Vol 87, No 11 (2017)
- Year: 2017
- Articles: 39
- URL: https://journals.rcsi.science/1070-3632/issue/view/13685
Article
Formation of nanocrystalline BiFeO3 under hydrothermal conditions
Abstract
The formation of bismuth orthoferrite under hydrothermal conditions at temperature 160, 180, or 200°С and pressure 100 MPa in aqueous solution of potassium hydroxide has been studied. The determined composition and structure of polycrystalline phase with sillenite structure have evidenced its formation at the interface of the crystallites of amorphous iron oxide. It has been shown that the formation of polycrystalline round-shaped BiFeO3 particles with size about 20 μm occurs via aggregation of perovskite-type phase crystallites (38–70 nm). Pycnometric density of BiFeO3 and the amorphous phase has been determined, and Mossbauer spectra reflecting the state of iron in the phases coexisting during the formation of BiFeO3 have been analyzed.
The formation of nanocrystalline orthoferrites of rare-earth elements XFeO3 (X = Y, La, Gd) via heat treatment of coprecipitated hydroxides
Abstract
Heat treatment of coprecipitated hydroxides in air has afforded isometric nanocrystals of rhombic yttrium, lanthanum, and gadolinium ferrites with average crystallite size 40±4 nm. It has been stated that the formation of XFeO3 (X = Y, La, Gd) nanocrystals occurs via two mechanisms, from the corresponding coprecipitated hydroxide (main route) and from the products of partial carbonatization of the precursor (side route). It has been shown that the formation of XFeO3 (X = Y, La, Gd) nanocrystals via the main and the side routes occurs at 500 and 780°С (o-YFeO3), 646 and 900°С (o-LaFeO3), and at 769°С (o-GdFeO3). Basing on the obtained data, we have suggested a scheme of chemical and physical transformations accompanying the formation of nanocrystals of yttrium, lanthanum, and gadolinium ferrites.
Structure, magnetic, and electrical properties of bismuth niobates doped with d-elements: XVIII. Magnetic susceptibility and ESR spectra of Bi2BaNb2–2xMn2xO9–δ solid solutions with layered perovskite-like structure
Abstract
On the basis of the data of ESR and magnetic susceptibility of Bi2BaNb2–2xMn2xO9–δ solid solutions with perovskite-like structure ferro- and aniferromagnetic bonded dimers, trimers, and tetramers of Mn(II), Mn(III), and Mn(IV) atoms in various valence states were found. The distribution of aggregates and exchange parameters in the clusters were calculated as a function of fraction x of manganese atoms in the solid solutions. In the ESR spectra of diluted solid solutions there are absorption bands with g-factors ~4.3 and 2.1 assigned to Mn(II) and Mn(IV) atoms.
Oxidative decomposition of oxalate ion with ozone in aqueous solution
Abstract
The oxidation of oxalate ions with ozone in aqueous solution has been studied, and the effects of pH, temperature, and reactant concentrations on the reaction rate and efficiency have been estimated. The oxidative decomposition is most effective in alkaline medium (pH ≥ 10) at 50°C. Under these conditions, the consumption of ozone is 0.6±0.1 g per gram of oxalate or 1.1±0.1 mol per mole of oxalate, which corresponds to the stoichiometry (COO–)2 + O3 + H2O → 2CO32– + O2 + 2H+.
Rhodium(I) bisaldimine complexes in transfer hydrogenation
Abstract
The reactions of hydrogen transfer from 2-propanol on acetophenone in the presence of the system [Rh(cod)Cl]2–L] (L is bisaldimine ligands based on (R,R)-1,2-cyclohexanediimine and pyridine-, quinoline-, and thiophenecarboxaldehyde) were studied. Rhodium(I) complexes with optically active ligand showed a high catalytic activity (up to 345 h–1) and moderate enantioselectivity [up to 55% ee of (R)-1-phenyethanol]. The structure of rhodium complex with N,N'-(1R,2R)-cyclohexane-1,2-diyl-bis[1-(pyridine-2-yl)methanimine] was determined on the basis of the data of 1H and 13C NMR spectroscopy and quantum chemical calculations.
Colloid and nanosized catalysts in organic synthesis: XVII. Reductive amination of carbonitriles in the presence of supported nickel nanoparticles
Abstract
Reductive amination of carbonitriles catalyzed by nickel nanoparticles applied onto a solid support in a plug flow reactor in the gas phase or the gas–liquid–solid catalyst system occurs at atmospheric pressure of hydrogen affording the nonsymmetrical secondary or tertiary amines. The effect of the support type on the target product yield and conversion of the substrate has been studied.
Cross effects of structure and temperature in the reactions of trans-2,3-diaryloxiranes with arenesulfonic acids
Abstract
Cross effects of the reagent structure and the temperature on the rate and activation parameters of the reactions of symmetrically X-substituted trans-2,3-diaryloxiranes with Y-substituted arene-sulfonic acids have been investigated in the temperature range 265–298 K. The isokinetic temperature of 265 K was reached, at which the rate and the free energy of the ring-opening reaction of trans-2,3-bis(3-bromo-5-nitrophenyl)-oxirane practically do not depend on substituent Y. The transition through the isoparametric points on substituent Y was realized with the inversion of the temperature effect on the free energy of activation for the reactions of oxiranes with X = 4-NO2 and 3-Br-5-NO2.
Cyclohexane in nanotubes: Direct chair–chair interconversion
Abstract
DFT PBE/3ζ study of conformational transformations of cyclohexane inside nanotubes with chirality indices of (8,0) and (5,5) showed that the encapsulated molecule is characterized by shortened C–C bonds, some electric charge, and reduced barrier to chair–chair interconversion in comparison to the free molecule. Unlike free cyclohexane, no twist conformer as intermediate minimum on the potential energy surface was localized for the encapsulated molecule.
Synthesis of aminomethyl derivatives of phosphonocarboxylates of the furan series
Abstract
By reaction of halomethyl derivatives of phosphonocarboxylates of the furan series with sodium azide corresponding azidomethyl compounds were synthesized. Treating them with triphenylphosphine in ethanol results in primary amines. Seven of the twelve possible position isomers of the aminomethyl phosphonocarboxylates were obtained. Method was found of selective dealkylating phosphonates leaving intact the ester group present in the molecule.
Synthesis, complexing properties, and selectivity of bis(diphenylphosphorylmethyl) ethers of oligoethylene glycols. Crystal structure of 1,3-bis(diphenylphosphoryl)-2-oxapropane
Abstract
A convenient method of synthesis of phosphoryl-substituted podands with dipehnylphosphorylmethyl end groups of the general formula Ph2P(O)CH2O(CH2CH2O)nCH2P(O)Ph2 (Ln, n = 0–6) is described. The stability constants of the complexes of the podands with alkali metal 2,4-dinitrophenolates were determined by conductometry. The ion-selective properties of the podands with respect to alkali and alkaline-earth metal cations were assessed by ionometry. The crystal structure of 1,3-bis(diphenylphosphoryl)-2-oxapropane was established by X-ray diffraction analysis.
Compounds of potassium and tin(II) with diiminopyridine ligands: EPR spectroscopy and theoretical study
Abstract
Potassium and tin(II) derivatives of the paramagnetic forms of the redox-active 2,6-bis(2,6-diisopropylphenyliminomethyl)pyridine were synthesized and studied by means of EPR spectroscopy. It was shown that the reaction with metallic potassium involves the three-electron step reduction of the organic ligand to form a radical anion, dianion, and trianion radical, respectively. The reactions of the tin(II) diiminopyridine derivatives with metallic magnesium give complexes comprising the radical anion form of the ligand and a low-valence metal center. The geometries of the paramagnetic products and their spin density distributions were explored in terms of the density functional theory.
Synthesis and 31P NMR study of chromium, molybdenum, and palladium complexes with 9-substituted 1,2-bis(diphenylphosphanyl)-o-carboranes
Abstract
9-Substituted 1,2-bis(diphenylphosphanyl)-o-carboranes were synthesized from the corresponding 9-R-o-carboranes (R = I, i-Pr, SMe), and their complexes with chromium, molybdenum, and palladium were obtained. The coordination chemical shifts calculated from the 31P NMR spectra of the complexes and free ligands showed that the substituent at B9 of carborane affects the strength of the ligand-to-metal binding, but the latter is determined to a greater extent by the nature of the metal and its ligand environment.
Synthesis and structure of trimethylantimony dimethacrylate
Abstract
The reaction of trimethylantimony with methacrylic acid in the presence of tert-butyl hydroperoxide gave trimethylantimony dimethacrylate Me3Sb(O2CCMe=CH2)2 whose structure was confirmed by elemental analysis and IR, 1H and 13C NMR, and mass spectra. According to the X-ray diffraction data, the title compound is a trigonal–bipyramidal antimony complex with three methyl group in the pyramid base and two methacrylate ligands in the apices.
On the mechanism of cobalt(III) aminates pyrolysis
Abstract
Pyrolysis of the complex (ato-N2)pentaammincobalt(III) perchlorate and the ligand 5-nitrotetrazole, and also of the initial complex aquapentaammincobalt(III) perchlorate was studied by the mass spectroscopy method. The leading oxidizer of ligands in the complexes is changed for the outer-sphere perchlorate ion at the pyrolysis temperature of ~250°C.
Low-temperature equilibriums in solutions of isocyanide-phosphine complexes of palladium(II) chloride
Abstract
cis-[PdCl2(CNR)(PPh3)] [R = Cy, t-Bu, C(Me)2CH2C(Me)3] have been synthesized via the interaction of [(PPh3)ClPd(μ-Cl)2PdCl(PPh3)] with isocyanide in CH2Cl2 at room temperature with 90–98% yield and characterized by means of mass spectrometry as well as 1H, 13C{1H, 31P}, and 31P{1H} NMR spectroscopy. The complexes structure in the solid phase has been elucidated by means of X-ray diffraction analysis. Dynamic processes in the solutions of the complexes in CDCl3 and CD2Cl2 at temperature of–95 to 60°С have been studied by means of 1H and 31P NMR spectroscopy. It has been found that the studied compounds existed exclusively in the cis-[PdCl2(CNR)(PPh3)] form in the solutions. In the case of cis-[PdCl2(CNCy)(PPh3)] in CH2Cl2, the conformational transitions of the equilibrium forms (the transition of the substituent in the cyclohexyl cycle between the equatorial and axial positions) are slowed down, the equatorial conformer prevailing in the solution (2: 1 at–95°С). Quantum-chemical simulation (DFT) has revealed that the standard Gibbs energy of the conformational transition from the axial form of cis-[PdCl2(CNCy)(PPh3)] into the equatorial one in the CH2Cl2 solution at 178 K equals–2.5 kJ/mol, being in agreement with the experimental data.
Synthesis, X-ray analysis, and quantum-chemical DFT study of features in formation of a binuclear phenanthroline complex with a VIV–O–VV core
Abstract
A new mixed-valence complex [(O)(phen)2VIV(μ-O)VV(O)phen)(mal)]+ was synthesized and characterized by the X-ray structural analysis. Its geometric structure was simulated by the DFT M06/6-31G(d,p) method. Comparison of calculated and experimental data made it possible to draw a conclusion on the oxobridging nature of the bond between vanadium fragments and to confirm the value of the target compound charge. The energy characteristics of cation formation reactions in solution were estimated. It was found that the oxidation of VIV to VV assists subsequent substitution of ligands. Joining [(O)VIV(phen)2]2+ and [(O)VV(O)(phen)(mal)]– particles proceeds by the donor-acceptor mechanism.
Complexes of 1-alkyl-4-aza-1-azoniabicyclo[2.2.2]octane bromides with lanthanum nitrate. Micelle-forming and adsorption properties
Abstract
Novel organometallic surfactants were synthesized from monoquaternized 1,4-diazabicyclo[2.2.2]-octanes of varied hydrophobicity [Alk = CnH2n+1, n = 14, 18] and lanthanum nitrates. The spectral, micelleforming, and adsorption properties of the synthesized compounds were studied by IR, 1Н NMR and electronic spectroscopy, tensiometry, conductometry, and potentiometry. The critical micelle concentrations, counterionic micellar binding constants, and adsorption parameters at the water–air interface were determined and compared with the respective characteristics of the ligands and conventional amphiphiles.
Molecular machines as a driving force of progress in modern post-industrial society
Abstract
The review considers main advances achieved in recent years in a fairly old and simultaneously modern field of research, controlled motion at the molecular level and its practical transformation in the form of synthetic molecular machines and devices. The basic principles of the design and controlled linear and rotational motion in such molecular systems and various useful functions potentially inherent in synthetic molecular machines have been discussed. Examples of already implemented molecular rotors, shuttles, switches, transporters, and muscles are given. Finally, immediate and more distant prospects for the development of this fascinating and very important field of nanotechnology are presented.
Novel approach to the synthesis of istaroxime
Abstract
Istaroxime 1, a novel cardiotonic agent with high efficiency and low toxicity was synthesized from dehydroepiandrosterone 2 using a novel approach that included epoxidation, ring-opening, substitution, and oximation. The new protocol without gas protection was milder than the reported approaches. The overall yield of the method was 24.1%.
Synthesis and antimicrobial activity of novel substituted 4-[3-(1H-benzimidazol-2-yl)-4-hydroxybenzyl]-2-(1H-benzimidazol-2-yl)phenol derivatives
Abstract
A series of novel substituted bis-benzimidazole derivatives were synthesized by reaction of 5,5′-methylenebis(2-hydroxybenzaldehyde) with various substituted o-phenylenediamines in glacial acetic acid. The structure of the newly synthesized compounds was elucidated by 1H and 13C NMR, FT-IR, and MS spectra, and their antimicrobial activity against gram positive and gram negative bacteria and antifungal activity were evaluated. The thienyl-substituted derivative showed significant activity against Bacillus licheniformis. Bacillus subtilis, Staphylococcus aureus, Klebsiella pneumonia (bacteria), and Fusarium solani (fungi). The activities of the fluoro-substituted substituted derivative against some bacterial strains and of the thienyl-substituted derivative against fungi were found to be similar to those of standard drugs.
Synthesis, spectral characterization, DNA interaction, antioxidant, and antimicrobial studies of new water soluble metal(II) complexes of morpholine based ligand
Abstract
A new series of metal(II) complexes 1–5 of the type [M(L)(AcO)2H2O], where L is a bidentate ligand, 2-(3-morpholinopropylimino)methylphenol and M is Mn(II) (1), Co(II) (2), Ni(II) (3), Cu(II) (4), and Zn(II) (5), have been isolated and characterized by physico-chemical and spectral methods. Spectroscopic data supported the square pyramidal geometry around the central metal ion in the complexes 1–5. Absorption spectra and viscometric data indicated that the complexes 1–5 interacted with calf thymus (CT) DNA via intercalative strategy. Cleavage activities of complexes 1–5 with CT DNA were analyzed by gelelectrophoretic method. The in vitro antioxidant activity of complexes 1–5 was tested using the DPPH assay. The complexes 1–5 have been tested for antimicrobial activity against some pathogenic bacterial and fungal species by the agar well diffusion method.
Ultrasound-accelerated synthesis of quinoline-based luminescent imines exhibiting large Stokes shift
Abstract
High yield synthesis of quinoline-based fluorescent imines, exhibiting the highest Stokes shift exceeding 380 nm (>18 000 cm–1), is reported in the current publication. Such large difference in the excitation and emission wavelengths is quite unusual. Synthesis of imines was accelerated by ultrasound. Both experimental and theoretical studies have been performed.
Synthesis, biological evaluation, and molecular docking studies of diacylhydrazine derivatives possessing 1,4-benzodioxan moiety as potential anticancer agents
Abstract
A series of diacylhydrazine derivatives containing 1,4-benzodioxan 1-17 has been designed, synthesized and evaluated for antitumor activity. Most of the synthesized compounds demonstrated potent antitumor activity and low toxicity. Compound 10 demonstrated the most potent biological activity against MCF-7 cancer cell line, which was comparable with the positive control 5-fluorouracil. Docking simulation by positioning compound 10 into the MetAP2 structure active site was performed to explore the possible binding model.
Synthesis of biologically active nickelocenyl–amino acid conjugates using 1,3-dipolar cycloaddition click reactions
Abstract
Herein we present the study of synthesis of novel bio-organometallic conjugates using 1,3-dipolar cycloaddition click reactions. Amino acid azides such as 4-azido-D-homoalanine, 5-azido-D-ornithine and 6-azido-D-lysine were reacted with ethynyl nickelocene to synthesize nickelocenyl-homoalanine conjugate (1), nickelocenyl-ornithine conjugate (2), and nickelocenyl–lysine conjugate (3) using Cu(I) compounds as catalysts. This synthetic strategy resulted in high yields (68–76%) of nickelocene-amino acid conjugates. Structure characterization of these purified bio-organometallic conjugates was performed using FT-IR, 1H, and 13C NMR spectroscopy. Antibacterial and antifungal activities of these products were tested against Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Streptococcus pneumonia, Alternaria alternate, Aspergillus flavus, and Aspergillus niger using the disc diffusion method. Rifampicin (antibacterial) and fluconazole (antifungal) were used as standard drugs. Results of antimicrobial activities were found to be promising.
New ferrocenyl guanidines as potent antioxidants, protein kinase inhibitors and cytotoxic agents against human leukemia THP-1 cell line
Abstract
Six new ferrocenyl guanidines were synthesized and characterized by elemental analysis, FT-IR and 1H and 13C NMR. Compounds 1–6 were screened for antioxidant, protein kinase inhibition, lethality of brine shrimp, and cytotoxicity against the human leukemia THP-1 cell line. The compounds demonstrated moderate to significant activities. Antioxidant activity of the synthesized compounds was evaluated by DPPH % inhibition with IC50 values. All compounds 1–6 showed notable antioxidant activity with DPPH having IC50 values between 23.2–15.1 and noteworthy brine shrimp lethality. Compound 6 demonstrated the highest cytotoxicity against brine shrimps with LC50 of 9.09 μg/mL. Protein kinase inhibition activity showed significant hyphea formation inhibition at 100 μg/disc with 10 to 13 mm clear zone of inhibition for the compounds 2–6. The compounds were screened for in vitro cytotoxicity using human leukemia cell line (THP-1 ATCC#TIB-202). Among all compounds, the most significant activity was demonstrated by compounds 6 and 5 with IC50 of 3.88 and 5.59 μg/mL which was comparable with the standard 5-flourouracil and vincristine drugs.
Biological evaluations and spectroscopic characterizations of 3-(4-ethoxyphenyl)-2-methylacrylate based organotin(IV) carboxylates derivatives
Abstract
Six new organotin(IV) carboxylates, [Me2SnL2] (1), [n-Bu2SnL2] (2), [n-Oct2SnL2] (3), [Me3SnL] (4), [n-Bu3SnL] (5) and [Ph3SnL] (6), where L = 3-(4-ethoxyphenyl)-2-methylacrylate, have been synthesized and characterized by FT-IR, NMR spectroscopy and elemental analyses. The synthesized compounds were tested for in vitro antibacterial and antifungal activities. The complexes 4–6 demonstrated higher activity than the complexes 1–3. UV-Vis absorption spectroscopy indicated that the ligand and its complexes interacted with DNA via partial intercalation as well as minor groove binding.
Synthesis and characterization of novel chalcones linked 3-[1-(3-chlorophenyl)-3-(pyren-1-yl)]-1H-pyrazole moiety
Abstract
New series of pyrenyl–pyrazole based chalcones have been synthesized and characterized via the condensation of 1-(3-chlorophenyl)-3-(pyren-1-yl)-1H-pyrazole-4-carbaldehyde with different substituted acetophenones in alkaline media. Structures of the newly synthesized compounds were elucidated from spectroscopic and elemental analysis data.
Simple and efficient method for aromatization of tetrahydro-β-carbolines by using K2S2O8 as a catalyst and its antimicrobial activity comparison with molecular docking studies
Abstract
A novel and efficient aromatization of tetrahydro-β-carbolines under mild conditions using K2S2O8 as a catalyst was developed. The method is applicable for all kinds of C1 substituted systems. All synthesized compounds were screened for their in vitro antibacterial activity against Staphylococus aureus, Bacillus subtilis, Escherichia coli, and Klebsiella pneumonia, as well as fungi, such as Aspergillus flavus and Fusarium oxysporum. Compounds 4b, 4g, 4i, and 4k demonstrated excellent in vitro antibacterial and antifungal activities than the standard drugs. The docking studies were carried out for most active compounds 4b, 4g, 4i, and 4k.
The new green procedure for pyrazolopyrimidinone based dihydropyrimidinones and their antibacterial screening
Abstract
A series of novel hybrid aza heterocycles containing pyrazolopyrimidinone and dihydropyrimidinone scaffolds was developed using Cu(II) catalyzed Biginelli condensation as an efficient, new green synthetic method under mild and solvent free conditions. Pyrazolopyrimidinone based aldehydes, alkyl acetoacetates and urea/thiourea were used as the components in the reaction to afford hybrid aza heterocycles in high to excellent yields. The products were screened for in vitro antibacterial activity and all of those demonstrated high to excellent activity.
New complexes of 4-[(4-fluorophenyl)amino]-4-oxobut-2-enoic acid with selected transition metal ions: Synthesis, thermal, and magnetic properties
Abstract
Complexes of 4-[(4-fluorophenyl)amino]-4-oxobut-2-enoic acid, HL, with Mn(II), Co(II), Ni(II), Cu(II), Nd(III), Gd(III), and Er(III) were synthesized and characterized by various physico-chemical methods: elemental analysis, FT-IR, TG, DTG, DSC, TG/FT-IR, XRF, XRD, and magnetic measurements using the Gouy’s method and a SQUID-VSM magnetometer. The complexes were found to be hydrates (except Er(III) complex) containing 1 to 4 molecules of water. The carboxylate groups acted as bidentate ligands.
Letters to the Editor
Effect of protonation on the photocatalytic activity of the layered titanate Rb2Nd2Ti3O10
Abstract
It was found that the contact of the layered oxide Rb2Nd2Ti3O10 with an aqueous solution gives rise to a protonation process, which leads to lowering the oxide photocatalytic activity in reactions of hydrogen evolution from a water-alcohol solution.
One-pot electrochemical synthesis of acid anhydrides from alcohols
Abstract
One-pot indirect electrochemical oxidation of alcohols in the methylene chloride–aqueous solution of sodium hydrocarbonate two-phase system in the presence of potassium iodide, 4-acetylamino-2,2,6,6-tetramethylpiperidin-1-oxyl, and 2,6-lutidine results in the formation of the corresponding acid anhydrides with yield up to 80%. The reaction occurs at room temperature and is complete after passing 6 F/mol of electricity.
Reaction of N-tert-butyl-2-haloaldimines with thiolcarboxylic acids
Abstract
The reactions of N-tert-butyl-2-chloroaldimine with thiolcarboxylic acids occurs along two pathways: nucleophilic substitution of chlorine in the primary iminium salt by acylmercapto group and reduction of the C–Cl bond in the iminium cation. The reactions of thiolcarboxylic acids reaction with 2-bromoaldimine take exclusively the second pathway, specifically reduction of the C–Br bond in the cation of the primary iminium salt. Acylmercapro-substituted iminium salts and aldehydes and their acetals are synthesized.
1-Methyl-2-oxopyrrolidinium perchlorate ionic liquid in synthesis of 5-ethoxycarbonyl-3,4-dihydropyrimidin-2(1H)-ones
Abstract
A multicomponent Biginelli reaction in a solvent-free conditions catalyzed by 1-methyl-2-oxopyrrolidinium perchlorate ionic liquid was studied. The сondensation of aromatic aldehydes, urea (thiourea), and acetoacetic ester yielded substituted 5-ethoxycarbonyl-3,4-dihydropyrimidin-2(1H)-ones(thiones) in 75–97% yield.
Synthesis of precursors to new tripodal phosphine oxide ligands
Abstract
A number of precursors of new tripodal ligands was obtained by hydroxyethylation of the starting tris(2-hydroxyphenyl)phosphine oxide, followed by conversion of the resulting tris[2-(2-hydroxyethoxy) phenyl]phosphine oxide to trimesylate. The treatment of the latter with LiBr or NaN3 afforded the corresponding tribromo and triazido derivatives.
Solubility of salts of d-elements in organic and water-organic solvents: V. Inner-sphere chalcogen S–S contacts in the [Ni(DMSO)4(H2O)2]Cl2 solvate
Abstract
It was proved by the IR spectroscopy that the first coordination sphere of nickel cations in the NiCl2·2DMSO·9H2O, NiCl2·5DMSO·4H2O, and NiCl2·4DMSO·2H2O compounds contains dimethyl sulfoxide and water ligands. According to X-ray structural analysis, in crystals of the NiCl2·4DMSO·2H2O compound, noncovalent contacts between sulfur atoms of neighboring dimethyl sulfoxide molecules are realized in the inner sphere of the complex.
Simulation of metal ion coordination sphere in crystals with fluorite structure
Abstract
Using quantum-chemical methods, it has been found that the structure of fluorite coincides with the symmetry and coordination number of central calcium atom in the (Oh)-Ca7F14 cluster. The Ca–F and F–F interatomic distances in the cluster are 3–4% shorter than in the crystal. The symmetry of the (Oh)–(ScCa6F14)+ cluster mimicking the cationic defect after the β-decay of 45Ca does not correspond to the energy minimum. The increase in the cation charge from 1.79 to 2.80 a. u. reduces the radius of the first coordination sphere by 0.14 Å. For ytterbium dihalides, the bond lengths Yb–F 2.344, Yb–Cl 2.897 Å and the cation charges 1.81, 1.64 a. u., respectively, have been found.
Nafion- and aquivion-based nanocomposites containing detonation nanodiamonds
Abstract
Nafion- and Aquivion-based composite solid polyelectrolytes containing deagglomerated detonation nanodiamonds were studied by the impedance spectroscopy method. It was found that introduction of these dopants leads to a substantial increase in proton conductivity of hybrid membranes with low relative humidity.