Experimental and ab initio calculational studies on nitrato[2,4-dichloro-6-((pyridin-2-ylmethylimino)methyl)phenolato]copper(II)

The mononuclear Schiff-base copper(II) compound, [Cu(C₁₃H₉C_l2N₂O)(NO₃)], has been synthesized and characterized by elemental analysis and X-ray single crystal determination. The compound crystallizes in the orthorhombic, space group Cmc2₁ with unit cell dimensions a?=?6.713(1), b?=?22.147(3), c?=?9.976(1)?Å?, M _r?=?405.67, V?=?1483.2(3)?ų, Z?=?4, R ₁?=?0.0568 and wR ₂?=?0.1331. X-ray structure determination revealed that the compound possesses crystallographic mirror symmetry. The Cu^II ion in the compound is five-coordinate in a distorted trigonal bipyramid with one O and two N atoms of the Schiff-base and by two O atoms of the nitrate anion. In the crystal structure, the molecules are linked via intermoleclular C?H?···?O non-classical hydrogen bonds, forming a two-dimensional network. Density functional theory (DFT) and Hartree-Fock (HF) calculations of the structure, atomic charge distribution and natural bond orbital analyses have been performed. The calculated results show that the Cu^II ion mainly adopts spd² hybridization and forms five bonds with the NNO donor set of the Schiff-base ligand and with two O atoms of nitrate from four orientations. The coordinate stabilization energies show that the Schiff-base copper(II) compound is very stable.     

Miniature open channel scrubbers for gas collection

An open channel scrubber is proposed as a miniature fieldable gas collector. The device is 100 mm in length, 26 mm in width and 22 mm in thickness. The channel bottom is rendered hydrophilic and liquid flows as a thin layer on the bottom. Air sample flows atop the appropriately chosen flowing liquid film and analyte molecules are absorbed into the liquid. There is no membrane at the air-liquid interface: they contact directly each other. Analyte species collected over a 10 min interval are determined by fluorometric flow analysis or ion chromatography. A calculation algorithm was developed to estimate the collection efficiency a priori; experimental and simulated results agreed well. The characteristics of the open channel scrubber are discussed in this paper from both theoretical and experimental points of view. In addition to superior collection efficiencies at relatively high sample air flow rates, this geometry is particularly attractive that there is no change in collection performance due to membrane fouling. We demonstrate field use for analysis of ambient SO₂ near an active volcano. This is basic investigation of membraneless miniature scrubber and is expected to lead development of an excellent micro-gas analysis system integrated with a detector for continuous measurements.     

A theoretical investigation into chiral phosphoric acid-catalyzed asymmetric Friedel-Crafts reactions of nitroolefins and 4,7-dihydroindoles: reactivity and enantioselectivity

This article mainly focused on high level Density Functional Theory (DFT) studies on the chiral phosphoric acid-catalyzed Friedel-Crafts reactions between 4,7-dihydroindoles and nitroolefins. Firstly, the reactivities of 4,7-dihydroindole and indole in the chiral phosphoric acid-catalyzed Friedel-Crafts reactions with nitroolefin have been compared. The higher reactivity of 4,7-dihydroindole could be attributed to its higher HOMO energy as well as its more suitable trajectory to attack the nitroolefin in the transition state. Secondly, the origin of the enantioselectivity of the chiral phosphoric acid-catalyzed Friedel-Crafts reaction of 4,7-dihydroindole with nitroolefin has been studied using complete models on PBE1PBE/[6-311+G(d,p), 6-31G(d,p)] level. When (S)-1b was used as the catalyst, the enantioselectivity of the reaction is entirely controlled by the steric effect between the catalyst and the substrate. Whereas for catalyst (S)-1c the enantioselectivity is determined by the solvent effect.     

四种新型柔性吡啶基配合物的合成、结构及配体构象与配合物结构的关系

合成了柔性配体3-吡啶甲酸-1,2-乙二酯(3-pyridinecarboxylic acid 1,2-ethanediyl ester,pcaede),并将其分别与Co盐和Hg盐进行组装,得到4个新配合物[Co(pcaede)2Cl2.2CH3CN.H2O]n(1),[Co(pcae-de)2Cl2.H2O]n(2),[Hg(pcaede)I2]n(3)和[Hg(pcaede)Br2]n(4),对其进行了元素分析、红外光谱及X射线单晶结构分析.配合物1和2为含有孔道的一维链状结构,配合物3是1D内消旋螺旋链,配合物4则是锯齿形1D链状结构.研究结果显示,孔道中填充的溶剂分子和平衡阴离子对配合物的组装有显著的影响.此外对4个配合物中配体的构象进行了理论计算.     

The weak nuclear force, the chirality of atoms, and the origin of optically active molecules

Although chemical phenomena are primarily associated with electrons in atoms, ions, and molecules, the masses, charges, spins, and other properties of the nuclei in these species contribute significantly as well. Isotopes, for instance, have proven invaluable in chemistry, in particular the elucidation of reaction mechanisms. Elements with unstable nuclei, for example carbon-14 undergoing beta decay, have enriched chemistry and many other scientific disciplines. The nuclei of all elements have a much more subtle and largely unknown effect on chemical phenomena. All nuclei are innately chiral and, because electrons can penetrate nuclei, all atoms and molecules are likewise chiral. This article describes in considerable detail the discovery of chiral nuclei, how this unusual chirality may influence the chemical behavior of atoms and molecules, and how atomic chirality may have been responsible for the synthesis of optically active molecules in the pre-biotic world.     

Theoretical study of the potential-energy surface of C2NP

 The B3LYP/6-311G(d) and CCSD(T)/6-311G(2df) (single-point) methods have been used to investigate the singlet potential energy surface of C₂NP, in which seven stationary isomers and seventeen interconversion transition states are involved. At the final CCSD(T)/6-311G(2df)//B3LYP6-311G(d) level with zero-point vibrational energy correction the lowest-lying isomer is a linear NCCP followed by two linear CNCP isomers at 23.9  and CCNP at 65.8 kcal mol⁻¹, respectively. The three isomers are kinetically very stable towards both isomerization and dissociation, and CCNP is even more kinetically stable than CNCP – by 14.3 kcal mol⁻¹ despite its high energy. Further comparative calculations were performed at the QCISD and QCISD(T) levels with the 6-311G(d) and 6-311G(2d) basis sets to obtain more reliable structures and spectroscopy for the three isomers. The calculated bond lengths, rotational constant, and dipole moment for NCCP were in close agreement with the experimentally determined values. Finally, similarities and discrepancies between the potential energy surface of C₂NP and those of the analogous species C₂N₂ and C₂P₂ were compared. The results presented in this paper might be helpful for future identification of the two still unknown yet kinetically very stable isomers CNCP and CCNP, both in the laboratory and in interstellar space. Received: 3 January 2001 / Accepted: 6 June 2001 / Published online: 30 October 2001     

海藻酸钙凝胶微球粒径的理论计算与实验

通过静电液滴发生器制备海藻酸钙凝胶微球,通过理论推导得到了微球粒径的计算公式.理论计算的结果表明,凝胶微球粒径的大小取决于静电压、电极距离、针头内径大小、注射器流速、海藻酸钠粘度和表面张力以及凝胶化体积收缩系数.理论计算结果与实验结果吻合得相当好.     

Theoretical Study of Rg·NO (Rg=He,Ne, Ar and Kr) Complexes

Rg·NO (Rg=He, Ne, Ar and Kr) complexes were studied using ab initio calculations. The neutral Rg·NO complex geometry and vibrational frequencies were calculated with the cc-pVDZ basis set at the CCSD(T) level of theory. The calculations show that the geometry of the Rg·NO complexes is a skewed T-shape with the Rg atom on the oxygen side of the NO molecule, and that the RgNO bond angle increases with mass. The dissociation energies (DE) and ionization energies (IE) of the neutral Rg·NO complexes, and the dissociation energies of Rg·NO+ ionic complexes were calculated using Gaussian-2 (G2) methods and a high accuracy energy model. The ionization energies of the neutral Rg·NO complexes range from 9.265 eV for He·NO to 9.132 eV for Kr·NO and the dissociation energies of Rg·NO+ range from 0.017 eV for He·NO+ to 0.156 eV for Kr·NO+, in line with the expectation based on the increasing polarizability of the Rg atom.     

表面电化学和电化学催化研究进展——97'国际电化学联合大会和97'国际表面电化学会议综述

表面电化学和电化学催化研究进展①——９７＇国际电化学联合大会和９７＇国际表面电化学会议综述孙世刚（厦门大学化学系,固体表面物理化学国家重点实验室厦门３６１００５）表面电化学和电化学催化是当前极为活跃的研究领域．这首先得益于近年来各种物理和光谱技术的飞...     

超价化合物

超价分子和离子是一类奇特而迷人的物种,它们的出现对经典的Ｌｅｗｉｓ－Ｌａｎｇｍｕｉｒ主族元素价层成键理论提出了挑战。本文从超价化合物的发展史、定义、理论描述、表示方法、合成、稳定性、周期性变化、光谱表征等方面对超价化合物进行了较详细的论述。