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61.
62.
《Acta Crystallographica. Section C, Structural Chemistry》2018,74(5):608-617
The two single‐enantiomer phosphoric triamides N‐(2,6‐difluorobenzoyl)‐N′,N′′‐bis[(S)‐(−)‐α‐methylbenzyl]phosphoric triamide, [2,6‐F2‐C6H3C(O)NH][(S)‐(−)‐(C6H5)CH(CH3)NH]2P(O), denoted L‐1 , and N‐(2,6‐difluorobenzoyl)‐N′,N′′‐bis[(R)‐(+)‐α‐methylbenzyl]phosphoric triamide, [2,6‐F2‐C6H3C(O)NH][(R)‐(+)‐(C6H5)CH(CH3)NH]2P(O), denoted D‐1 , both C23H24F2N3O2P, have been investigated. In their structures, chiral one‐dimensional hydrogen‐bonded architectures are formed along [100], mediated by relatively strong N—H…O(P) and N—H…O(C) hydrogen bonds. Both assemblies include the noncentrosymmetric graph‐set motifs R22(10), R21(6) and C22(8), and the compounds crystallize in the chiral space group P1. Due to the data collection of L‐1 at 120 K and of D‐1 at 95 K, the unit‐cell dimensions and volume show a slight difference; the contraction in the volume of D‐1 with respect to that in L‐1 is about 0.3%. The asymmetric units of both structures consist of two independent phosphoric triamide molecules, with the main difference being seen in one of the torsion angles in the OPNHCH(CH3)(C6H5) part. The Hirshfeld surface maps of these levo and dextro isomers are very similar; however, they are near mirror images of each other. For both structures, the full fingerprint plot of each symmetry‐independent molecule shows an almost asymmetric shape as a result of its different environment in the crystal packing. It is notable that NMR spectroscopy could distinguish between compounds L‐1 and D‐1 that have different relative stereocentres; however, the differences in chemical shifts between them were found to be about 0.02 to 0.001 ppm under calibrated temperature conditions. In each molecule, the two chiral parts are also different in NMR media, in which chemical shifts and P–H and P–C couplings have been studied. 相似文献
63.
S. V. Partsevskaya T. B. Zheltonozhskaya D. O. Klymchuk 《Molecular Crystals and Liquid Crystals》2018,671(1):128-139
AbstractA series of amphiphilic MOPEO-b-PCL copolymers (DBCs), based on biocompatible methoxypoly(ethylene oxide) with Mn=4.5?kDa and poly(ε-caprolactone) of a variable chain length, was synthesized by an anionic ring-opening block copolymerization. The structural investigations, performed by DSC and WAXS methods, revealed the microphase separation in DBC bulk structure and the existence of separate amorphous regions and microcrystalline domains of MOPEO and PCL blocks. Spectrophotometry and SLS were used to study the self-assembling of DBC macromolecules in selective dioxane/aqueous solution and to determine the main micellization parameters (CMC and -ΔG°). The DBC micelles morphology and their specific aggregation in mixed solvent were shown. 相似文献
64.
Two new complexes of [Mn(2-MPyzCI)2Cl2].H2O (1) and [Mn(2-MPyzCI)2(H2O)2](NO3)2 (2) were synthesized from the reaction of MnX2.4H2O (X=Cl? and NO3?) with 2-cyanopyrazine in methanolic solution. The chelating methyl pyrazine-2-carboximidate (2-MPyzCI) ligand is formed via the methanolysis of 2-cyanopyrazine. Although coordination environment around manganes(II) ions is similar, but these complexes are different in geometrical position of 2-MPyzCI ligands. As both compounds are synthesized under the same reaction conditions, the only difference between these two complexes are counter ions and changing of geometrical position of ligands can be considered as a result of influence of the counter-anions on the molecular structures. 相似文献
65.
Yong-Jin Zhao Jian-Ping Ma Jianzhong Fan Yan Geng Yu-Bin Dong 《Acta Crystallographica. Section C, Structural Chemistry》2020,76(6):605-615
The tridentate organic ligand 4,4′,4′′‐(4,4,8,8,12,12‐hexamethyl‐8,12‐dihydro‐4H‐benzo[9,1]quinolizino[3,4,5,6,7‐defg]acridine‐2,6,10‐triyl)tribenzoic acid ( H3L ) has been synthesized (as the methanol 1.25‐solvate, C48H39NO6·1.25CH3OH). As a donor–acceptor motif molecule, H3L possess strong intramolecular charge transfer (ICT) fluorescence. Through hydrogen bonds, H3L molecules construct a two‐dimensional (2D) network, which pack together into three‐dimensional (3D) networks with an ABC stacking pattern in the crystalline state. Based on H3L and M(NO3)2 salts (M = Cd and Zn) under solvothermal conditions, two metal–organic frameworks (MOFs), namely, catena‐poly[[triaquacadmium(II)]‐μ‐10‐(4‐carboxyphenyl)‐4,4′‐(4,4,8,8,12,12‐hexamethyl‐8,12‐dihydro‐4H‐benzo[9,1]quinolizino[3,4,5,6,7‐defg]acridine‐2,6‐diyl)dibenzoato], [Cd(C48H37NO6)(H2O)3]n, I , and poly[[μ3‐4,4′,4′′‐(4,4,8,8,12,12‐hexamethyl‐8,12‐dihydro‐4H‐benzo[9,1]quinolizino[3,4,5,6,7‐defg]acridine‐2,6,10‐triyl)tribenzoato](μ3‐hydroxido)zinc(II)], [Zn2(C48H36NO6)(OH)]n, II , were synthesized. Single‐crystal analysis revealed that both MOFs adopt a 3D structure. In I , partly deprotonated HL 2? behaves as a bidentate ligand to link a CdII ion to form a one‐dimensional chain. In the solid state of I , the existence of weak interactions, such as O—H…O hydrogen bonds and π–π interactions, plays an essential role in aligning 2D nets and 3D networks with AB packing patterns for I . The deprotonated ligand L 3? in II is utilized as a tridentate building block to bind ZnII ions to construct 3D networks, where unusual Zn4O14 clusters act as connection nodes. As a donor–acceptor molecule, H3L exhibits fluorescence with a photoluminescence quantum yield (PLQY) of 70% in the solid state. In comparison, the PL of both MOFs is red‐shifted with even higher PLQYs of 79 and 85% for I and II , respectively. 相似文献
66.
Kalina Mambourg Laurie Bodart Nikolay Tumanov Steve Lanners Johan Wouters 《Acta Crystallographica. Section C, Structural Chemistry》2020,76(3):205-211
The condensation reaction of 2‐mercapto‐3‐methoxybenzaldehyde with 3‐aminopyridine afforded an unexpected N‐alkylated [1,5]dithiocine instead of the N‐salicylideneaniline. The proposed mechanism for this condensation involves a strong intramolecular hydrogen bond between the thiol and the amine groups, leading to a second condensation. The corresponding product, i.e. 4,10‐dimethoxy‐13‐(pyridin‐3‐yl)‐6H,12H‐6,12‐epiminodibenzo[b,f][1,5]dithiocine methanol 0.463‐solvate, C21H18N2O2S2·0.463CH3OH, was characterized by single‐crystal X‐ray diffraction analysis. The supramolecular structure shows π–π stacking and S…S interactions in the crystal packing. Within the asymmetric unit, two geometries of the N atom are observed. Although a planar geometry should be expected, a pyramidal one is observed due to the crystal packing. The presence of the two geometries was further supported by density functional theory (DFT) calculations that show an electronic energy difference of less than 2 kJ mol?1 between the two conformers. 相似文献
67.
68.
ABSTRACTA new opposed type double-stage large volume cell has been developed to compress large volume samples to more than 100?GPa (Mbar) pressure. A pair of second-stage diamond anvils is introduced into the first-stage Paris–Edinburgh press. The double-stage large volume cell allows the generation of ultrahigh pressures using a large culet diameter of the second-stage diamond anvils (diameters of 0.5–1.2?mm). Pressure generation up to 131?GPa has been achieved by using the culet diameter of 0.5?mm. Sample volume of the double-stage large volume cell can be more than ~100 times larger than that of conventional Mbar experiment using a diamond anvil cell. The double-stage large volume cell has a large opening in the horizontal plane for X-ray measurements, which is particularly suited for the multi-angle energy dispersive X-ray diffraction measurement, thus opening a new way of in situ structural determinations of amorphous materials at Mbar pressures. 相似文献
69.
Transformation of flow turbulence structure with cavitation occurrence, determination of the flow conditions favorable for nucleation of cavitation bubbles, influence of the statistical structure of turbulence on this process and the inverse effect of cavitation on the flow dynamics are challenging problems in modern fluid mechanics. The paper reports on the results of statistical processing of the velocity fields measured by a PIV technique in cavitating flow over a 2D symmetric hydrofoil for four flow conditions, starting from a cavitation-free regime and finishing by unsteady cloud cavitation. We analyze basic information on the statistical structure of velocity fluctuations in the form of histograms and Q-Q diagrams along with profiles of the mean velocity and turbulent kinetic energy. The research reveals that the flow turbulence pattern and distributions of turbulent fluctuations change significantly with the cavitation development. Under unsteady cloud cavitation conditions, the probability density function of the fluctuating velocity has a two-mode distribution, which indicates switching of two alternating flow conditions in a region above the hydrofoil aft part due to periodic passing of cavitation clouds. Behaviors of the mean and most probable velocities unexpectedly appear to be different with a monotonous increase of the incoming flow velocity. This finding must be caused by modification of the skewness coefficient of the fluctuating velocity. 相似文献
70.
Stabilised mixed velocity–pressure formulations are one of the widely-used finite element schemes for computing the numerical solutions of laminar incompressible Navier–Stokes. In these formulations, the Newton–Raphson scheme is employed to solve the nonlinearity in the convection term. One fundamental issue with this approach is the computational cost incurred in the Newton–Raphson iterations at every load/time step. In this paper, we present an iteration-free mixed finite element formulation for incompressible Navier–Stokes that preserves second-order temporal accuracy of the generalised-alpha and related schemes for both velocity and pressure fields. First, we demonstrate the second-order temporal accuracy using numerical convergence studies for an example with a manufactured solution. Later, we assess the accuracy and the computational benefits of the proposed scheme by studying the benchmark example of flow past a fixed circular cylinder. Towards showcasing the applicability of the proposed technique in a wider context, the inf–sup stable P2–P1 pair for the formulation without stabilisation is also considered. Finally, the resulting benefits of using the proposed scheme for fluid–structure interaction problems are illustrated using two benchmark examples in fluid-flexible structure interaction. 相似文献