The following bromobismuthates of organic cations (dipyridinoalkane derivatives) are synthesized and characterized: (4-NH2PyC5)BiBr5 (I), (2-MePyC2)BiBr5 (II), (2-NH2PyC10)BiBr5 center dot 0.65H(2)O (III), (2-NH2PyC10)(4)H5O2(BiBr6)(3) (IV), (2-NH2PyD6)(2)KBi2Br11 (V), (2-NH2PyC6)H3OBiBr6 center dot 2.33H(2)O (VI), and (2-NH2PyC6)(3)(BiBr6)(2) center dot CH3CN (VII). Three compounds obtained (I-III) contain the zigzag 1D chain (BiBr5) (n) . A new type of 1D chains, (KBi2Br11) (n) , is found in the structure of compound V. Pseudo-1D chains of BiBr6 (3-) anions can be observed in the 3D structures of compounds IV, VI, and VII. The crystallographic data were deposited with the Cambridge Crystallographic Data Centre (CIF files CCDC 1569478 (I)-1569484 (VII), respectively)
The title compounds, C9H12O6 and C10H14O6, were formed by careful hydrolysis of the corresponding diethyl esters. Their single crystals were grown from an ethyl acetate/hexane mixture. Crystals of both compounds have monoclinic (P21) symmetry with a single molecule in the asymmetric unit. Both crystal structures are very similar and display four –CO—OH O C(OH)– hydrogen bonds, forming a two-dimensional double-layered framework.
New β‐diazopyrrole and β‐triazenylpyrrole derivatives were synthesized from isoxazoles and pyridinium salts in two and three steps, respectively. The apoptotic/necrotic difference for these compounds was estimated on THP‐1 cell line. The most effective of the panel is methyl 3‐diazo‐2‐(2,4‐dimethylphenyl)‐4‐phenyl‐3H‐pyrrole‐5‐carboxylate which demonstrated cytotoxic activity from the lowest concentration of 3.3 μM with a steep rise of the apoptotic effect and the largest apoptotic/necrotic difference within the range of 3.3 to 33 μM. Moreover, this diazopyrrole showed the highest sum total of apoptotic and necrotic AUCs within the same low range of concentrations. Methyl 2‐(4‐bromophenyl)‐3‐diazo‐4‐(3‐methoxyphenyl)‐3H‐pyrrole‐5‐carboxylate and methyl 5‐(4‐bromophenyl)‐3‐(3‐methoxyphenyl)‐4‐(piperidin‐1‐yl/morpholin‐4‐yldiazenyl)‐1H‐pyrrole‐2‐carboxylates were found to be quite promising compounds which deserve further cytophysiological and mechanistic research using different cell lines.
It is known that both cis,fac-[RuCl2(DMSO)(3)(H2O)] (1a) and trans,cis,cis-[RuCl2(DMSO)(2)(H2O)(2)] (2a) complexes, which are formed on the dissolution of trans and cis-isomers of [RuCl2(DMSO)(4)] in water, demonstrate light-induced anticancer activity. The first stage of 1a photochemistry is its transformation to 2a occurring with a rather high quantum yield, 0.64 +/- 0.17. The mechanism of the 1a 2a phototransformation was studied by means of nanosecond laser flash photolysis and ultrafast pump-probe spectroscopy. The reaction occurs in the picosecond time range via the formation and decay of two successive intermediates interpreted as Ru(ii) complexes with different sets of ligands. A tentative mechanism of phototransformation is proposed.
A new organic inorganic hybrid material (C15H14N4)BiBr5 center dot H2O with an optical band gap of 2.24 eV, having 1-D chains of bromobismuthate anions in its composition, has been obtained from an aqueous solution and characterized. The partial replacement of Br by I resulted in the formation of a thermally stable (<155 degrees C) black compound (C15H14N4)BiBrI4 center dot H2O with an optical band gap of 1.70 eV, which can be proposed as a promising light-harvesting material for dye-sensitized solid-state solar cells. Further replacement of Br by I results in the formation of red-orange colored (C15H14N4)BiI5 with a band gap of 2.10 eV.
This paper addresses hybrid ion exchange membranes fabricated by the synthesis of amorphous zirconium phosphate (dopant contents from 0.5 to 24 wt%) directly in the pore and channel system of heterogeneous cation-exchange membrane RALEX® CM (by in situ technique). The incorporation of zirconium phosphate nanoparticles into the membrane system of pores and channels leads to the displacement of the pore water. As a result, the cation transport numbers increase. The hybrid materials thus obtained are characterized by increased ionic resistance and enhanced monovalent ion selectivity. The former effect was eliminated by fabrication of a surface-modified membrane. The relative simplicity of modification, together with the benefits of the hybrid materials make them promising for some membrane processes. Using 31P MAS NMR and elemental analysis, considerable difference between the zirconium phosphate composition inside and outside the membrane was found.
The effect of an interplay between electrostatic and excluded volume interactions on the conformational behavior of a dipolar chain has been studied theoretically and by means of molecular dynamics simulations. Every monomer unit of the dipolar chain comprises a dipole formed by a charged group of the chain and an oppositely charged counterion. The counterion is assumed to freelymove around the chain but keeping the distance between oppositely charged ions (the dipole length) fixed. The novelty of the developed mean-field theory is that variations of the dipole parameters (the dipole length and the counterion size) have been accounted for in both electrostatic and excluded volume contributions to the total free energy of the dipolar chain. It has been shown that conformational transitions between swollen and collapsed states of the chain can be induced by fine-tuning the balance between electrostatic and excluded volume interactions. In particular, in lowpolar media not only globule but also extended coil conformations can be realized even under strong electrostatic attraction. The results ofMD simulations of a dipolar chain with variable dipolar length support theoretical conclusions.
A new class of anthracene complexes with a metal coordinated at the central ring was applied in catalysis for the first time. As a result, a simple and efficient protocol for reductive amination that involves CO as a reducing agent has been developed. The rhodium complex [(cyclooctadiene)Rh(C10H4Me2(OMe)4)]+ (1 mol%) catalyses such reactions under mild conditions (40–130 °C) and produces a variety of amines in good yields (74–95%) without affecting the functional groups. The protocol is acceptable for all combinations of aldehydes (aromatic and aliphatic), ketones (aromatic and aliphatic) and amines (aromatic and aliphatic; primary and secondary).
We developed a ruthenium-catalyzed reductive ester synthesis from aldehydes or ketones and carboxylic acids using carbon monoxide as a deoxygenative agent. Multiple factors influencing the outcome of the reaction were investigated. Best results were obtained for commercially available and inexpensive benzene ruthenium chloride; as low as 0.5 mol % of the catalyst is sufficient for efficient reaction. Competitive studies demonstrated that the presence of even 1000 equiv of alcohol in the reaction mixture does not lead to the corresponding ester, which clearly indicates that the process is not a simple reductive esterification but a novel type of Ru-catalyzed redox process.
A new organic-inorganic hybrid material composed of O-D bromobismuthate anions and bis(4-cyano-1-pyridino)pentane cations was synthesized and characterized. The replacement of Br with I resulted in a decrease in the optical band gap from 2.88 eV for (C17H18N4)(2)Bi2Br10 to 1.59 eV for (C17H18N4)BiI5. Thus, (C17H18N4)BiI5 can be proposed as a candidate material for solid state solar cells.
Three hybrid 1,1'-(1,n-alkanediyl)bis(4-methylpyridinium) iodobismuthates 1 - 3 were prepared by a facile solution route and showed thermal stability in air up to 230°C. The structures of solid 1 and 3 contain zero-dimensional anions, and the structure of 2 contains one-dimensional linear anionic chains [BiI5]n2n-. Photoluminescence (PL) in the spectral range between 600 and 750 nm was observed for 1 and 2. DFT calculations and optical studies confirmed that compounds 1−3 are semiconductors with band gaps of 1.73−2.10 eV, which corresponds with their intense black (for 2) or red (for 1 and 3) colors. The optical absorption of 2 in the red spectral range is primarily due to charge transfer from the I5p orbitals at the top of the valence band to the Bi6p orbitals at the bottom of the conduction band.
Carbon monoxide as an example of reducing agent, in contrast to classical reducing agents (hydrogen and metal hydrides), can provide very high atom precision for reductive addition of substrates with various functional groups. This enables synthesis of new compounds with unique structures and properties.
Transition metal oxides are attractive noble metal-free catalysts of the oxygen reduction for application at the cathode of alkaline membrane fuel cells or metal-air batteries. However, despite of a rapidly increasing number of publications devoted to the oxygen electrocatalysis on transition metal oxides, a clear picture regarding the relations between their structure and composition on the one hand and electrocatalytic activity on the other hand is lacking. This short review discusses challenges facing researchers seeking to understand electrocatalysis of the oxygen reduction reaction on transition metal oxides.
Investigation of charge delocalization (redistribution) in a SpnF-catalyzed reaction that proceeds through overlapping Diels–Alder and bis-pericyclic mechanisms has shown that it is better represented as a nonpolar cycloaddition rather than a cationic rearrangement.
In situ XRD and NMR experiments combined with molecular dynamics simulations using the grand canonical ensemble (GCMD) show that cation size, charge and solvation energy play critical roles in determining the interlayer expansion of smectite clay minerals when exposed to dry supercritical CO2 under conditions relevant to the earthâ€™s upper crust, petroleum reservoirs, and geological CO2 sequestration conditions (323 K and 90 bar). The GCMD results show that the smectite mineral, hectorite, containing interlayer alkali and alkaline earth cations with relatively small ionic radii and high solvation and hydration energies (e.g., Li+, Na+ Mg2+, and Ca2+) does not intercalate dry CO2 and that the fully collapsed interlayer structure is the energetically most stable configuration. With increasing cation size and decreasing cation solvation energy, the energy barrier to CO2 intercalation decreases. With K+, Rb+, Cs+, Sr2+, and Ba2+ the monolayer structure is the stable configuration, and CO2 should spontaneously enter the interlayer. With Cs+ there is not even an energy barrier for CO2 intercalation, in agreement with the experimental XRD and NMR results that show clay layer expansion and CO2 incorporation. The number of intercalated CO2 molecules decreases with increasing size of the alkali cation but does not vary with ion size for the alkaline earth cations. 13C NMR spectroscopy and the GCMD simulations show that the average orientation of the intercalated CO2 molecules is with their O-C-O axes parallel to the basal clay surface and that they undergo a combination of rapid rotation about an axis perpendicular to the main molecular axis and wobbling motion with respect to the basal surface. Incorporation of CO2 in the interlayer decreases the coordination of Cs+ by the oxygen atoms of the basal surfaces, which is compensated by CO2 molecules entering their solvation shell, as predicted based on previously published NMR results. The GCMD simulations show that the strength of the interaction between the exchangeable cation and the clay structure dominates the intercalation energetics in dry scCO2. With relatively small cations, the cation-clay interactions outcompete cation solvation by CO2 molecules. The computed residence times for coordination among of interlayer species are consistent with the computed energetics.
The Nafion-117 membranes in the Li+ form with pore-intercalated aprotonic organic solvents were prepared. The prepared materials were characterized by IR, impedance, and 7Li NMR spectroscopy. The solvent uptake of the membranes is shown to be controlled by the composition of organic solvents and their mixtures as well as by the conditions of the preliminary treatment of the initial membranes. For the Nafion-117 membrane, the degree of solvation can be improved by the preliminary treatment with alcohols, especially by the thermal treatment in methanol. Conductivity of the membranes is shown to increase with increasing content of the sorbed solvents. The best conductivity at 25 °C (2.5 × 10−3 and 1.6 × 10−3 S cm−1) was attained for the electrolytes based on the Nafion-117 membrane in lithium form with sorbed ethylene carbonate-propylene carbonate and ethylene carbonate-dimethoxyethane mixtures, respectively.
In, Nb, Mo-doped lithium complex phosphates and HZr2(PO4)3 with NASICON-type structure were synthesized in this paper. Particle size distribution lies between 50 and 300 nm. The obtained samples were characterized by X-ray diffraction analysis, scanning electron microscopy and X-ray microanalysis. Investigation of the catalytic properties of synthesized compounds in the C1C2 alcohols conversions showed that heterovalent doping has a determining effect on the obtained catalysts' activity and selectivity.
It is shown that the thermodynamic factors and the dopant ability to change the degree of oxidation and acid function of the catalysts play a key role in methanol and ethanol conversion. A number of catalysts show the high activity and selectivity of the formation of dimethyl and diethyl ethers and ethylene. High selectivity for C4 hydrocarbons is achieved by LiZr2(PO4)3 and Li0.5Zr2P2.5Mo0.5O12 catalysts (64 and 49%, respectively) in the case of ethanol conversion.
Hydrothermal crystallization pathways of amorphous ceric phosphate gels were found to be determined by the ammonia concentration in a reaction medium. This allows for highly selective hydrothermal synthesis of various finely crystalline ceric phosphates, including Ce(PO4)(HPO4)0.5(H2O)0.5, (NH4)2Ce(PO4)2(H2O), and previously unknown NH4Ce2(PO4)3. The structure of the latter compound was solved from powder X-ray diffraction data. It appeared to be isostructural to ammonium thorium phosphate, NH4Th2(PO4)3; in this crystal structure, large channels (5.07 Å~ 3.79 .) located along the c-axis are occupied by NH4+ ions.
Recently, we have investigated the three-dimensional structures of CPT in complexes with the ground-state substrate analogs carrying hydrophobic and positively charged side chains: benzylsuccinic acid (BZS) and S-(2-guanidinoethylmercapto)succinic acid (GEMSA). That allowed us to identify Leu211 and Leu254 – earlier unknown determinants of substrate recognition by CPT as density of their interaction with substrates and localization of their side chains in the S1′-subsite were dependent on substrate’s structure. The role of Leu211 and Leu254 as structure determinants of hydrophobic selectivity of CPT was confirmed by site-directed mutagenesis. In the present work, we compare the structural organization of the CPT active site in complexes with transition state analogs of phenylalanine and arginine-containing substrates to evaluate structural basis of the enzyme’s catalytic activity to a broad range of substrates.
Rh-catalyzed one-step reductive amidation of aldehydes has been developed. The protocol does not require an external hydrogen source and employs carbon monoxide as a deoxygenative agent. The direction of the reaction can be altered simply by changing the solvent: reaction in THF leads to amides, whereas methanol favors formation of tertiary amines.