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Two new isostructural M(II) (M = Ni, Co) complexes with 2,2'-dipyridylamine (dipya) and dianion of terephthalic acid (H2tpht), [M(dipya)2(H2O)2](tpht) · 2H2O, have been synthesized by ligand exchange reaction and characterized by single-crystal X-ray diffraction, FTIR spectroscopy, TG/DSC analysis and magnetic measurements. The crystal structures of [M(dipya)2(H2O)2](tpht) · 2H2O consist of discrete complex units in which M(II) adopts deformed octahedral geometries. Two dipya ligands and two water molecules are coordinated to M(II) atom, tpht acts as a counter ion, while additional two water molecules remained uncoordinated. By numerous hydrogen bonds, all structural fragments are connected in three different chains which extend along [100], [010] and [001] directions, giving as a result a complex 3D network. The stabilization of 3D structure is accomplished by non-covalent face to face π-π interactions among pyridyl ring of dipya and benzene ring of tpht from adjacent chains. Towards the applied magnetic field, the both complexes exhibited almost perfect paramagnetic behavior. [ABSTRACT FROM AUTHOR]

A terephthalate-bridged heteronuclear Cu(II)-Mn(II) complex [Cu2Mn(dipya)2(tpht)3]n, I, where dipya is 2,2'-dipyridylamine and tpht is the anion of 1,4-benzenedicarboxylic (terephthalic, H2tpht) acid was synthesized under hydrothermal conditions. The obtained complex I was characterized by a single-crystal X-ray diffraction, FTIR spectroscopy, TG/DSC analysis and magnetic measurements. The Cu(II) and Mn(II) metal centers adopt distorted octahedral geometry and they are linked by bridging tpht ligands. Two crystallographically different tpht anions are coordinated as tridentate and hexadentate ligands forming two-dimensional layers. The layers are interconnected by hydrogen bonds and additionally stabilized by non-covalent C-H···π interactions. The measurements of magnetic susceptibility proved that I is an almost perfect paramagnet. [ABSTRACT FROM AUTHOR]

A series of new zinc complexes containing the 2,2′-dipyridylamine (dipya) ligand and anions of four benzenepolycarboxylic (BPC) acids, namely phthalic (H 2 pht), isophthalic (H 2 ipht), terephthalic (H 2 tpht) and pyromellitic (H 4 pyr), have been synthesized by ligand exchange reactions. The complexes were characterized based on elemental analysis, FTIR spectroscopy and thermal (TG/DSC) analysis. The complexes were found to have the formulae [Zn(dipya)(pht)] ( 1 ), [Zn(dipya)(ipht)] n ( 2 ), {[Zn(dipya)(tpht)]·H 2 O} n ( 3 ) and [Zn 2 (dipya) 2 (pyr)] ( 4 ). Compounds 2 and 3 have been obtained as single crystals and their crystal structures were determined from X-ray diffraction data. In both structures the coordination number of the Zn atoms is five and they are linked by bridging BPC ligands. In 2 , the ipht ligand is coordinated in a tridentate manner via chelate and monodentate COO groups, whereas two crystallographically different tpht ligands in 3 are coordinated as bis-chelate and bis-monodentate ligands, respectively. These combined modes of ipht and tpht anions resulted in zigzag chains of 2 and 3 . Two-dimensional pseudo-layers in 2 and a three-dimensional network in 3 are governed by hydrogen bonds and C–H⋯O interactions which are formed between the zigzag chains, and by additional C–H⋯ π interactions in 3 . The antimicrobial activity of complexes 1 – 4 was screened in vitro against some Gram-positive bacteria ( Bacillus subtilis , Enterococcus faecalis , Listeria monocytogenes and Staphylococcus aureus ), some Gram-negative bacteria ( Escherichia coli , Pseudomonas aeruginosa and Salmonella enteritidis ) and yeast Candida albicans . Complex 2 showed the most potent inhibitory effect against the tested microorganisms. [ABSTRACT FROM AUTHOR]

Four novel manganese(II) complexes with 2,2′-dipyridylamine (dipya) and various benzenedicarboxylate, BDC, ligands as anions of phthalic (pht), isophthalic (ipht) and terephthalic (tpht) acids were hydrothermally synthesized, namely, [Mn(dipya)(pht)(H 2 O)] 2 ( 1 ), [Mn(dipya)(ipht)] n ( 2 ), [Mn(dipya) 2 (tpht)] n ( 3 ), and [Mn(dipya)(H 2 O) 4 ](tpht) ( 4 ). All complexes were characterized by single-crystal X-ray diffraction, TG/DSC analysis and IR spectroscopy. The obtained complexes display a plenty of different structural features, including geometry of central metal atoms, BDC coordination modes and crystal packing. The coordination numbers of Mn(II) are different: 5 (in 2 ), 6 (in 3 and 4 ) and 7 (in 1 ). 3D networks in 1 – 4 are determined by strong non-covalent interactions. A survey of the Cambridge Structural Database for BDC complexes was performed in order to analyze orientation of COO groups. The energies of various BDC conformers were calculated by the second order Møller–Plesset perturbation theory and three hybrid HF/DFT methods with 6-311G ∗∗ basis set. To explain different behavior, BDC ions were also examined by Localized Molecular Orbital Energy Decomposition and Natural Bond Orbital analyses. Experimental and calculated geometries are in agreement, showing that tpht and ipht anions prefer the planar conformation, while in pht anions COO groups are inclined and make complementary angles relative to the aromatic rings. [ABSTRACT FROM AUTHOR]

The novel polymeric complexes catena-poly[[diaquamanganese(II)]-μ-2,2′-bipyrimidine-κ4 N1, N1′: N3, N3′-[diaquamanganese(II)]-bis(μ-terephthalato-κ2 O1: O4)], [Mn2(C8H4O4)2(C8H6N4)(H2O)4] n, (I), and catena-poly[[[aquacopper(II)]-μ-aqua-μ-hydroxido-μ-terephthalato-κ2 O1: O1′-copper(II)-μ-aqua-μ-hydroxido-μ-terephthalato-κ2 O1: O1′-[aquacopper(II)]-μ-2,2′-bipyrimidine-κ4 N1, N1′: N3, N3′] tetrahydrate], {[Cu3(C8H4O4)2(OH)2(C8H6N4)(H2O)4]·4H2O} n, (II), containing bridging 2,2′-bipyrimidine (bpym) ligands coordinated as bis-chelates, have been prepared via a ligand-exchange reaction. In both cases, quite unusual coordination modes of the terephthalate (tpht2−) anions were found. In (I), two tpht2− anions acting as bis-monodentate ligands bridge the MnII centres in a parallel fashion. In (II), the tpht2− anions act as endo-bridges and connect two CuII centres in combination with additional aqua and hydroxide bridges. In this way, the binuclear [Mn2(tpht)2(bpym)(H2O)4] entity in (I) and the trinuclear [Cu3(tpht)2(OH)2(bpym)(H2O)4]·4H2O coordination entity in (II) build up one-dimensional polymeric chains along the b axis. In (I), the MnII cation lies on a twofold axis, whereas the four central C atoms of the bpym ligand are located on a mirror plane. In (II), the central CuII cation is also on a special position (site symmetry ). In the crystal structures, the packing of the chains is further strengthened by a system of hydrogen bonds [in both (I) and (II)] and weak face-to-face π-π interactions [in (I)], forming three-dimensional metal-organic frameworks. The MnII cation in (I) has a trigonally deformed octahedral geometry, whereas the CuII cations in (II) are in distorted octahedral environments. The CuII polyhedra are inclined relative to each other and share common edges. [ABSTRACT FROM AUTHOR]

The present study describes representative examples of supramolecular arrangement of 5-phenylhydantoins achieved through various N–H⋯O hydrogen-bonding patterns. Four derivatives, 5-ethyl-5-(4-methylphenyl)hydantoin (1) and three 5-methyl-5-(3- or 4-substituted phenyl)hydantoins (2–4), were synthesized by the Bucherer–Bergs reaction and their crystal structures were determined by the single crystal X-ray diffraction method. A racemate, racemic hydrate and conglomerate as outcomes of crystallization from racemic solutions were found here. The crystal structures were firstly subjected to Hirshfeld surfaces analysis. The development of hydrogen bonding driven two-dimensional assemblies such as tapes, ribbons and sheets was further analysed using DFT calculations in terms of contribution of dimeric motifs as building blocks, which are associated with the presence of intermolecular interactions. To explore qualitative correlations between intermolecular interactions determining the crystal structures of the investigated compounds and those underlying their biological activity, we performed a docking study on the neuronal voltage gated sodium channels, matrix metalloproteinase 12 and aldose reductase. The supramolecular profiles of the investigated compounds are also maintained in biological systems and as such are responsible for differences in their biological activities. [ABSTRACT FROM AUTHOR]

Four novel polymeric iron(III) complexes with 2,2'-bipyridine (bipy) and different aromatic polycarboxylato ligands as anions of phthalic (pht), isophthalic (ipht), terephthalic (tpht) and pyromellitic (pyr) acid were synthesized by ligand exchange reaction. The complexes were characterized by elemental and TG/DSC analysis, FTIR and diffuse reflectance UV-Vis-NIR spectroscopy and magnetic susceptibility measurements. Based on the analytical and spectral data, the formulae of the complexes were {[Fe4(bipy)2(H2O)2(OH)6(pht)3]∙2H2O}n (1), {[Fe4(bipy)2(Hipht)2(ipht)2(OH)6]∙4H2O}n (2), {[Fe4(bipy)2(Htpht)2(OH)6(tpht)2]∙4H2O}n (3) and {[Fe4(bipy)(H2O)8- (OH)4(pyr)2]∙H2O}n (4). All complexes were red brown and low-spin with a distorted octahedral geometry with FeO6 or FeN2O4 chromophores. The polycarboxylato ligands played a bridging role in all cases, whereas monodentate COO groups were present in 2 and 3, while bridging and chelate COO groups were established in 1 and 4. The thermal behaviours of 1-4 were investigated in detail and the molar dehydration enthalpies were calculated. According to the all those results, the structural formulae of complexes 1-4 were proposed. [ABSTRACT FROM AUTHOR]

The title compound, (Hdipya)(H3pyr), where Hdipya is protonated 2,2'-dipyridilamine and H3pyr is the monoanion of pyromellitic acid (H4pyr), was obtained from a reaction mixture containing Zn(II) ions, dipya, Na4pyr (in the mole ratio 2:2:1) and HNO3. The products (micro- and single-crystalline) were characterized by X-ray structure determination, FT-IR spectroscopy and TG/DSC analysis. The most striking structural feature of (Hdipya)(H3pyr) are short inter- and extremely short intramolecular hydrogen bonds. These bonds mutually connect cations and anions making thin layers parallel to the crys-tallographic (223) plane. In addition, quite unusual, linear proton-bound polymeric {H(H2pyr)-}n were identified in the structure. The results of crystal structure determination are compared with FT-IR and TG/DSC data. The low position of the νas (COO) vibration at 1660 cm-1 is in accordance with strong hydrogen bonding. This value could be used as a measure of the C=O bond order, which was calculated to be 1.81. [ABSTRACT FROM AUTHOR]

Abstract: In this work, a combined experimental and theoretical study on the structures of methoxy substituted 5-phenylazo-3-cyano-1-ethyl-6-hydroxy-4-methyl-2-pyridones has been reported. The dyes under the investigation have been thoroughly characterized. X-ray single-crystal analysis shows that 5-(4-methoxyphenylazo)-3-cyano-1-ethyl-6-hydroxy-4-methyl-2-pyridone crystallizes in the hydrazone form. Quantum chemical calculations of energies, geometrical structure and vibrational wavenumbers of the investigated dyes have been performed using density functional theory. The optimized geometrical parameters obtained by density functional theory calculations are in good conformity with the single-crystal data. The fundamental vibrational wavenumbers, as well as their intensities have been calculated and a good agreement between observed and scaled calculated wavenumbers has been achieved. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital analysis. Vibrational, nuclear magnetic resonance and natural bond orbital analysis confirm that the prepared dyes exist in the hydrazone tautomeric form in the solid state and dimethyl sulfoxide solution. [Copyright &y& Elsevier]

The title compound, Rb2[Co(H2O)6](C8H5O4)4·4H2O, consists of nearly regular octahedral [Co(H2O)6]2+ cations with the CoII cations on the inversion centre (special position 2 a), Rb+ cations, hydrogen phthalate (Hpht−) anions and disordered water molecules. The Rb+ cation is surrounded by nine O atoms from Hpht− anions and water molecules, with a strongly deformed pentagonal-bipyramidal geometry and one apex split into three positions. The crystal packing is governed by numerous hydrogen bonds involving all water molecules and Hpht− anions. In this way, layers parallel to the ab plane are formed, with the aromatic rings of the Hpht− anions esentially directed along the c axis. While Hpht− anions form the outer part of the layers, disordered water molecules and Rb+ cations alternate with [Co(H2O)6]2+ cations in the inner parts. The only interactions between the layers are van der Waals forces between the atoms of the aromatic rings. A search of the Cambridge Structural Database for coordination modes and types of hydrogen-bonding interaction of the Hpht− anion showed that, when uncoordinated Hpht− anions are present, compounds with intermolecular hydrogen bonds are more numerous than compounds with intramolecular hydrogen bonds. For coordinated Hpht− anions, chelating and bridging anions are almost equally common, while monodentate anions are relatively scarce. The same coordination modes appear for Hpht− anions with or without intramolecular hydrogen bonds, although intramolecular hydrogen bonds are less common. [ABSTRACT FROM AUTHOR]

The article discusses a study on coordination polymer in the title as to structural diversity of the compounds and potentials. The N atoms and 3 O atoms from a di-2-pyridylamine (dipya) ligand formed a distorted pyramidal geometry of the CuII cation with the zigzag chains on the β axis. Findings indicated that metal-organic polymers are rare when benzene-1,3-dicarboxylate (ipht) is coordinated as bridging tridentate ligand with chelate and monodentate caboxylate.

Abstract: A series of novel ternary Co(II), Ni(II) and Cu(II) complexes containing 2,2′-dipyridylamine (dipya), 2,2′-bipyridine (bipy), and 1,10-phenanthroline (phen), as aromatic diamine ligands, and dianion of isophthalic acid (ipht) have been prepared by ligand exchange reactions from diluted H2O/EtOH solutions. The complexes were characterized by elemental analysis, IR spectroscopy, magnetic susceptibility measurements and TG and DSC analysis. Three complexes, Cu(dipya)(ipht)·H2O (1), Co(dipya)(ipht)·2H2O (2) and Cu(ipht)(phen)·2H2O (5) are polymeric with bis-monodentate ipht, while the other two complexes M(bipy)(ipht)·4H2O, Mce:bold>3) and Ni(II) (4), contain ipht as a counter ion. All Co(II) and Ni(II) complexes are (pseudo)octahedral, while Cu(II) complexes have square-pyramidal or distorted octahedral geometry. The variable temperature magnetic susceptibility measurements showed very weak antiferromagnetic behaviour for all complexes. Dehydration processes, decomposition mechanisms and thermal stability of 1–5 are assumed. One complex from the above series, [Ni(bipy)(H2O)4](ipht) (4), and one additional complex, [Co(bipy)(ipht)] n (6), are obtained as single-crystals and their structures are determined from X-ray diffraction data. In both structures M(II) centers are in deformed octahedral environment and they are linked by hemi-ipht ligands (4) and two different bridging ipht ligands (6). Three-dimensional networks in 4 and 6 are governed by strong noncovalent interactions. The cations and ipht anions in 4 are connected by hydrogen bonds building double layers parallel to ab-plane that are further packed by π–π interactions. In 6 double chains extending along b-axis are strengthened by interchain π–π interactions constructing a three-dimensional framework. [Copyright &y& Elsevier]

Thermal behaviour of a series of ternary Co(II), Ni(II) and Cu(II) complexes with terephthalate ion and some aromatic diamines has been studied by thermogravimetric and differential scanning calorimetric techniques. Dehydration processes of the complexes are very similar—most of them lose water in a single step. Thermal stability of the dehydrated products increases in the order Co for 2,2′-dipyridylamine and 2,2′-bipyridine containing complexes, but Cu for 1,10-phenanthroline containing complexes. The investigated compounds with 2,2′-bipyridine are always the most easily decomposed. The molar dehydration enthalpies are calculated and the possible decomposition mechanisms are assumed. Relations between thermal behaviour of the complexes and their crystal structures, type of central atom and aromatic diamine, as well as the presence of coordinated and/or lattice water molecules are discussed. [Copyright &y& Elsevier]

• A new spirohydantoin was synthesized and characterized. • A bilayer structure is formed via hydrogen bonds, C–H∙∙∙π, lp∙∙∙π and π∙∙∙π interactions. • The highest stabilization comes from the motif with the paired N–H∙∙∙O hydrogen bonds. • HOMO is mainly over the hydantoin and cyclohexyl rings; LUMO is on the benzoyl group. • The global reactivity descriptors indicate the soft nature of the molecule. Providing structural information on drug-like compounds is a significant step in efforts to develop innovative drugs with balanced solubility, cell permeability and target binding. In this paper, a new cyclohexane-5-spirohydantoin tethered with a 4‑tert-butylbenzoyl group was synthesized and its crystal structure was determined using the single crystal X-ray diffraction. The Hirshfeld surface analysis was used to gain a preliminary insight into the proportion and nature of the intermolecular interactions in the crystal structure, while their quantitative description is further presented in terms of a systematic analysis of dimeric motifs representing different recognition modes. A combination of N–H∙∙∙O and C(sp3)–H∙∙∙O hydrogen bonds, C(sp3)–H∙∙∙π, lone-pair∙∙∙π and π∙∙∙π stacking interactions links the molecules into a bilayer having two carbonyl O atoms exposed to the exterior. Further stacking of the bilayers occurs through C(sp3)–H∙∙∙O hydrogen bonds involving these O atoms as acceptors, C(sp3)–H∙∙∙π and π∙∙∙π stacking interactions between the phenyl groups. The molecular electrostatic potential surface map reveals that the carbonyl O atoms of the hydantoin ring and the phenyl ring are electrophilic centers, while the N1–H1 group is a nucleophilic center. The calculated HOMO and LUMO energies were used to semiquantitatively estimate the global reactivity descriptors suggesting the soft nature of the molecule. [Display omitted] [ABSTRACT FROM AUTHOR]

Zirconium carbide ceramics were prepared by carbothermal reduction of ZrO 2 and C that were mixed by high-energy ball milling. Powders were milled for times from 0 to 120 min in air. As milling time increased, the surface area of the powders increased, indicating significant particle size reduction. Milled powders were reacted at 1600 °C and then densified by spark plasma sintering at 2000 °C, which was sufficient to convert the starting powders to zirconium carbide. Unmilled powders did not reach full density. Milled powders reached full density, but ZrO 2 impurities were found for specimens prepared from powders milled for 60 and 120 min. Microstructure analysis showed that grain size was less than 2 µm for ceramics produced from powder milled for 15 min. Based on densification onset temperature and impurity levels, a milling time of 15 min gives the best balance of particle size reduction to promote densification while minimizing impurity levels. [ABSTRACT FROM AUTHOR]

In the search for environmentally friendly materials with a wide range of properties, polymer composites have emerged as a promising alternative due to their multifunctional properties. This study focuses on the synthesis of composite materials consisting of four components: bacterial nanocellulose (BNC) modified with magnetic Fe3O4, and a mixture of BaTiO3 (BT) and polyvinylidene fluoride (PVDF). The BT powder was mechanically activated prior to mixing with PVDF. The influence of BT mechanical activation and BNC with magnetic particles on the PVDF matrix was investigated. The obtained composite films' structural characteristics, morphology, and dielectric properties are presented. This research provides insights into the relationship between mechanical activation of the filler and structural and dielectric properties in the PVDF/BT/BNC/Fe3O4 system, creating the way for the development of materials with a wide range of diverse properties that support the concept of green technologies. [ABSTRACT FROM AUTHOR]

Two azo dye ligands, bearing different substituents (chlorine atom or methoxy group) in the para‐position of the phenyl ring, were employed for the synthesis of two Cu(II) chelates. Full structural affirmation of complexes was assessed. X‐ray diffraction measurements revealed that the coordination geometry for Cu atoms in both complexes is square‐pyramidal with a ligand:metal ratio of 2:1 where dyes behave as monobasic bidentate ligands. Thermogravimetric analyses of the complexes and their starting dyes were performed to study their thermal stabilities and decomposition behavior confirming the thermal stability of both dyes and complexes. Antioxidative activity of the complexes has been assigned and compared with their parent ligands revealing that the presence of the electron–donor, methoxy group, in the phenyl ring, in both dye and complex, is responsible for the activity (IC50 values of 1.54 for the dye and 1.30 mM for the complex). It should be stated that the complexation of the methoxy‐substituted dye leads to enhanced antioxidative activity concurrent to a standard antioxidant molecule of ascorbic acid, making this molecule a promising antioxidant agent. Docking study with vascular endothelial growth factor receptor 2 and Aurora kinase A proteins indicate that complexes exhibit higher binding affinities to proteins than the starting ligand dyes. The most promising structure exhibiting the best docking potential toward both proteins is the complex‐bearing methoxy group. The presented results represent a promising start for further investigations of these compounds as potential therapeutic candidates for the treatment of various types of cancer. [ABSTRACT FROM AUTHOR]

The peculiarities of sinter-crystallization of La 2 O 3 ·SrO·5B 2 O 3 fine glass powder (below 1 μm) are investigated and discussed. The sintering was studied by contactless optical dilatometry and porosity measurements. The crystallization process was evaluated by differential scanning calorimetry (DSC) and the crystalline phase formation was analyzed by X-ray diffraction (XRD). Finally the microstructures of the samples sintered at different temperatures were observed by field emission scanning electron microscope (FESEM). The specific aim of this study was to highlight the influence of sintering temperature and heating rate on the densification process and the final structure of glass-ceramic samples. It was shown that zero water adsorption and minimum closed porosity of ~ 3% were obtained at heating rate of 2 °C/min and at about 1 h holding at 690 °C. The temperature increase accelerated intense foaming process that resulted in formation of total porosity of 35–45%. It was also demonstrated that the foaming depended on the heating rate: the higher the heating rate – the more intensive was the bloating. The observed foaming process was related to intensive crystallization and re-crystallization of La 2 O 3 ·SrO·5B 2 O 3 crystal phase. The phase formation processes entirely completed after 30–60 min at 730–740 °C with the formation of intriguing and unusual crystal structures. [ABSTRACT FROM AUTHOR]

Thermal dehydration of two heterometallic complexes containing dianion of phthalic acid, pht, Na 2 [Cu(pht) 2 ] · 2H 2 O, 1 , and K 2 [Cu(pht) 2 ] · 2H 2 O, 2 , was investigated under non-isothermal conditions. Mechanism and kinetics of dehydration were analyzed in detail using TG/DSC/MS measurements, XRPD analysis and FT-IR spectroscopy. The reversibility of dehydration processes was identified. According to XRPD, dehydrated product of 1 maintains original structure, but dehydration of 2 undergoes structural transformation giving a dehydrated product of different crystal structure. In both cases dehydration process involves more than one elementary step, which was confirmed using isoconversional methods Deconvolution of this process using Fraiser-Suzuki function yielded two single step processes for 1 and 2 . Subsequent kinetic analysis was performed using Màlek algorithm, resulting in the determination of kinetic triplets ( E a , A and f(α) ) for each individual step. In addition, the dehydrated complexes were investigated as possible candidates for H 2 adsorption, using molecular simulations. [ABSTRACT FROM AUTHOR]

A biphasic [Mn(dipya)(H2O)4](tpht)/{[Zn(dipya)(tpht)]·H2O}n complex material, I (dipya = 2,2'-dipyridylamine, tpht2- = dianion of terephthalatic acid) was synthesized by ligand exchange reaction and characterized by XRPD and FTIR spectroscopy. A ZnO/ZnMn2O4 composite, II, has been prepared via thermal decomposition of I in an air atmosphere at 450 °C. XRPD, FTIR and FESEM analyses of II revealed the simultaneous presence of spherical nanoparticles of wurtzite ZnO and elongated nanoparticles of spinel ZnMn2O4. The specific surface area of II was determined by the BET method, whereas the volume and average size of the mesopores were calculated in accordance with the BJH method. The measurements of the mean size, polydispersity index and zeta potential showed colloidal instability of II. Two band gap values of 2.4 and 3.3 eV were determined using UV-Vis diffuse reflectance spectroscopy, while the measurements of photoluminescence revealed that II is active in the blue region of the visible spectrum. Testing of composite II as a pigmentary material showed that it can be used for the colouring of a ceramic glaze. [ABSTRACT FROM AUTHOR]

In search of novel photoactive liquid crystals, we have synthesized a series of five-ring pyridine-based bent-core compounds bearing different substituents at the peripheral phenyl rings (CH3O, Cl and NO2). Their mesomorphic behaviour has been investigated by polarizing optical microscopy, differential scanning calorimetry and X-ray scattering, and then compared with the unsubstituted parent compound. The introduction of the methoxy groups at the peripheral phenyl rings of the bent core results in a non-mesomorphic compound, whereas the chloro- and nitro-substituted compounds form enantiotropic B1-like phases. Significant changes in the textures and transition temperatures of the mesophase have been observed under UV light. The present investigation of the mesomorphic properties of the synthesized compounds, coupled with the analysis of the molecular packing of the related three-ring compounds, will help design self-organized molecules suitable for UV indicators. [ABSTRACT FROM AUTHOR]

This work examines two approaches for immobilization of lipase from Candida rugosa on oxidized multi-walled carbon nanotubes (o-MWCNTs). One method included the presence of activating agents to promote covalent bonding and the other the adsorption on o-MWCNTs to elucidate if non-specific bonding on the o-MWCNTs surface exists. The influence of the immobilization time and initial enzyme concentration on protein loading and the expressed lypolitic activity of the immobilized preparation were investigated. The results showed that the enzyme adsorbs on o-MWCNTs in a maximal amount of 37 μg mg −1 CNTs, while the attached amount was more than 2-times higher under covalent promoting conditions (80 μg mg −1 CNTs). Furthermore, similar trends were observed for the lypolitic activity, whereby preparations obtained under covalent promoting conditions had almost 3-times higher activity (560 IU g −1 of immobilized enzyme). In addition, immobilization of the enzyme was confirmed by Fourier transformation infrared spectroscopy and thermogravimetric analysis. [ABSTRACT FROM AUTHOR]

Thermal degradation of ternary transition metal complex containing tetraanion of pyromellitic acid, pyr, and ethylenediamine, en, [Ni( en)(HO)( pyr)]·4HO, 1, was investigated under non-isothermal conditions. The mechanism of thermal degradation, which occurs in three steps, was clarified by TG/DSC measurements in conjunction with FT-IR spectroscopy and XRPD analysis. The complexity of all degradation steps has been revealed using isoconversional methods. Dehydration comprises the loss of ten water molecules in a relatively narrow temperature interval, resulting in a very complicated reaction mechanism. In addition, density functional theory calculations have been applied for better understanding of dehydration. The second degradation step, related to loss of en, was separated into two single-step processes with Fraser-Suzuki function. The obtained individual steps were described by Johnson-Mehl-Avrami A2 model and Šesták-Berggren model, respectively. Validation of the proposed kinetic triplets for individual steps was performed using master plot and Pérez-Maqueda criteria. The third degradation step is related to the fragmentation of pyr ion most likely followed with the release of a number of gaseous products. [ABSTRACT FROM AUTHOR]

A Pd-Cu-Au/C nanocatalyst with a low content of Cu (8.2 at %) and Au (4.4 at %), and an average crystallite size of about 2 nm was synthesized by employing a one-pot two-steps borohydride reduction method in the presence of sodium citrate, characterized by energy-dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy and examined for the oxygen reduction reaction (ORR) in an alkaline solution. Pd/C and Pd-Cu/C catalyst with 17 at % Cu, which were synthesized by the same method, and a commercial Pt/C were used for comparison. In addition, Pd-Cu-Au/C and Pd-Cu/C nanocatalysts were treated in acid with a purpose of their dealloying. The electrochemically active surface area of Pd was determined from CO ads desorption. It was found that the ORR on all catalysts follows first order kinetics with respect to O 2 with four electrons transferred per O 2 molecule. The catalysts were subjected to a short-term cycling stability test. Pd-Cu/C and Pd-Cu-Au/C were more active for ORR than Pd/C and Pt/C. The acid-treated catalysts exhibited higher activity compared to their untreated counterparts; both initially and after the stability test (up to 1.7 times in specific activity and 2 times in mass activity). The catalyst with the highest specific and mass activity after the stability test was the acid-treated Pd-Cu-Au/C which surpassed Pd/C by a factor of up to 2.5 in specific activity and 5.7 in mass activity. It was concluded that the acid treatment leads to a major dissolution of Cu from the nanoparticles, thus leaving a highly disordered Pd structure exhibiting increased activity for the ORR, while Au stabilizes Pd structure contributing to better performance after the stability test. • Pd-Cu-Au/C nanocatalysts with a low content of Cu and Au was synthesized and tested for ORR in alkaline solution. • Pd-Cu-Au/C and Pd-Cu/C were treated in acid which resulted in dealloying of the nanocatalysts. • Acid-treated Pd-Cu-Au/C exhibited the highest specific and mass activity after the stability test. • Disordered Pd structure remained after the leaching of Cu is responsible for high activity. • Au stabilizes Pd structure and enables performance stability. [ABSTRACT FROM AUTHOR]

Two series of poly(e-caprolactone) poly(oxepan-2-one) nanocomposites with different organo-modified clays (1 to 8 wt. %) were prepared by the solution casting method. Organoclays with polar (Cloisite® C30B) and nonpolar (Cloisite® C15A) organic modifiers and with different miscibility with the poly(e-caprolactone) matrix were chosen. Exfoliated and/or intercalated structures of the nanocomposite were obtained using high dilution and ultrasonic treatment for the preparation of the composite. The effects of the surface modification and clay content on the morphology, and mechanical and thermal properties of the nanocomposites were studied. Scanning electron microscopy excluded the formation of microcomposites. The wide-angle X-ray diffraction analysis revealed that the tendency toward exfoliated structures was higher with Cloisite® C30B, which had better miscibility with poly(e-caprolactone) matrix, than with Cloisite® C15A. Differences in the sizes of the spherulites and morphology between two series of the nanocomposites were observed by optical microscopy performed on as-cast films. The enthalpies of fusion and degrees of crystallinity were higher for the nanocomposites than for the neat poly(ε-caprolactone) and increased with clay loading in both series, because of the nucleating effect of the clay. The decreased thermal stability of the nanocomposites was ascribed to the thermal instability of the organic modifiers of the clays. The Halpin-Tsai model was used to compare the theoretically predicted values of the Young's modulus with the ones experimentally obtained in tensile tests. [ABSTRACT FROM AUTHOR]

Two series of poly(ε-caprolactone) poly(oxepan-2-one) nanocomposites with different organo-modified clays (1 to 8 wt. %) were prepared by the solution casting method. Organoclays with polar (Cloisite® C30B) and nonpolar (Cloisite® C15A) organic modifiers and with different miscibility with the poly(ε-caprolactone) matrix were chosen. Exfoliated and/or intercalated structures of the nanocomposite were obtained using high dilution and ultrasonic treatment for the preparation of the composite. The effects of the surface modification and clay content on the morphology, and mechanical and thermal properties of the nanocomposites were studied. Scanning electron microscopy excluded the formation of microcomposites. The wide-angle X-ray diffraction analysis revealed that the tendency toward exfoliated structures was higher with Cloisite® C30B, which had better miscibility with poly(ε-caprolactone) matrix, than with Cloisite® C15A. Differences in the sizes of the spherulites and morphology between two series of the nanocomposites were observed by optical microscopy performed on as-cast films. The enthalpies of fusion and degrees of crystallinity were higher for the nanocomposites than for the neat poly(ε-caprolactone) and increased with clay loading in both series, because of the nucleating effect of the clay. The decreased thermal stability of the nanocomposites was ascribed to the thermal instability of the organic modifiers of the clays. The Halpin--Tsai model was used to compare the theoretically predicted values of the Young's modulus with the ones experimentally obtained in tensile tests. [ABSTRACT FROM AUTHOR]

Two spirohydantoin derivatives, 3-(4-chlorobenzoyl)-1,3-diazaspiro[4.5]decane-2,4-dione (1) and 3-(4-bromobenzoyl)-1,3-diazaspiro[4.5]decane-2,4-dione (2), were synthesized and analyzed by single crystal X-ray diffraction, DFT and QTAIM calculations. Simple substitution of the benzoyl unit gave rise to different crystal structures. In 1, a parallel stack along the b-axis with alternating perpendicular separation is formed, while in 2 the R 46 (32) nets are joined together to form stacks which enclose linear channels. Hierarchical development of these crystal structures was analyzed through dimeric motifs associated with the presence of intermolecular interactions. By including the previously reported structurally-related spirohydantoin derivatives, we created a set of structures which enabled us to evaluate substituent effects on their conformational preferences, i.e., widening of the dihedral angle between the hydantoin and substituted benzoyl unit when going from F to Br. A conformational search revealed that the value of the torsion angle N3–C11–C12–C13 can be regarded as a compromise between the extended conjugation between the carbonyl and phenyl group and intramolecular C–H⋯O interaction between these two groups. This intramolecular effect is more pronounced on the torsion angle C2–N3–C11–C12, which defines the relative orientation between the hydantoin ring and the carbonyl bridge. The present work may provide a basis for design of new cyclohexane-5-spirohydantoins with potential for pharmaceutical applications both at the molecular and supramolecular level. [ABSTRACT FROM AUTHOR]

Crystal structure of the title compound: [Cu 2 (bipy) 2 (pht) 2 ]·4H 2 O (bipy = 2,2'-bipyridine, pht = dianion of phthalic acid), CuBP·4H 2 O, consists of dinuclear entities, which are further connected by π–π stacking interactions between bipy ligands. In this way small channels (micropores) oriented parallel to the [0 0 1] direction and containing loosely hydrogen bonded water molecules are formed. The structural changes during dehydration–rehydration have been thoroughly investigated using TG/DSC analysis, FT-IR spectroscopy, X-ray powder diffraction, optical and scanning electron microscopy, and sorption experiments. In addition, dehydration process was analyzed from the aspect of kinetics. A complete reversibility of the dehydration–rehydration CuBP·4H 2 O(s) ⇌ CuBP(s) + 4H 2 O(g) process was confirmed by all means. Therefore, CuBP·4H 2 O can be classified as molecular sieve with quite unexpected zero-dimensional structure. [ABSTRACT FROM AUTHOR]

The quantitative assessment of intermolecular interactions and their cooperative effects has been performed in spirohydantoin-based model compounds, 3-benzoyl-1,3-diazaspiro[4.5]decane-2,4-dione (1) and 3-(4-fluorobenzoyl)-1,3-diazaspiro[4.5]decane-2,4-dione (2), through single crystal X-ray crystallography and quantum chemical studies. In both crystal structures, molecules generate the same hydrogen-bonded centrosymmetric R 22 (8) synthon. The extended supramolecular architectures depend on the C–H⋯O, C–H⋯π, stacking interactions and parallel interactions at large offsets, which lead to molecular sheets and further, with the assistance of the C–H⋯F interaction in the case of 2, to three-dimensional networks. Electrostatic potential maps have indicated that formation of the intermolecular F⋯F interaction in the crystal structure of 2 results in a new region with a larger surface area and a higher negative potential in comparison to the individual fluorine atoms. Establishment of this interaction leads to strengthening of the interaction of one of the fluorine atoms with a third molecule from the environment which does not interact with both of them. When this third molecule interacts with both fluorine atoms simultaneously, the calculations have shown that the effect of strengthening of the individual interactions due to formation of the F⋯F interaction is absent. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) nanoparticles were obtained by thermal decomposition of one-dimensional zinc-benzenepolycarboxylato complexes as single- -source precursors at 450 °C in an air atmosphere. The mechanism and kinetics of thermal degradation of zinc-benzenepolycarboxylato complexes were analyzed under non-isothermal conditions in an air atmosphere. The results of X-ray powder diffraction and field emission scanning electron microscopy revealed hexagonal wurtzite structure of ZnO with an average crystallite size in the range of 39-47 nm and similar morphology. The band gap and the specific surface area of ZnO nanoparticles were determined using UV-Vis diffuse reflectance spectroscopy and the Brunauer, Emmett and Teller method, respectively. The photoluminescent, photocatalytic and antimicrobial properties of the ZnO nanoparticles were also examined. The best photocatalytic activity in the degradation of C. I. Reactive Orange 16 dye was observed for the ZnO powder where the crystallites form the smallest agglomerates. All ZnO nanoparticles showed excellent inhibitory effect against Gram-positive bacterium Staphylococcus aureus and Gram-negative bacterium Escherichia coli. [ABSTRACT FROM AUTHOR]

A racemic spirohydantoin derivative with two aromatic substituents, a tetralin and a 4‐methoxybenzyl unit, was synthesized and its crystal structure was determined. To define the relationship between molecular stereochemistry and spatial association modes, development of the crystal packing was analyzed through cooperativity of intermolecular interactions. Homo and heterochiral dimeric motifs were stabilized by intermolecular N−H⋅⋅⋅O, C−H⋅⋅⋅O, C−H⋅⋅⋅π interactions and parallel interactions at large offsets (PILO), thus forming alternating double layers. The greatest contribution to the total stabilization came from a motif of opposite enantiomers linked by N−H⋅⋅⋅O bonds (interaction energy=−13.72 kcal/mol), followed by a homochiral motif where the 4‐methoxybenzyl units allowed C−H⋅⋅⋅π, C−H⋅⋅⋅O interactions and PILO (interaction energy=−11.56 kcal/mol). The number of the contact fragments in the environment of the tetralin unit was larger, but the 4‐methoxybenzyl unit had greater contribution to the total stabilization. The statistical analysis of the data from the Cambridge Structural Database (CSD) showed that this is a general trend. The compound is a potential inhibitor of kinase enzymes and antigen protein‐coupled receptors. A correlation between the docking study and the results of the CSD analysis can be drawn. Due to a greater flexibility, the 4‐methoxybenzyl unit is more adaptable for interactions with the biological targets than the tetralin unit. [ABSTRACT FROM AUTHOR]

Abstract Two series of cycloalkanespiro-5-hydantoins, namely cyclohexanespiro-5-hydantoins and cycloheptanespiro-5-hydantoins with a 4-substituted benzyl or a 2-(4-substituted phenyl)-2-oxoethyl group at N3 position, were synthesized and their effects on proliferation of human colon (HCT-116), leukemia (K562) and breast (MDA-MB-231) cancer cell lines were tested. For comparison, we also described the 5,5-diphenylhydantoin analogues. The structural features of the investigated compounds were characterized by elemental analysis, FT-IR, UV–Vis, 1H and 13C NMR spectroscopy and X-ray crystallography. Regarding their structure–activity relationships, it was shown that the substitution on the benzyl moiety with the methoxy, chloro or bromo group potentiated the antiproliferative activity relative to the parent compounds, while an increase in the size of the cycloalkyl group resulted mostly in a decrease of the antiproliferative activity. The single crystal X-ray analysis revealed the existence of dimers and chains formed by the N H⋯O hydrogen bonds. The analysis of the molecular descriptors of Lipinski demonstrated that all investigated compounds obeyed the rule of five. To further understand their geometry and electronic structure, DFT calculations with B3LYP method using 6-311++G(d,p) basic set were performed. In this context, the UV–Vis spectra of the investigated compounds were analyzed in detail, whereby the predicted absorption spectra from DFT calculation matched the experimentally obtained ones, with a good correlation. The interesting physico-chemical and pharmacologically relevant properties of the investigated compounds warrant their further investigation. Graphical abstract Image 1 Highlights • In searching for new hydantoin-based drugs, two series of compounds were synthesized. • Compounds with the CH 3 O, Cl or Br group exhibited an improved antiproliferative activity. • Different modes of intermolecular aggregation in the crystal structures were identified. • Substituent effects were reflected in the geometries and electronic structures. • The investigated compounds were compatible with the Lipinski rule of five. [ABSTRACT FROM AUTHOR]

A series of cycloalkane-5-spirohydantoins bearing a halogeno substituted benzyl group (X = Cl and Br) in position 3 has been synthesized and their structures (1–6) have been determined by a single crystal X-ray diffraction method. These compounds have multiple functional groups, which allow greater competition and/or cooperation among the different intermolecular interactions in the formation of their crystal structures. The molecules are linked together by paired N–H…O hydrogen bonds in R22(8) rings, while the C–H…O interactions lead to their further association into double chains. The contribution of the cycloalkyl ring depends on its conformational flexibility and the multiple C–H donor implications. In the case of compounds 1–4 bearing the cyclopentyl or the cyclohexyl ring, halogen bonding (X…O) interactions give rise to a supramolecular pseudo-hexagonal network. In addition, the C–H…X interactions with a higher degree of multifurcation at the halogen acceptor have an important role in the formation of the crystal structure. Regarding compounds 5 and 6 with the cycloheptane ring, the X…O interaction is absent, and along with the C–H…X interactions, these compounds realize an alternative crystal structure with an emphasis on the X…π interactions. The lattice energies of all these crystal structures, as well as the intermolecular pair energies, have been calculated using PIXEL and further partitioned into coulombic, dispersive, polarization and repulsive factors. The crystal structures have also been subjected to Hirshfeld surface analysis which reveals that approximately 75% of the close contacts correspond to relatively weak interactions. The application of both concepts has provided a new insight into the relationship between the molecular interactions and crystal structures of the hydantoin derivatives. [ABSTRACT FROM AUTHOR]

The structure-property relationship of newly synthesized 3-(4-substituted benzyl)-1,3-diazaspiro [4.4]nonane-2,4-diones was studied by experimental and calculated methods. The prepared compounds were characterized by UV-Vis, FT-IR, 1 H NMR and 13 C NMR spectroscopy and elemental analysis. The crystal structure was elucidated by single-crystal X-ray diffraction. The 3-benzyl-1,3-diazaspiro[4.4]nonane-2,4-dione crystallizes in triclinic P −1 space group, with two crystallographically independent molecules in the asymmetric unit. Cyclopentane ring adopts an envelope conformation. A three-dimensional crystal packing is governed by hydrogen N−H⋯O bonds, numerous C−H⋯O/N and C–H … π interactions between neighboring molecules. Density functional theory (DFT) calculations with B3LYP and M06-2X methods using 6–311++G(d,p) basis set were performed to provide structural and spectroscopic information. Comparisons between experimental and calculated UV-Vis spectral properties suggest that the monomeric form of the investigated spirohydantoins is dominant in all used solvents. The effects of substituents on the absorption spectra of spirohydantoins are interpreted by correlation of absorption frequencies with Hammett equation. The lipophilicities of the investigated molecules were estimated by calculation of their log P values. Some of the spirohydantoins synthesized in this work, exhibit the lipophilicities comparable to the standard medicine anticonvulsant drug Phenytoin. The results obtained in this investigation afford guidelines for the preparation of new derivatives of spirohydantoin as potential anticonvulsant agents and for better understanding the structure-activity relationship. [ABSTRACT FROM AUTHOR]

Pt nanoparticles supported on Vulcan XC-72R were synthesized by water-in-oil microemulsion method. By incorporating different amounts of HCl as a capping agent in the precursor-containing water phase, nanoparticle shape was varied. Influencing the growth of certain facets leads to the changes of the particle shape depending on the preferential facets. As a result, nanoparticles exhibit some of the electrochemical features typical for single crystals. Commonly employed synthesis procedure for water-in-oil microemulsion method was altered with the addition of catalyst support in the system and changing the catalyst cleaning steps. Prepared catalysts were characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and electrochemical methods. Activity and stability for methanol oxidation reaction (MOR), a structure-sensitive reaction, were tested. Electrochemical results reveal the influence of particle size, shape and exposed facets on the electrochemical processes. TEM investigations confirm electrochemical findings, while TGA verifies Pt loading in catalyst powder. Based on the results, optimal HCl concentration for cubic particle formation is determined, and structural effect on MOR activity and stability was tested. Cuboidal NPs show very good reaction activity and fair stability under applied experimental conditions. [ABSTRACT FROM AUTHOR]

The presented study investigates solidification/stabilization process of hazardous heavy metals/arsenic sludge, generated after the treatment of the wastewater from a primary copper smelter. Fly ash and fly ash with addition of hydrated lime and Portland composite cement were studied as potential binders. The effectiveness of the process was evaluated by unconfined compressive strength (UCS) testing, leaching tests (EN 12457-4 and TCLP) and acid neutralization capacity (ANC) test. It was found that introduction of cement into the systems increased the UCS, led to reduced leaching of Cu, Ni and Zn, but had a negative effect on the ANC. Gradual addition of lime resulted in decreased UCS, significant reduction of metals leaching and high ANC, due to the excess of lime that remained unreacted in pozzolanic reaction. Stabilization of more than 99% of heavy metals and 90% of arsenic has been achieved. All the samples had UCS above required value for safe disposal. In addition to standard leaching tests, solidificates were exposed to atmospheric conditions during one year in order to determine the actual leaching level of metals in real environment. It can be concluded that the EN 12457-4 test is more similar to the real environmental conditions, while the TCLP test highly exaggerates the leaching of metals. The paper also presents results of differential acid neutralization (d-AN) analysis compared with mineralogical study done by scanning electron microscopy and X-ray diffraction analysis. The d-AN coupled with Eh-pH (Pourbaix) diagrams were proven to be a new effective method for analysis of amorphous solidified structure. [ABSTRACT FROM PUBLISHER]

Abstract: In this study, the synthesis, structure and physical properties of two series of thermoplastic polyurethanes based on hydroxypropyl-terminated poly- (dimethylsiloxane) (HP-PDMS) or hydroxyethoxypropyl-terminated poly- (dimethylsiloxane) (EO-PDMS) as soft segments, and 4,4'-methylenediphenyl diisocyanate and 1,4-butanediol as hard segments were investigated. The polyurethanes were synthesized by two-step polyaddition in solution. The effects of the type and content of PDMS segments on the structure, thermal and surface properties of copolymers were studied by ¹H-, 13C-nuclear magnetic resonance (NMR) spectroscopy and two-dimensional NMR spectroscopies (heteronuclear multiple bond correlation (HMBC) and rotating-frame nuclear Overhauser effect (ROESY)), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), wide-angle X-ray scattering (WAXS), scanning electron microscopy (SEM) and water contact angle and water absorption measurements. Thermal properties investigated by DSC indicated that the presence of soft PDMS segments lowers the glass transition and melting temperatures of the hard phase as well as the degree of crystallinity. SEM analysis of the copolymers with a lower soft segment content confirmed the presence of spherulite superstructures, which arise from the crystallization of the hard segments. When compared with polyurethanes prepared from HP-PDMS, the copolymers synthesized from EO-PDMS with the same content of the soft segments had a higher degree of crystallinity, better thermal stability and a less hydrophobic surface. The obtained results showed that the synthesized polyurethanes had good thermal and surface properties, which could be further modified by changing the type or content of the soft segments. [ABSTRACT FROM AUTHOR]

Highlights: [•] The epoxy/clay Cloisite 30B NCs were prepared by the solution intercalation method. [•] A mainly exfoliated structure changed to intercalated one by increasing clay content. [•] NC with 1wt% clay exhibited the best corrosion resistance in 3% NaCl solution. [•] In salt spray tests the coatings with 1–3wt% clay showed anticorrosive improvements. [ABSTRACT FROM AUTHOR]

• Polymeric Co(II) complex with anion of H 6 mell was synthesized and characterized. • 3D supramolecular network is comprised of supramolecular and water layers. • Contribution of noncovalent interactions and their energies were determined by DFT. Orange single crystals of new polymeric cobalt(II) complex {[Co(bipy)(H 2 O) 4 ] 2 [Co(μ-mell)(H 2 O) 2 ]·10H 2 O} n , 1 , were synthesized by slow evaporation method at room temperature (bipy = 2,2′-bipyridine, mell = hexaanion of mellitic acid) and its crystal structure was determined by single-crystal X-ray diffraction. The complex 1 was characterized based on elemental analysis, FTIR spectroscopy and thermal (TG/DTA) analysis followed by computational analysis of noncovalent interactions and quantum chemical calculations of interaction energies. In 1 , two crystallographically different Co(II) atoms adopt a deformed octahedral geometry, while bridging mell acts as a tetrakis monodentate ligand allowing the development of wavy-like anionic chains running along [100] direction. The 3D supramolecular network of 1 is composed of alternating supramolecular and water layers connected by hydrogen bonds. The supramolecular layer is formed of ionic interactions between complex cations and polymeric complex anions, established mainly through O–H···O hydrogen bonds, as well as stacking interactions between bipy ligands, while the water layers are comprised of hydrogen bonded lattice water molecules. Upon heating up to 1200 °C in nitrogen and air atmosphere, complex 1 showed multiple-step degradation that resulted in the formation of Co and Co 3 O 4 , respectively. Computed Hirshfeld surfaces and 2D fingerprint plots indicated that O–H···O hydrogen bonds are the most dominant in the crystal structure, while the shape index and curvedness mapped on the Hirshfeld surfaces of 1 revealed that stacking interactions have an important role in the stabilization of the crystal packing. Quantum chemical calculations showed that, aside from ionic hydrogen-bonded interaction between cation and anionic polymer, the important role in the stability of supramolecular structure of 1 is played by hydrogen bonds of cation and anionic polymer with lattice water, as well as by stacking interactions between bipy ligands. The 3D supramolecular network of a polymeric {[Co(bipy)(H 2 O) 4 ] 2 [Co(μ-mell)(H 2 O) 2 ]·10H 2 O} n complex is composed of alternating supramolecular and water layers connected by hydrogen bonds. According to the quantum-chemical studies, the hydrogen bonds are the most dominant, while stacking interactions contribute to stabilization of the crystal packing of the complex. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: A series of polycrystalline samples containing sillenite-like (doped γ-Bi2O3) phases were prepared by high-temperature reactions from α-Bi2O3 powder and different oxides in six pseudo-binary Bi2O3–M x O y (M = Mn, Ti, V) and six pseudo-ternary Bi2O3–M1 x O y –M2 x O y (M1 = Pb, Zn, Ti and M2 = Zn, Ti, Si) systems. The products were characterized by XRD, SEM/EDX, HRTEM, SAED and DTA techniques. It is shown that for pseudo-binary systems, the phase composition of specimens depends on dopant content, while, for pseudo-ternary systems, depends on dopants radii, as well. In pseudo-binary systems, single-phase sillenites are obtained if the dopant content is in accordance with formula Bi12M4+O20, for M = Mn and Ti, and , for M = V. However, two coexisting sillenite-like phases, doped compound and nominally undoped solid solution, are found if a half of that dopant quantity is applied. In pseudo-ternary systems, the phase-pure double-doped sillenite specimens are identified if ionic radii of dopants differ less than 40%. Otherwise, two coexisting sillenites were obtained. The possibility to prepare the undoped γ-Bi2O3 phase was also discussed. [Copyright &y& Elsevier]

Segmented poly(urethane-urea-siloxane)s (PUUS) were synthesized using 4,4′-methylenediphenyl diisocyanate (MDI) and ethylene diamine (ED) as the hard segment components and hydroxypropyl-terminated poly(dimethylsiloxane) (PDMS) as the soft segment component, where the hard segment content ranged from 38 to 65 wt%. Segmented PUUSs were prepared by a two-step polymerization procedure in tetrahydrofuran/ N-methylpyrrolidone (THF/NMP) mixture with a large proportion of polar solvent. The structure, composition and hard segment length were determined by C NMR and two-dimensional correlation spectroscopy. Thermal, mechanical, small-angle X-ray scattering and hydrogen bonding analyses indicated the formation of the microphase-separated copolymers with high tensile strength. Globular superstructures observed in the copolymer films by scanning electron microscopy (SEM) and atomic force microscopy (AFM) were probably arisen from the microstructural organization of the MDI-ED segments, depending on their content and length. The PUUS copolymers showed high water resistance and became more hydrophobic with increasing weight fraction of PDMS. [ABSTRACT FROM AUTHOR]

Abstract: Alumina nanofibers are very suitable materials for use as reinforcement in a great variety of high performance composite materials. Nanosized alumina fibers were prepared from the aluminum chloride hydroxide/poly (vinyl alcohol)/water precursor using the electrospinning technique. The mass ratio of aluminum chloride hydroxide/polymer was 5/1. The fibers were calcinated at 1100°C. The fibers were characterized by the TGA/DTA, XRD and FESEM methods. Calcinated fibers had a mean diameter of 470nm and corundum well defined crystal structure. [Copyright &y& Elsevier]

Abstract: In this study, the synthesis of biodiesel or fatty acid methyl esters (FAME) from sunflower oil and methanol using CaO·ZnO catalyst was investigated. Catalyst was synthesized by ball milling of Ca(OH)2 and ZnO powder mixture with the addition of water (BMH), as well as solely by ball milling of mentioned powders (BM) and subsequent calcination at 700°C in air atmosphere. For comparison, the CaO·ZnO mixed oxide was also prepared using usual coprecipitation procedure (CP) followed by calcination at 700°C of the formed calcium zinc hydroxide hydrate. The BMH, BM and CP catalysts were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), infrared spectroscopy (FTIR), particle size distribution measurement and scanning electron microscopy (SEM and SEM-EDS). In addition, specific surface area (BET), solubility in methanol at 60°C and alkalinity (Hammett indicator method) were also determined. The activity of BMH, BM and CP catalysts for biodiesel synthesis were tested at 60°C and 1bar, using molar ratio of sunflower oil to methanol of 1:10 and with 2wt% of catalyst based on oil weight. [Copyright &y& Elsevier]

Carbon-supported Pt and Pt-Rh-Sn catalysts were synthesized by the microwave-polyol method in ethylene glycol solution and were investigated in the ethanol electro-oxidation reaction. The catalysts were characterized in terms of structure, morphology and composition employing the X-ray diffraction (XRD), scanning tunneling microscopy and energy-dispersive X-ray spectroscopy techniques. The STM analysis indicated rather uniform particles and particle sizes below 2 nm for both catalysts. The XRD analysis of the Pt/C catalyst revealed two phases, one with the main characteristic peaks of the face--centered cubic crystal structure (fcc) of platinum and the other related to the graphite-like structure of the carbon support, Vulcan XC-72R. However, in the XRD pattern of the Pt-Rh-Sn/C catalyst, diffraction peaks for Pt, Rh or Sn could not be resolved, indicating extremely low crystallinity. The small particle sizes and homogeneous size distributions of both catalysts could be attributed to the advantages of the microwave-assisted modified polyol process in ethylene glycol solution. The Pt-Rh-Sn/C catalyst was highly active for ethanol oxidation with the onset potential shifted by more than 150 mV to more negative values and with currents nearly 5 times higher in comparison to the Pt/C catalyst. The stability tests of the catalysts, as studied by chronoamperometric experiments, revealed that the Pt-Rh-Sn/C catalyst was evidently less poisoned than the Pt/C catalyst. The increased activity of Pt-Rh-Sn/C in comparison to Pt/C catalyst was most probably promoted by the bi-functional mechanism and the electronic effect of the alloyed metals. [ABSTRACT FROM AUTHOR]

Abstract: Bentonite samples collected from vicinity of Petrovac and Aleksinac were treated with different sulfuric acid molarities. Acid attack dissolved the octahedral sheets by interlayer and edge attack. The effects of the H2SO4 acid caused an exchange of Al3+, Fe3+ and Mg2+ with H+ ions leading to a modification of the smectite crystalline structure. The Mg and Fe substitution in the octahedral sheets promoted the dispersion of corresponding layers and formation of amorphous silicon. The activated bentonites, after the treatment of sulfuric acid, exhibited a lower cation-exchange capacity (CEC) and significant increase of specific surface area from 6 to 387m2 g−1 (bentonite from Petrovac) and from 11 to 306 m2 g−1 (bentonite from Aleksinac). The acid reaction caused a splitting of particles within the octahedral sheet which led to an increase in specific surface area and decrease in CEC in both bentonites. [Copyright &y& Elsevier]

Abstract: Multi-walled carbon nanotubes (MWCNTs) were used as a support for Pt nanoparticles prepared by the microwave-assisted polyol method. The MWCNTs were pretreated by chemical oxidation (o-MWCNTs) followed by modification by ethylenediamine (eda-MWCNTs). Characterization of both oxidized and eda-modified materials by UV-spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy revealed that the modification by eda leads to (i) agglomeration of the MWCNTs, (ii) a decrease in the capacitance of the material and (iii) reduced rate of electron transfer between the MWCNTs and solution species. However, the Pt loading of Pt/o-MWCNTs was only 2mass% while the loading of Pt/eda-MWCNTs was 20mass%. Much higher efficiency of Pt deposition on eda-MWCNTs than on o-MWCNTs was ascribed to the shift in pHpzc value of the MWCNT surface from 2.43 to 5.91 upon modification by eda. Transmission electron microscopy revealed that the mean diameter of the Pt particles in Pt/eda-MWCNTs is 2.5±0.5nm and that their distribution on the support is homogenous with no evidence of pronounced particle agglomeration. Cyclic voltammetry of a Pt/eda-MWCNT thin film indicated a clean Pt surface with well-resolved peaks characteristic of polycrystalline Pt. Its electrocatalytic activity for oxygen reduction was examined and the results corresponded to the commercial Pt nanocatalyst. This study shows that modification of o-MWCNTs by eda helps to achieve homogenous distribution of small Pt nanoparticles and does not impede its electrocatalytic activity. [Copyright &y& Elsevier]

The crystal structure of the complex [Ni2(btc)dipya)2(H2O)6·6H2O·DMSO (btc = tetra-anion of 1,2,4,5-benzenetetracarboxylic acid, dipya = 2,2'-dipyridylamine was refined in the triclinic system, space group P1--, using low temperature (170 K) X-ray diffraction data. The compound consists of binuclear complex entities and lattice solvent molecules making pseudo-layers parallel to the 101 plane and channels parallel to the b-axis. The observed structural features were compared with the previously reported results and formula [Ni2(btc)(dipya)2(H2O)6]·4H2O based on room temperature X-ray diffraction data. A possible arrangement of the disordered lattice solvent molecules located in the structural channels is described and discussed. It is concluded that the layout of these molecules is non-centrosymmetric, although the remaining and main part of the structure is centrosymmetric. [ABSTRACT FROM AUTHOR]

• Hydrated zwitterionic crystals of pyridone derivatives have been obtained. • Water and zwitterions interlocked into crystal packing through an interplay of interactions. • By coupling the experimental and calculated data of crystal structure, packing is elucidated. • The architecture depends on the number of water molecules and the nature of interactions. Two pyridone derivatives, bearing the pyridinium moiety (1), or dimethylpyridinium moiety (2), have been synthesized and their crystal structures have been determined. The compounds crystalize in hydrated zwitterionic forms with either two (1·2H 2 O) or four (2·4H 2 O) water molecules. The zwitterionic networks contain different types of water clusters, generated into channels, incorporating them into the network by sandwiching. The type of channel depends on the crystal lattice and the nature of non-covalent interactions established between zwitterions as well as the number of water molecules incorporated into the architecture. 1 affords tubes filled in with water channels formed by water tetramers, contrary to 2 , which affords a layered network altering the zwitterionic layer and the layer formed by water tetramers and hexamers. A detailed study of intermolecular interactions of both crystal structures and a quantification of interaction energies has been performed using PIXEL lattice energy calculations, giving an insight to a quantitative evaluation of interactions through Coulombic, disperse, repulsion and polarization energies. The strongest pairwise, in both structures, is found to be a dipole–dipole interaction between oppositely charged heterocyclic rings. The differences in the crystal packings of these hydrates have been elucidated by the fingerplot analysis. The comparative studies between experimental and calculated (DFT) data of molecules 1·H 2 O and 2·4H 2 O for systems of different complexity are performed. Furthermore, correlations of experimental and calculated bond lengths and the simulation of compound solvation with the CPCM model are done. [Display omitted] [ABSTRACT FROM AUTHOR]

Title compounds of type (VI) are prepared and tested as potential anticonvulsant agents. [ABSTRACT FROM AUTHOR]