吡哆胺对1,4-二羰基化合物清除机理的密度泛函理论研究

吡哆胺（PM）能够清除生物体新陈代谢过程中产生的活性二羰基化合物,此类化合物能与体内的氨基酸作用生成有毒的吡咯类化合物。本文用密度泛函理论B3LYP方法在6-31G*基组水平上,研究了PM与OPA反应的机理。计算结果表明,该反应可通过两个连续的步骤完成。首先,通过竞争反应生成一个四氢吡咯类化合物;随后,该化合物经过平行反应脱水生成最终产物。理论上,反应过程中还有可能生成亚胺类化合物,但计算结果表明其为副反应。最后,本文讨论了空间位阻效应对反应性质的影响。所有计算结果与实验结果非常吻和。     

Synthesis, Crystal Structure and Electrochemical Properties of the Complex Cd（α-FRA）2（Phen）（H2O）

1 INTRODUCTION The syntheses and structures of carboxyl complex- es have captured the interest of chemists for years due to their potential applications in many fields, such as materials, medicine, molecular electro-che- mistry and biochemistry[1～3]. So far, to the best of our knowledge, cadmium complexes with aromatic carboxylic acid as ligands have been intensively studied[4～7], but those with heterocyclic carboxylic acid as ligands are much less. α-Furoic acid is widely used in orga…     

Catena-dichloro(4,4′-dimethyl-2,2′-bipyridine)Cadmium(Ⅱ),a New One-dimensional Chain with Blue Fluorescent Emission

A new μ-chloro-bridged one-dimensional coordination polymer Cd(dmbpy)Cl2n(dmbpy=4,4′-dimethyl-2,2′-bipyridine) has been synthesized and structurally characterized by elemental analyses=IR=UV spectra and single-crystal X-ray diffraction.The complex crystallizes in the monoclinic system=space group C2/c with a=17.745(4)=b=10.326(2)=c=7.3382(15)=β=106.85(3)o=V=1286.9(4)3=Z=4=C12H12N2Cl2Cd=Mr=367.54=Dc=1.897 g/cm3=F(000)=720=λ(MoKα)=0.71073=μ=2.089 mm-1=R=0.0368 and wR=0.1048 for 1041 observed reflections(I > 2σ(I)).Cadmium(II) adopts a distorted octahedral coordination geometry and adjacent coordination chains are intercalated in a zipper-like fashion into 2D layers through the π-π stacking interactions between dmbpy.Fluorescent     

Synthesis and Crystal Structure of a Dinuclear Cu(II) Complex with Tridentate Schiff Base and Azido Bridge

1 INTRODUCTION The azido ligand is an efficient superexchange path-way for propagating magnetic interaction between theparamagnetic centers, such as copper(II), giving di-nuclear, tetranuclear, 1D, 2D and 3D complexes[1～4].The versatility of this ligand due to its diverse bin-ding modes leads to the variation in magnetic pro-perties that depend on its orientation with respect tothe magnetic centers. In general, the bridging modesobserved for the azido group are endtoend and en-don. In…     

Theoretical Study of La , Ca modified and Pure PbTiO_3 Nanocrystals

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Adsorption and Vibration of O on the Pt Stepped Surfaces

1 INTRODUCTION Atom adsorption on transition metal surfaces has attracted special attention as a basis for understand- ing the fundamental processes of oxidative cataly- sis. An oxygen-covered platinum surface for example, plays a central role in several important reactions, such as oxidation of carbon monoxide[1]. Moreover, the behavior of oxygen in the proximity of surface defects like kinks and steps is a central issue in understanding the chemisorption processes on ca- talytic surfaces…     

Na+, Mg2+, and Zn2+ binding to all tautomers of adenine, cytosine, and thymine and the eight most stable keto/enol tautomers of guanine: a correlated ab initio quantum chemical study

Interactions of adenine, cytosine, guanine, and thymine with Na(+), Mg(2+), and Zn(2+) cations were studied using an approximate resolution of identity correlated second-order MP2 (RI-MP2) method with the TZVPP ([5s3p2d1f/3s2p1d]) basis set. All existing tautomers of adenine, cytosine, and thymine and the eight most stable keto/enol tautomers of guanine were considered. Cations bind mostly in a bidentate manner, and stabilization energies of these complexes are larger than those in the case when cations bind in a unidentate manner. The cation...Y (Y equal to N or O) distances for divalent metals are shorter than those for Na(+) and for Zn(2+) are mostly shorter than the Mg(2+)...Y distance. The intermolecular distances between the cation and the base for complexes containing adenine and cytosine are systematically shorter than those for complexes containing guanine and thymine. Only for cytosine the canonical keto/amino tautomer structure with ions represents the global minimum. For guanine, the metalated canonical form is again the most stable, but its stabilization energy is within less than 5% of the stabilization energies of the two other rare tautomers, which indicates that the canonical form and these two rare tautomers could coexist. The canonical structures of adenine and thymine in the presence of ions are considerably less stable (by more than 10%) than the complexes of the rare tautomers. It can be concluded that the interaction of Na(+), Mg(2+), and Zn(2+) cations with cytosine in the gas phase will not induce the change of the canonical form to the rare tautomeric form. In the case of isolated guanine, the equilibrium of the canonical form with rare tautomers can be found. For isolated adenine and thymine the presence of rare tautomers is highly probable.     

氨基功能化纳米Fe3O4磁性高分子吸附剂对废水中Cr(VI)的吸附研究

采用分散聚合法通过共聚、开环反应, 对纳米Fe3O4进行表面功能化修饰, 得到富含NH2官能团的纳米磁性高分子复合材料. 通过透射电镜(TEM)、振动样品磁强计(VSM)、热重差热分析(TGA)、X射线衍射(XRD)、红外光谱(IR)等对其进行表征, 着重研究了其作为吸附剂对Cr(VI)的吸附性能. 结果表明: 该吸附剂对Cr(VI)的吸附能在10 min内达到平衡; 废水溶液pH值能显著影响吸附剂对Cr(VI)的吸附效果, pH为2.5时效果最佳. 废水中Cr(VI)的初始浓度、吸附时间、温度等因素对吸附效果均有不同程度的影响. 结合相应pH值下Cr(VI)的形态分布, 探讨了这种新型材料对Cr(VI)的吸附机理. 结果表明: 其吸附机理及吸附容量与废水中Cr(VI)的离子形式有关; 吸附过程以离子交换与静电引力为主. 等温吸附数据符合Langmuir模型, T＝308 K, pH＝2.5, V＝40 mL时, 吸附剂的饱和吸附容量qm＝25.58 mg/g. 吸附为吸热过程, 焓变ΔH＝8.64 kJ/mol.     

C9H12+·侧链分解反应机理的理论研究

正苯丙烷正离子的分解过程可以作为研究烷基苯正离子分解反应机理的原型。使用Gaussian98程序包,在B3LYP/6-311++G**基组水平上,C9H12+·分解反应系统的各反应被详细研究。用振动模式分析充分研究了各反应通道以确定过渡态,用电子布居分析讨论电子的分布并阐明反应机理。C9H12+·链反应可以由C-H键断裂而引发,但是有一个直接产生C8H9+ + CH3·的通道。     

对氨基苯甲酸热力学性质的量热和热分析研究

在80～400 K温区,用高精度全自动绝热量热仪测定了对氨基苯甲酸摩尔热容,得到摩尔热容随温度的变化的关系式为：