 2 S 6 ]] 4− separated by K + cations. K 2 SmP 2 S 7 was characterized by Raman and Fourier transform infrared (FTIR) spectroscopy and SEM-EDX microprobe analyses. The optical band gap of K 2 SmP 2 S 7 was determined by UV–vis diffuse reflectance measurements to be 2.59 eV.

The new phases α-NaSbP 2 S 6 and β-NaSbP 2 S 6 were synthesized by ceramic and reactive flux methods at 773 K. The structures of α-NaSbP 2 S 6 and β-NaSbP 2 S 6 were determined by the single-crystal X-ray diffraction technique. α-NaSbP 2 S 6 crystallizes in the monoclinic space group P 2 1 / c with a = 11.231(2) A, b = 7.2807(15) A, c = 11.640(2) A, β = 108.99(3)°, V = 900.0(3) A 3 and z = 4. β-NaSbP 2 S 6 crystallizes in the monoclinic space group P 2 1 with a = 6.6167(13) A, b = 7.3993(15) A, c = 9.895(2) A, β = 92.12(3) °, V = 484.10(17) A 3 and z = 2. The α- and β-phases of NaSbP 2 S 6 are closely related, the main difference lies in the stacking of the [Sb[P 2 S 6 ]] n n − layers. The structure of α-NaSbP 2 S 6 consists of two condensed layers (MPS 3 type) to give an ABAB… sequence with Na + cations located in the interlayer space. The packing of β-NaSbP 2 S 6 is formed by monolayers of [Sb[P 2 S 6 ]] n n − stacked in an AA… fashion separated by a layer of Na + cations. Both phases are derivates of the M 1+ M 3+ P 2 Q 6 family. The optical band gaps of α-NaSbP 2 S 6 and β-NaSbP 2 S 6 were determined by UV–vis diffuse reflectance measurements to be 2.17 and 2.25 eV, respectively.

The new quaternary selenophosphate phases AMP 2 Se 6 (A=Cu, Ag and M=Bi, Sb) were synthesized by ceramic methods at 1023 K. These phases were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray analysis (EDX) and a.c. and d.c. electrical conductivity measurements. The phases all show values of electrical conductivity, σ , of about 10 −4 Ω −1 cm −1 at 303 K and photoconductive effect. The conductivity is nearly five orders of magnitude larger than that of related phases.

The intercalation compounds (Polyaniline)1.08Mn0.86PS3 and (Polyaniline)0.57Cd0.73PS3 have been synthesized by the ion-exchange procedure. These compounds constitute a new family of intercalates in MPS3 (M = Mn, Cd) host layer, with Polyaniline as guest species. They have been characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FTIR), differential thermal analysis (DTA), thermogravimetric analysis (TGA), and electrical conductivity measurements. Both intercalation compounds show values of electrical conductivity (σi) of about 10−7 Ω−1 cm−1 at 298 K and photoconductivity at temperatures from 296 to 343 K.