On the Reaction of 3-Acetyl Coumarin with Alkyl Phosphites. Structural Confirmations Based on X-Ray Crystallography

3-Acetyl coumarin ( 1 ) reacts with dialkyl phosphites at 100°;C for 8 h to give the phosphonates 2 . Under the same experimental conditions, 1 reacts with trialkyl phosphites to form a mixture of the phosphonates 2 and 3 . The molecular structures of these products were elucidated by x-ray crystallography.     

Solid phase synthesis of two muramyl pentapeptide derivatives

Solid phase peptide synthesis (SPPS) of two selected muramyl pentapeptide derivatives is described. The simplicity of removing the protecting groups via one-step deprotection and cleavage from the resin is the biggest advantage of SPPS. Using this method, two muramyl pentapeptide derivatives, D-MurN₃-L-Ala-D-iGlu-L-Lys-D-Ala-D-Ser (5) and D-MurN₃-L-Ala-D-iGlu-L-Lys-D-Ala-D-Ala (6), were obtained. Their chemical structures were confirmed by high-resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR) spectroscopy. To determine the absolute configuration of the carbon atom in the side chain of the muramic acid derivative, single-crystal X-ray diffraction measurements were recorded.     

Synthesis,Characterization and Photoluminescence of Lanthanide Metal‐organic Frameworks,Constructed from Triangular 4,4′,4″‐s‐triazine‐1,3,5‐triyl‐p‐aminobenzoate Ligands

Eight isomorphous metal‐organic frameworks: [Ln₂(TATAB)₂(H₂O)(DMA)₆]·5H₂O (Ln = Sm ( 1 ), Eu ( 2 ), Gd ( 3 ), Tb ( 4 ), Dy ( 5 ), Er ( 6 ), Tm ( 7 ), Yb ( 8 )); TATAB = 4,4′,4″‐s‐triazine‐1,3,5‐triyl‐p‐aminobenzoate, DMA = N,N‐dimethylacetamide), were synthesized by the self‐assembly of lanthanide ions, TATAB, DMA and H₂O. Single‐crystal X‐ray crystallography reveals they are three dimensional frameworks with 2‐fold interpenetration. Solid‐state photoluminescence studies indicate ligand‐to‐metal energy transfer is more efficient for compounds 2 and 4 which exhibit intense characteristic lanthanide emissions at room temperature.     

New osmium cluster compounds containing the heterocyclic ligand 2,3-bis-(diphenylphosphino)quinoxaline (dppq): Ligand isomerization and crystal structures of dppq, the isomeric clusters Os3(CO)10(dppq), and HOs3(CO)9[μ-2,3-PhP(η-C6H4)(Ph2P)quinoxaline]

Treatment of the labile cluster 1,2-Os₃(CO)₁₀(MeCN)₂ (1) with the diphosphine ligand 2,3-bis(diphenylphosphino)quinoxaline (dppq) at room temperature affords 1,2-Os₃(CO)₁₀(dppq) (2b) as the kinetic product of ligand substitution in 84% yield. 2b isomerizes to the thermodynamically more stable dppq-chelated cluster 1,1-Os₃(CO)₁₀(dppq) (2c) as the sole observable product under CO at temperatures below 358 K. The kinetics for the conversion of 2b → 2c have been investigated by NMR spectroscopy in CDCl₃ over the temperature range 323-353 K, and the reaction was found to exhibit a rate law that is first order in 2b. The calculated activation parameters [ΔH^≠ = 25.4(4) kcal/mol; ΔS^≠ = −3(1) eu] support an intramolecular isomerization scenario, one that involves the migration of phosphine and CO groups about the cluster polyhedron. The disposition of the dppq ligand in the isomeric Os₃(CO)₁₀(dppq) clusters has been established by X-ray crystallography and ³¹P NMR spectroscopy. Photolysis of 2c at 366 nm leads to CO loss and ortho metalation of one of the aryl groups on the Ph₂P moiety to furnish the hydride cluster HOs₃(CO)₉[μ-PhP(η¹-C₆H₄)(Ph₂P)quinoxaline] (3). The isomerization behavior exhibited by 2b follows that of related diphosphine-substituted Os₃ clusters prepared by us.     

Alternative syntheses and X-ray diffraction analyses of the parent tricarbaborane compounds [nido-7,8,9-C3B8H11], [nido-7,8,10-C3B8H11] and [1-(η-C5H5)-closo-1,2,4,10-FeC3B8H11]

Reaction of the neutral tricarbaborane nido-7,8,9-C₃B₈H₁₂ (1) with triethylamine in CH₂Cl₂ led to quantitative deprotonation and isolation of the corresponding Et₃NH⁺ salt of the [nido-7,8,9-C₃B₈H₁₁]⁻ anion (2). This was converted into PSH⁺ and Me₄N⁺ salts via metathetic cation exchange. Heating of the solid Me₄N⁺[7,8,9-C₃B₈H₁₁]⁻ in mineral oil at 350 °C for 2 h resulted in thermal rearrangement and isolation of the cage isomeric compound Me₄N⁺[7,8,10-C₃B₈H₁₁]⁻. Finally, compound 1 was directly complexed via reaction with [CpFe(CO)₂]₂ (Cp = η⁵-C₅H₅) to generate the ferratricarbollide sandwich [1-Cp-closo-1,2,4,10-FeC₃B₈H₁₁] (4) in 60% yield. The structures of all the generic compounds of tricarbollide chemistry, 1 (PSH⁺ salt), 2 (MePPh₃⁺salt), and 4, were established unambiguously by an X-ray diffraction analysis.     

Crystallographic Analysis of FCC ? BCT Martensitic Transformation in the Alloy Fe-22% Ni-0.8% C

The infinitesimal deformation (ID) approach is applied to analyse the crystallography involved in the fcc to bct martensitic transformation for the case of (101)_γ[<formula><overline>1</overline>01</formula>]_γ twinning shear as LIS (lattice invariant shear) system in the alloy Fe-22% Ni-0.8% C. Analytical solutions are derived for habit plane orientation, orientation relationships between austenite and martensite phases, and the magnitude of the total shape deformation, etc. In order to compare numerical solutions with the ID approach and phenomenological crystallographic theory, the corresponding crystallographic parameters are calculated by using the Ledbetter and Dunn (L-D) theory. The numeric values obtained are compared with the predictions of the phenomenological crystallographic theories, and with experimental results.     

Wax deposition rate model for heat and mass coupling of piped waxy crude oil based on non-equilibrium thermodynamics

In this paper, wax deposition in waxy crude oil transportation process was regarded as an irreversible process. Based on the entropy production rate equations, the linear phenomenological equations for the diffusion of wax molecules were derived by using the theory and method of non-equilibrium thermodynamics and heat-mass transfer. Combined with the mass and energy conservation laws, the differential equations of heat and mass transfer in the process of pipeline transportation were established, and the molecular diffusion rate of dissolved wax was solved. On the basis of this, the mathematical model of actual wax deposition rate was established by considering the attachment process and scouring process of the wax molecules. Taking an oil pipeline in Daqing as an example, the change law and influencing factors of the wax molecular diffusion coefficient, the wax deposition rate, and the net wax deposition rate were studied by numerical simulation. The wax deposition rate test results of the laboratory loop test were compared with the theoretical calculation results in order to analyze the accuracy and the adaptability of heat and mass coupling mechanism and to provide a theoretical basis for further study of wax deposition in the process of waxy oil pipeline transportation.