Repeated Elements of the Structure of Liquid Monoethanolamine

For the first time, in F-structures of liquid monoethanolamine that were constructed by molecular dynamics simulations at various temperatures, repetition of structural triangles formed by hydrogen-bonded coordinating atoms (O and N) was revealed. A correlation was found between the revealed features of the molecular dynamics structures and the characteristics of monoethanolamine clusters determined by quantum mechanical calculations. It was shown that there are two main types of triangular motifs that ensure strong binding in the system owing to peculiarities of the electron distribution.     

CO2 Aggregation on Monoethanolamine: Observations from Rotational Spectroscopy

The initial stages of the gas-phase nucleation between CO₂ and monoethanolamine were investigated via broadband rotational spectroscopy with the aid of extensive theoretical structure sampling. Sub-nanometer-scale aggregation patterns of monoethanolamine-(CO₂)_n, n=1–4, were identified. An interesting competition between the monoethanolamine intramolecular hydrogen bond and the intermolecular interactions between monoethanolamine and CO₂ upon cluster growth was discovered, revealing an intriguing CO₂ binding priority to the hydroxyl group over the amine group. These findings are in sharp contrast to the general results for aqueous solutions. In the quinary complex, a cap-like CO₂ tetramer was observed cooperatively surrounding the monoethanolamine. As the cluster approaches the critical size of new particle formation, the contribution of CO₂ self-assembly to the overall stability increases.     

幻数团簇丝氨酸八聚体:结构和手性特征

自从2001年丝氨酸八聚体第一次在质谱中被观察到,这种奇特的幻数团簇就受到研究者们的广泛关注。丝氨酸八聚体具有显著的同手性优势,而且它的手性能够通过对映选择性取代反应传递给其他分子。一些研究者提出这种丝氨酸八聚体的同手性优势很可能与生命的同手性起源相关。本文综述了丝氨酸八聚体的产生、结构和手性特征等方面的研究结果和进展,其中包括运用串联质谱（MS/MS）,气相H/D交换,离子淌度,红外解离光谱等多种实验方法以及理论计算对丝氨酸八聚体及含有取代单元的八聚体的相关研究。这些结果逐步地揭示了丝氨酸八聚体的结构特点和性质,进一步加深了人们对其在手性识别和手性传递方面的作用的理解。然而,由于体系的复杂性,真正地理解其结构、同手性选择性的原因以及其在生物分子同手性起源中的作用仍是一个非常具有挑战性的问题。     

Effect of Composition and Structure of Aqueous Monoethanolamine Solutions on Carbon Dioxide Sorption and Desorption in Purification of Gas Mixtures

Possibility of raising the efficiency of the monoethanolamine purification of gas mixtures to remove carbon dioxide is demonstrated with consideration for the real intermolecular interactions and the structuring in the absorbent solution. The composition and structure of individual aqueous monoethanolamine solutions with various concentrations and of the same solutions saturated with carbon dioxide were examined. The methods of viscometry and conductometry demonstrated that, at monoethanolamine concentrations exceeding 12 ± 2 wt %, micelles are formed on the background of the existence of associates with intermolecular hydrogen bonds. This necessitates use of high temperatures (120?140°C) in the stage of carbon dioxide desorption. It was found that using a 12 wt % aqueous solution of monoethanolamine in purification of gas mixtures makes it possible to lower the desorption temperature of carbon dioxide to 90°C. This process is more efficient than the standard technology of CO₂ removal from a 30 wt % monoethanolamine solution. This is so because, in addition to a lower expenditure of heat, the extraction of carbon dioxide grows by 16% at a simultaneous decrease in the absorbent expenditure by at least a factor of 2.5.     

Biological N Removal from Wastes Generated from Amine-Based CO2 Capture: Case Monoethanolamine

Large-scale amine-based CO₂ capture will generate waste containing large amounts of ammonia, in addition to contaminants such as the actual amine as well as degradation products thereof. Monoethanolamine (MEA) has been a dominant amine applied so far in this context. This study reveals how biological N removal can be achieved even in systems heavily contaminated by MEA in post- as well as pre-denitrification treatment systems, elucidating the rate-limiting factors of nitrification as well as aerobic and denitrifying biodegradation of MEA. The hydrolysis of MEA to ammonia readily occurred both in post- and pre-denitrification treatment systems with a hydraulic retention time of 7 h. MEA removal was ≥99?±?1 % and total nitrogen removal 77?±?10 % in both treatment systems. This study clearly demonstrates the advantage of pre-denitrification over post-denitrification for achieving biological nitrogen removal from MEA-contaminated effluents. Besides the removal of MEA, the removal efficiency of total nitrogen as well as organic matter was high without additional carbon source supplied.     

ChemInform Abstract: Structure and Reactivity of Binary Au12Pt Cluster.

An all‐electron scalar relativistic calculation on the geometrical structure and reactivity of Au₁₂Pt cluster is performed by DFT with the generalized gradient approximation at PW91 level.     

B20N20团簇的结构与稳定性

B3LYP/6-31G* density functional theory calculations have been carried out on the structure and stability of ten B20N20 clusters. It was found that two new proposed isomers with two octagons, twelve hexagons, eight squares in Cab and C2 symmetry were more stable than the isomer with sixteen hexagons and six squares in C2 symmetry which was previously deemed to the most stable by 79.5 and 13.8 kJ/mol respectively. The isomer with two decagons in S10 symmetry is much higher in energy than the most stable structure in C4h symmetry by 637.2 kJ/mol.     

具有类蜻蜓状双核铜-联吡啶水簇配合物

本文介绍了一种合成[Cu2(bipy)2(H2P2O7)(OH)2]?7H2O双核铜水簇配合物的简单方法,晶体结构解析证明7个结晶水相互之间形成丰富的二维水簇聚合物[(H2O)7]n,水簇再与主体结构中的羟基OH集团形成强的氢键作用,整个配合物结构从仿生学角度考虑类似蜻蜓状。通过对这种水簇聚合物的研究,有助于改善无法解释的含结晶水的某些配合物性质的模型,更好地理解水分子在化学和生物过程中的结构和行为。     

Two-Step Electrodialysis Treatment of Monoethanolamine to Remove Heat Stable Salts

Electrodialysis technology was adapted to removal of heat stable salts from aqueous solutions of alkanolamine absorbents, with monoethanolamine as example. Removal of anions of heat stable salts by electrodialysis from a 30 wt % aqueous solution of monoethanolamine with the degree of carbonation of 0.2 mol of CO₂ per mole of monoethanolamine was studied. The two-step removal of heat stable salts by electrodialysis allows the monoethanolamine loss to be reduced and the concentration of residual CO₂ in the absorbent solution to be decreased. The suggested two-step electrodialysis treatment scheme allows the concentration of heat stable salts to be maintained on the required level from the viewpoint of their corrosion activity, the total volume of the concentrate to be decreased by 50%, and the monoethanolamine loss to be decreased by 30%. The treatment unit with the circulation volume of the monoethanol absorbent of 100 m³ h^–1 was calculated for confirming the efficiency of the two-step electrodialysis treatment scheme. As compared to the one-step electrodialysis treatment scheme, the two-step scheme ensures recovery of 50% of monoethanolamine at the same efficiency of the removal of heat stable salts.     

A Hexanuclear Cobalt Cluster with Tetracubane-like Topology: Synthesis,Structure and Magnetic Properties

One hexanuclear cobalt cluster [Co_2~ ⅢCo_4 ~Ⅱ(L)_4(CH_3 COO)_2(MeO)_4]·MeOH(1) was synthesized by the reaction of H_2L(H_2L=2-((2-hydroxy-4-methoxy-benzylideneamino)methyl)phenol) and Co(OAc)_2·4 H_2O in MeOH under solvothermal conditions. Complex 1 crystalizes in the triclinic space group ■ with a = 14.397(3), b = 16.625(3), c = 18.992(4) ?, α = 109.47(3)°, β = 99.24(3)°, γ = 112.37(3)°, Dc = 1.464 g/cm3, Z = 2, V = 3741.7(2) ?3, the final R = 0.0781 and w R = 0.1436 for 13051 observed reflections with I 2σ(I). In the structure of 1, two cobalt ions are in 3+ oxidation states and four cobalt ions are in 2+ valence states. The six cobalt atoms are held together by six phenolate oxygen atoms from four L2– ligands, four oxygen atoms from two chelating acetates and four μ3-O atoms from four Me O– groups. The six cobalt atoms are located at six corners of four defective cubanes. Thus, complex 1 displays tetracubane-like topology. Solid-state dc magnetic susceptibilities were measured for 1 in the 2.0～300 K range. Antiferromagnetic interactions were determined for 1.     

Cluster Structure of the Surface of Plasticized Cellulose Triacetate Films

The influence of plasticizers, dibutyl phthalate and triphenyl phosphate, on the structure of the surface of cellulose triacetate films was studied. The parameters of an infinite cluster of the cellulose triacetate molecules on the film surface, the correlation radius ξ of the spatial distribution of density, the degree ρ_s of surface filling of the cluster, and the fractal dimensionality D, were calculated from the electron-microscopic data, using the cluster model.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 2, 2005, pp. 306–309.Original Russian Text Copyright © 2005 by Novikov, Varlamov, Mnatsakanov.     

一种新颖酰基硫脲金属簇合物的合成与晶体结构

报道了一种新型酰基硫脲金属簇合物[Cu₆(HL)₆] (HL＝N-乙氧羰基-N'-4-氟苯基硫脲)的合成和晶体结构. 对化合物用元素分析、红外光谱、核磁共振谱、差热-热重分析确定了配合物的组成, 并经X射线单晶衍射法确定了其单晶结构. 晶体结构表明, 该化合物属于三斜晶系, 空间群, a＝1.2508(11) nm, b＝1.3011(11) nm, c＝1.4686(12) nm, a＝102.401(14)°, β＝97.859(2)°, γ＝114.700(13)°, V＝2.051(3) nm³, Z＝1, D_c＝1.687 Mg/m³. 标题化合物是由六个铜离子和六个硫脲配体组成的笼状金属簇合物, 每一个硫脲配体上与乙氧酰基相连的氮原子与铜进行配位, 并且配体上硫羰基上的硫原子与铜也发生配位作用, 使它们互相连接形成畸变的多面体结构.     

Synthesis and Crystal Structure of Novel Fe_3 Cluster Compound

ＳｙｎｔｈｅｓｉｓａｎｄＣｒｙｓｔａｌＳｔｒｕｃｔｕｒｅｏｆＮｏｖｅｌＦｅ_３ＣｌｕｓｔｅｒＣｏｍｐｏｕｎｄ￥ＬｕＱｉｎｇ－Ｗｅｉ；ＷａｎｇＹｉ－Ｂｉｎｇ；ＷｕＢａｏ－Ｓｈａｎ；ＳｕｏＱｕａｎ－Ｌｉｎｇ；ＬｉｕＳｈｕ－Ｔａｎｇ；ＨｕＸｉａｎｇ；（Ｄｅ?..     

Ligand-Induced Tuning of the Electronic Structure of Rhombus Tetraboron Cluster

A neutral boron carbonyl complex B₄(CO)₃ is generated in the gas phase and is characterized by infrared plus vacuum ultraviolet (IR+VUV) two-color ionization spectroscopy and quantum chemical calculations. The complex is identified to have a planar C_2v structure with three CO ligands terminally coordinated to a rhombus B₄ core. It has a closed-shell singlet ground state that correlates to an excited state of B₄. Bonding analyses on B₄(CO)₃ as well as the previously reported B₄ and B₄(CO)₂ indicate that the electronic structure of rhombus tetraboron cluster changes from a close-shell singlet to an open-shell singlet in B₄(CO)₂ and to a close-shell singlet in B₄(CO)₃, demonstrating that the electronic structures of boron clusters can be effectively tuned via sequential CO ligand coordination.     

B2Be2簇的结构与成键性质的研究

用HF／6-31Gabinitio法对B2Be2簇9种异构体27个电子态的结构进行了全构型优化,再用大基组二次组态相互作用QCISD（T）／6-311G方法进行单点计算，9种异构体的稳定性顺序是：h＞i＞g＞e＞f＞c＞a＞d＞b.通过结构转变中的Walsh图、能量间隙、键数参数（BNP）和键电荷的研究，揭示了B2Be2的成键特征.     

Cations Insertion in Molybdenum Cluster Compounds: Electronic Structure and Electrochemical Study Using Cavity Microelectrode

Owing to the high lability of cations in the three-dimensional framework of K_1+x Mo₁₂S₁₄ (0 ≤ x ≤ 1.6), first-principles calculations and electrochemical methods have been carried out to study the insertion of cations in the empty channels of this compound. The cavity microelectrode that is a suitable electrode for powder material analysis has been used in voltammetric experiments. Results obtained for Li⁺, Na⁺, Rb⁺, K⁺, Cs⁺ and NH₄ ⁺ cations are presented and discussed.