Peculiarities of the crystal structure evolution of Bifeo3-batio3 ceramics across structural phase transitions

Evolution of the crystal structure of ceramics BiFeO3-BaTiO3 across the morphotropic phase boundary was analyzed using the results of macroscopic measuring techniques such as X-ray diffraction, differential scanning calorimetry, and differential thermal analysis, as well as the data obtained by local scale methods of scanning probe microscopy. The obtained results allowed to specify the concentration and temperature regions of the single phase and phase coexistent regions as well as to clarify a modification of the structural parameters across the rhombohedral-cubic phase boundary. The structural data show unexpected strengthening of structural distortion specific for the rhombohedral phase, which occurs upon dopant concentration and temperature-driven phase transitions to the cubic phase. The obtained results point to the non-monotonous character of the phase evolution, which is specific for metastable phases. The compounds with metastable structural state are characterized by enhanced sensitivity to external stimuli, which significantly expands the perspectives of their particular use. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Instituto Nacional de Ciência e Tecnologia para Excitotoxicidade e Neuroproteção, INCT-EN: UID/04564/2020, UIDB/50011/2020, UIDP/50011/2020Russian Science Foundation, RSF: 18-19-00307Funding: This work was supported by the RSF (project #18-19-00307). Investigations performed at the Center for Physics of the University of Coimbra were supported by Fundação para a Ciência e a Tecnologia (project UID/04564/2020). M.V.S. acknowledges Russian academic excellence project “5-100” for Sechenov University. Part of work done at the University of Aveiro was developed within the scope of the project CICECO-Aveiro Institute of Materials, refs. UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the FCT/MEC

Characteristic of physicochemical properties of Pd/MgO catalysts used in the hydrodechlorination process with CCl4

The aim of this paper was to investigate the physicochemical properties of palladium catalyst containing basic support MgO which was used in hydrodechlorination reaction with carbon tetrachloride. In order to characterize the investigated sample the catalyst was put to tests of XRD, TOF - SIMS, TG-DTA-MS and TPR(H2), measurements, activity tests were also performed. The XRD and TPR results demonstrated the presence of PdOxCly species whose decomposition takes place above 700°C. The calcination of the Pd/MgO catalyst at 700°C resulted in the transformation of PdOxCly to PdO

Molecular and crystalline architectures based on HgI2: From metallamacrocycles to coordination polymers

Three metallamacrocycles and one coordination polymer were obtained by using coordination driven self-assembly of the HgI2 salt with four different ligands: 2,2′-butan-1,4-diylbis(oxy)dianiline (L1), 1,4-bis(2′-formylphenyl)-1,4-dioxabutane bis(isonicotinoylhydrazone) (L2), (E)-N′-(pyridin-3-ylmethylene)isonicotinohydrazide (L3) and (E)-1-(pyridin-3-yl)-N-(pyridin-3-ylmethyl)methanimine (L4). The coordination compounds were studied by elemental analysis, FT-IR spectroscopy and single-crystal X-ray diffraction analyses. Reaction of the HgI2 salt with L1, L2 and L3 yields metallamacrocycles of formula [(HgI2)2(μ-L1)2] (1), [(HgI2)2(μ-L2)2] (2), [HgI2(μ-L3)]4 (3). In contrast, the reaction with L4 under the same conditions yields a coordination polymer of formula [{HgI2(L4)}]n (4). In addition, the X-ray structure of L2 is also reported. The influence of the flexibility of the ligand on the final shape and nuclearity of the macrocycle is also analysed. Hirshfeld surface analysis and fingerprint plots facilitate a comparison of intermolecular interactions in all compounds, which are crucial in the construction of the supramolecular architectures. Finally, some noncovalent interactions have been evaluated energetically using DFT calculations and characterized using Bader's theory of atoms-in-molecules. © The Royal Society of Chemistry 2017

Ionic elastomers based on carboxylated nitrile rubber (XNBR) and magnesium aluminum layered double hydroxide

International audienceThe presence of carboxyl groups in carboxylated nitrile butadiene rubber (XNBR) allows it to be cured with different agents. This study considers the effect of crosslinking of XNBR by magnesium aluminum layered double hydroxide (MgAl-LDH), known also as hydrotalcite (HT), on rheometric, mechano-dynamical and barrier properties. Results of XNBR/HT composites containing various HT loadings without conventional curatives are compared with XNBR compound crosslinked with commonly used zinc oxide. Hydrotalcite acts as an effective crosslinking agent for XNBR, as is particularly evident from rheometric and Fourier transform infrared spectroscopy (FTIR) studies. The existence of ionic crosslinks was also detected by dynamic mechanical analysis (DMA) of the resulting composites. DMA studies revealed that the XNBR/HT composites exhibited two transitions - one occurring at low temperature is associated to the T-g of elastomer and the second at high temperature corresponds to the ionic transition temperature T-i. Simultaneous application of HT as a curing agent and a filler may deliver not only environmentally friendly, zinc oxide-free rubber product but also ionic elastomer composite with excellent mechanical, barrier and transparent properties

Coupling 6-chloro-3-methyluracil with copper: structural features, theoretical analysis, and biofunctional properties

As nucleobases in RNA and DNA, uracil and 5-methyluracil represent a recognized class of bioactive molecules and versatile ligands for coordination compounds with various biofunctional properties. In this study, 6-chloro-3-methyluracil (Hcmu) was used as an unexplored building block for the self-assembly generation of a new bioactive copper(ii) complex, [Cu(cmu)2(H2O)2]·4H2O (1). This compound was isolated as a stable crystalline solid and fully characterized in solution and solid state by a variety of spectroscopic methods (UV-vis, EPR, fluorescence spectroscopy), cyclic voltammetry, X-ray diffraction, and DFT calculations. The structural, topological, H-bonding, and Hirshfeld surface features of1were also analyzed in detail. The compound1shows a distorted octahedral {CuN2O4} coordination environment with twotranscmu−ligands adopting a bidentate N,O-coordination mode. The monocopper(ii) molecular units participate in strong H-bonding interactions with water molecules of crystallization, leading to structural 0D → 3D extension into a 3D H-bonded network with atfz-dtopology. Molecular docking and ADME analysis as well as antibacterial and antioxidant activity studies were performed to assess the bioactivity of1. In particular, this compound exhibits a prominent antibacterial effect against Gram negative (E. coli, P. aeruginosa) and positive (S. aureus, B. cereus) bacteria. The obtained copper(ii) complex also represents the first structurally characterized coordination compound derived from 6-chloro-3-methyluracil, thus introducing this bioactive building block into a family of uracil metal complexes with notable biofunctional properties. © The Royal Society of Chemistry 2021

Molecular and crystalline architectures based on HgI2: From metallamacrocycles to coordination polymers

Three metallamacrocycles and one coordination polymer were obtained by using coordination driven self-assembly of the HgI2 salt with four different ligands: 2,2′-butan-1,4-diylbis(oxy)dianiline (L1), 1,4-bis(2′-formylphenyl)-1,4-dioxabutane bis(isonicotinoylhydrazone) (L2), (E)-N′-(pyridin-3-ylmethylene)isonicotinohydrazide (L3) and (E)-1-(pyridin-3-yl)-N-(pyridin-3-ylmethyl)methanimine (L4). The coordination compounds were studied by elemental analysis, FT-IR spectroscopy and single-crystal X-ray diffraction analyses. Reaction of the HgI2 salt with L1, L2 and L3 yields metallamacrocycles of formula [(HgI2)2(μ-L1)2] (1), [(HgI2)2(μ-L2)2] (2), [HgI2(μ-L3)]4 (3). In contrast, the reaction with L4 under the same conditions yields a coordination polymer of formula [{HgI2(L4)}]n (4). In addition, the X-ray structure of L2 is also reported. The influence of the flexibility of the ligand on the final shape and nuclearity of the macrocycle is also analysed. Hirshfeld surface analysis and fingerprint plots facilitate a comparison of intermolecular interactions in all compounds, which are crucial in the construction of the supramolecular architectures. Finally, some noncovalent interactions have been evaluated energetically using DFT calculations and characterized using Bader's theory of atoms-in-molecules. © The Royal Society of Chemistry 2017

Cis and trans isomers of 1-(5-bromothiophen-2-yl)-3-(10-chloroanthracen-9-yl)prop-2-en-1-one: synthesis and characterization

Chalcone derivatives are simple chemical scaffold found in natural products and have been extensively used as an effective template in medicinal chemistry for drug discovery. Two new geometrical isomers of 1-(5-bromothiophen-2-yl)-3-(10-chloroanthracen-9-yl)prop-2-en-1-one were synthesized, isolated and characterized by various spectroscopic techniques (FT-IR, NMR, LC-MS and UV-visible). Two different shaped ( cis and trans ) yellow colored single crystals were obtained by slow evaporation method and the molecular structures were confirmed by X-ray diffraction studies. The cis configuration crystallizes in the monoclinic P2(1)/c space group, whereas, trans configuration crystallizes in the orthorhombic P2(1)2(1)2(1) space group. The conformational changes lead to variations in molecular packing arrangement. In cis , 2-D layer-like architecture is constructed by C-H...O and S...S contacts, whereas, in trans 3-D zig-zag pattern is generated by C-H...O, C-H...Cl and Br...pi interactions. The unique supramolecular topology of the isomers established by diverse intra and intermolecular interactions was analysed by Hirshfeld surfaces, 2D fingerprint plots, 3D energy framework and NCI index model. The Frontier molecular orbitals explored HOMO-LUMO energy gap and associated electronic properties were calculated. The molecular electrostatic potential (MEP) was plotted to identify the reactive sites in the molecule. (C) 2021 Elsevier B.V. All rights reserved

The role of unconventional stacking interactions in the supramolecular assemblies of Hg(ii) coordination compounds

In this study, nine mercury(ii) complexes of the composition [Hg(Ln)(X)2] (X = Cl, Br and I, n = 1-3), (L1 = 2-pyridine piconyl hydrazone); L2 = (2-acetylpyridine piconyl hydrazone) and L3 = (2-phenylpyridine piconyl hydrazone) are synthesized and spectroscopically characterized. Single-crystal X-ray crystallography showed that the molecular complexes can aggregate into larger entities depending upon the anion coordinated to the metal centre. Moreover, Hirshfeld surface (HS) analyses were employed to gain additional insight into interactions responsible for the packing of complexes 1-9. Quantitative examination of 2D fingerprint plots revealed, among others, the dominating participation of H⋯H and H⋯X interactions in the molecular packing. Moreover, C-H⋯X hydrogen bonds, π-π, and chelate-ring-π interactions are described and analysed by means of density functional theory (DFT) calculations since they play an important role in the construction of three-dimensional supramolecular frameworks. The influence of the halide on the energetic features of the assemblies has been also studied. © The Royal Society of Chemistry

Chelate ring stacking interactions in the supramolecular assemblies of Zn(ii)and Cd(ii) coordination compounds: a combined experimental and theoretical study

The self-assembly of Zn(ii) and Cd(ii) ions with two isomeric tetradentate ligands, 2-pyridyl-isonicotinoylhydrazone (HL1) and 2-benzoylpyridyl-picolinoylhydrazone (HL2), was studied by elemental analysis, FT-IR spectroscopy and single-crystal X-ray diffraction. The reaction of zinc(ii) and cadmium(ii) salts with HL1 and HL2 in methanol under solvothermal conditions produced six monomer and one tetranuclear zinc(ii) complexes, namely, Zn(HL1)Br2 (1), Zn(HL1)Cl2 (2), [Cd(HL1)2](NO3)2·H2O (3), Cd(HL2)Br2(4), Zn(HL2)Cl2 (5), Zn(HL2)Br2 (6) and [Zn4(L2)4I2][ZnI4]·2H2O (7). The structure of 7 includes a cationic tetranuclear cluster of four zinc ions, four ligands, and two anions, counterbalanced by ZnI4 2− ions. However, the reaction of zinc(ii) and cadmium(ii) salts with HL1 under the same conditions produced monomer compounds. Herein, the ligand effects on the complex structures were studied. Hirshfeld surface analysis and fingerprint plots facilitate the comparison of intermolecular interactions in compounds 1-7, which are crucial in building supramolecular architectures. © The Royal Society of Chemistry