Effect of different immobilization strategies on chiral recognition properties of Cinchona‐based anion exchangers

In the enantiomeric separation of highly polar compounds, a traditionally challenging task for high‐performance liquid chromatography, ion‐exchange chiral stationary phases have found the main field of application. In this contribution, we present a series of novel anion‐exchange‐type chiral stationary phases for enantiomer separation of protected amino phosphonates and N‐protected amino acids. Two of the prepared selectors possessed a double and triple bond within a single molecule. Thus, they were immobilized onto silica support employing either a thiol‐ene (radical) or an azide‐yne (copper(I)‐catalyzed) click reaction. We evaluated the selectivity and the effect of immobilization proceeding either by the double bond of the Cinchona alkaloid or a triple bond of the carbamoyl moiety on the chromatographic performance of the chiral stationary phases using analytes with protecting groups of different size, flexibility, and π‐acidity. The previously observed preference toward protecting groups possessing π‐acidic units, which is a typical feature of Cinchona‐based chiral stationary phases, was preserved. In addition, increasing the bulkiness of the selectors’ carbamoyl units leads to significantly reduced retention times, while very high selectivity toward the tested analytes is retained.     

Aqueous Synthesis of Methylammonium Lead Halide Perovskite Nanocrystals

Methylammonium lead halide perovskite nanocrystals offer attractive optoelectronic properties but suffer from fast degradation in the presence of water. In contradiction to this observation, we demonstrate the possibility of a direct aqueous synthesis of CH₃NH₃PbX₃ (X=Br or Cl/Br) nanocrystals through the reaction between the lead halide complex and methylamine when the pH is maintained in the range of 0–5. Under these synthetic conditions, the positively charged surface of the perovskite nanocrystals and the proper ionic balance help to prevent their decomposition in water. Additional surface capping with organic amine ligands further improves the photoluminescence quantum yield of the perovskite nanocrystals to values close to 40 %, ensures their stability under ambient conditions for several months, and their photoluminescence performance under continuous 0.1 W mm^?2 405 nm light irradiation for over 250 hours.     

The Pr1-xLaxMgNi4-yCoy alloys: Synthesis,structure and hydrogenation properties

The influence of substitution Pr for La and Ni for Co on hydrogen storage properties of Pr_1-xLa_xMgNi_4-yCo_y (х = 0; 0.5, у = 0–3) alloys were studied. The existences of solid solutions have been found. It is shown that the synthesized alloys absorb hydrogen at room temperature and hydrogen pressure 0.1–10 bar. For some of the studied compounds, the formation of hydrides with cubic and orthorhombic structures was found. Hydrogen capacity for Pr_1-xLa_xMgNi_4-yCo_y alloys increases with Co content increasing and reaches 6.6 H/f.u. for PrMgNi₂Co₂. For electrochemical hydrogenation different trend was observed. With increasing of Co content discharge capacity slightly increases only to y = 0.5, and after y > 0.5, decreases. Highest discharge capacity is equal to 305 mА∙h/g for Pr_0.5La_0.5MgNi_3.5Co_0.5, and 268 mА∙h/g for PrMgNi_3.5Co_0.5 at current densities 50 mА/g and 200 mA/g, respectively. Influence of Co and number of activation cycles on HRD value of PrMgNi_4-yCo_y alloys was investigated. Additionally, obtained results of the electrochemical properties were compared with related compounds.     

MOF Scaffold for a High‐Performance Mixed‐Matrix Membrane

A novel composite membrane consisting of an interconnected MOF scaffold coated with cross‐linked poly(ethylene glycol) (PEG) has been developed. As a result of its unique structure, the membrane shows an exceptional 18‐fold permeability enhancement as compared to pristine PEG membranes, without compromising the selectivity. This performance is unattainable with current mixed‐matrix membranes (MMMs). Our optimized membrane has a permeability of 2700 Barrer with a CO₂/N₂ selectivity of 35, which surpasses the latest Robeson upper bound.     

Comparative studies of immobilized chiral stationary phases based on polysaccharide derivatives for enantiomeric separation of 15 azole compounds

Immobilized polysaccharide‐based columns showed excellent enantioselectivity in normal phase separation mode. In this work, enantioseparation abilities of four immobilized polysaccharide‐derived chiral stationary phases (Chiralpak IA, Chiralpak IB, Chiralpak IC, and Chiralpak ID) toward 15 azole compounds were evaluated. Separation was carried out using n‐hexane as mobile phase with ethanol, 1‐propanol, 1‐butanol, and 2‐propanol as modifiers. And twelve compounds have achieved baseline separation with the resolutions ranging between 2.05 and 21.73. The enantioseparation on the four polysaccharide‐based chiral columns using different alcohol modifiers was compared. In general, the best separation performance was identified as Chiralpak IC, which was able to resolve 11 compounds to baseline and two partially under the screening conditions. Separation on Chiralpak IB was not satisfactory, because only four compounds were baseline separated.     

Bimetallic Nanoparticles in Supported Ionic Liquid Phases as Multifunctional Catalysts for the Selective Hydrodeoxygenation of Aromatic Substrates

Bimetallic iron–ruthenium nanoparticles embedded in an acidic supported ionic liquid phase (FeRu@SILP+IL‐SO₃H) act as multifunctional catalysts for the selective hydrodeoxygenation of carbonyl groups in aromatic substrates. The catalyst material is assembled systematically from molecular components to combine the acid and metal sites that allow hydrogenolysis of the C=O bonds without hydrogenation of the aromatic ring. The resulting materials possess high activity and stability for the catalytic hydrodeoxygenation of C=O groups to CH₂ units in a variety of substituted aromatic ketones and, hence, provide an effective and benign alternative to traditional Clemmensen and Wolff–Kishner reductions, which require stoichiometric reagents. The molecular design of the FeRu@SILP+IL‐SO₃H materials opens a general approach to multifunctional catalytic systems (MM′@SILP+IL‐func).     

Effect of the surfactant alkyl chain length on the stabilisation of lyotropic nematic phases

Lyotropic quaternary mixtures of potassium alkanoates (KCx) and sodium alkyl sulphates (NaCxS), where x is the number of carbon atoms in their alkyl chains, were prepared to investigate the effect of the surfactant alkyl chain length on the stabilisation of lyotropic nematic phases. The lyotropic mixtures investigated were formed by the dissolution of KCx (NaCxS) surfactants in the mixture of Rb₂SO₄/1-decanol/water (Na₂SO₄/1-decanol/water), separately. The uniaxial-to-biaxial nematic phase transitions were identified from the temperature dependence of the birefringences of the nematic phases by means of laser conoscopy. The micelle dimensions were obtained from small-angle X-ray scattering measurements. It was observed that the increase in the surfactant alkyl chain length causes the micellar growth in the plane perpendicular to the main amphiphile bilayer. The surfactant alkyl chain length plays a key role on the shape anisotropy of micelles, which triggers the orientational fluctuations that are responsible for the stabilisation of the different lyotropic nematic phases.     

Combined Fluorescence and NMR Studies of Reversed HPLC Stationary Phases with Different Ligand Chain Lengths

Alkyl chain bonded reversed HPLC phases consisting of 6 to 30 carbon atoms are investigated by fluorescence spectroscopy, steady-state and time-resolved fluorescence anisotropy, and solid-state NMR spectroscopy. The structure and dynamics of the interphase formed by alkyl chains and liquid phase penetrating each other are studied as a function of alkyl chain length. Increasing alkyl chain lengths lead to enhanced partitioning of the fluorescent probe diphenylhexatriene (DPH) into the interphase, as monitored by fluorescence decay curves. The concomitant spectral red shift of DPH fluorescence excitation maxima is evidence of increased interphase polarizability. Time-resolved fluorescence anisotropy measurements reveal that the motion of the probe molecule in the interphase is wobble in cone-like. Cone angles and rotational correlation times _R change from = 63° and _R = 0.75 ns in C₆ phases to = 42° and _R = 1.50 ns in C₃₀ phases, thus indicating decreasing probe mobility with increasing ligand length. This interpretation is supported by ¹³C CP/MAS NMR spectra, which show reduced contributions of alkyl chain gauche conformations, i.e., enhanced interphase order, in phases with long alkyl chains and high surface coverage. A concomitant increase in the line-widths of ¹H MAS NMR peaks indicates reduced mobility of the longer chains. The spectroscopic observations are consistent with the results of HPLC separations, where enhanced shape selectivity is found with increasing ligand length, rod-shaped molecules like DPH showing the greatest increase in retention time.     

New subvalent bismuth telluroiodides incorporating Bi<Subscript>2</Subscript> layers: the crystal and electronic structure of Bi<Subscript>2</Subscript>TeI

Two new subvalent bismuth telluroiodides, Bi₂TeI and Bi₄TeI_1.25, were prepared by the gas-phase synthesis. The compositions of these phases were determined by energy-dispersive X-ray spectroscopy. X-ray diffraction study of melt grown Bi₂TeI single crystals demonstrated that the compound crystallizes in the monoclinic system (space group C/2m) with the unit cell parameters a = 7.586(1) Å, b = 4.380(1) Å, c = 17.741(3) Å, β = 98.20°. The layered crystal structure of Bi₂TeI consists of weakly bonded two dimensional blocks with a stoichiometry of the title compound. The blocks are stacked along the c axis. Each block consists of eight atomic layers alternating in the Te-Bi-I-Bi-Bi-I-Bi-Te order and includes a double layer of bismuth atoms. Based on the results of ab initio quantum-chemical calculations, the title compound is expected to possess a pronounced anisotropy of conductivity.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 86–91, January, 2005.     

应用于蛋白质、多肽、氨基酸快速分离的不同孔径硅胶聚合物键合相

使用７μｍ的单分散不同孔径的硅胶为基体，表面键合唱 共聚有机物层，并在此类键合相上考察了蛋白质，多肽，氨基酸分离的色谱性能，实验结果表明，梯度冲洗下可得有蛋白酶，核糖核酸酶，溶菌酶、糜蛋白醇原，卵清蛋白的快速而良好的分离；在３ｍｉｎ内获得两种结构相似氨基酸的基线分离。