Ab Initio Studies on Eight Electronic States of the BH_2 Radical

The present paper covers ab initio UHF calculations with a d, p-polarized basis set performed for eight electronic states of BH2 and the equilibrium geometries, electronic term values Tc and vibrational frequencies of the five stable states X2A1, 2B1, 2B2, 22A1 and 2A2. On the basis of the UHF results, the states 22B2. 2B1 and 32A1 are predicted to be unstable. The MP2/6-31G * * calculations were performed for the X2A1 and 2B1, states, and the calculated equilibrium geometries, Tc value and vibrational frequencies are similar to the UHF results. The MP2/6-31G * * studies on the reaction BH2→BH + H for the X2A1 and 2B1 states were carried out and the HB-H bond energies of these two states were calculated.     

Theoretical Studies on the Intermonomer Interaction of F~-·(H_2O)_n (n = 1, 2)

1 INTRODUCTION Hydrogen bond plays an important role in the fields of physics, biology and chemistry. It has cap- tured the interest of chemists for a long time and reports about its theory and experiment have been well represented[1～6]. Concerning its theoretical inves- tigations, most of the emphases are placed on the weak interaction energy of intramolecular hydrogen bond. But studies on its spectrum behavior are rela- tively rare. These years spectrum behavior led by hydrogen bond h…     

Ab initio Studies on the Reaction of M~ CH_4→M~ CH_2 H_2(M＝Sc,Y,La)

ＡｂｉｎｉｔｉｏＳｔｕｄｉｅｓｏｎｔｈｅＲｅａｃｔｉｏｎｏｆＭ~＋＋ＣＨ_４→Ｍ~＋ＣＨ_２＋Ｈ_２（Ｍ＝Ｓｃ，Ｙ，Ｌａ）ＺＨＵＲｏｎｇ－ｓｈｕｎ；ＤＡＩＳｈｕｓｈａｎ；ＨＵＡＮＧＪｉａｎ－ｈｕａａｎｄＹＥＳｏｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔ?..     

Ab Initio Molecular Orbital Calculation on Dinuclear Gold(Ⅰ)Complexes──Metal-Metal Interaction and Electronic Structure of Binuclear Gold(Ⅰ)Complexes with Bridging Bidentate Ligands

ＡｂＩｎｉｔｉｏＭｏｌｅｃｕｌａｒＯｒｂｉｔａｌＣａｌｃｕｌａｔｉｏｎｏｎＤｉｎｕｃｌｅａｒＧｏｌｄ（Ⅰ）Ｃｏｍｐｌｅｘｅｓ——Ｍｅｔａｌ┐ＭｅｔａｌＩｎｔｅｒａｃｔｉｏｎａｎｄＥｌｅｃｔｒｏｎｉｃＳｔｒｕｃｔｕｒｅｏｆＢｉｎｕｃｌｅａｒＧｏｌｄ（Ⅰ...     

Self-assembly of Bis[2-(2-hydroxyphenyl)-pyridine]Copper(Ⅱ) Induced by C-H…π and π…π Stacking Interaction

Introduction The control of molecular assembly in the solid state is an important theme of modern chemistry.It is in this regard that there is an activity in the area of supramolecular structures at present.The self-assembly of molecules can form well-defined supramolecular structures under the influence of drive forces such as hydrogen bonds[1-3],metal-ligand coordination bonds[4-6] and π…π stacking interactions[7-10].Word et al.have described the co-ordination chemistry of polydentate chelating ligands which contain mixed pyridine-phenol donor sets[11].Some unusual structures of transition metal pyridine-phenol complexes have been established in which non-covalent interactions such as hydrogen bonding and π…π stacking appear to play a dominant part.These observations suggest that it might be possible to construct supramolecular structures with a metal pyridine-phenol system.To explore this idea we have begun to investigate the self-assembly properties of metal pyridine-phenol complexes.Herein we present the self-assembly properties of Cu(pp)2[pp=2-(2-hydroxyphenol)-pyridine] under different conditions.     

Crystal Structure and Interaction with DNA of [Ni(phen)(mal)(H_2O)_2]·3H_2O

1 INTRODUCTION In the last few years, much attention has been paid to the molecular structure and biological activity of coordinated complexes in inorganic chemistry field. Ni(Ⅱ) is one of the commonest transition metals with two coordination numbers (4 and 6)[1～3]. Ge- nerally speaking, Ni(Ⅱ) coordination mode depends on the structure of ligand, solvent and reaction con- ditions, among which ligand plays a decisive role and determines not only the molecular structure of the complex bu…     

Synthesis and Quantum Chemistry Studies of (R)-N-(Propionylthiazolidine-2-thione-4-methoxycarbonyl)germanium Sesquioxide

ＳｙｎｔｈｅｓｉｓａｎｄＱｕａｎｔｕｍＣｈｅｍｉｓｔｒｙＳｔｕｄｉｅｓｏｆ（Ｒ）┐Ｎ┐（Ｐｒｏｐｉｏｎｙｌｔｈｉａｚｏｌｉｄｉｎｅ┐２┐ｔｈｉｏｎｅ┐４┐ｍｅｔｈｏｘｙｃａｒｂｏｎｙｌ）ｇｅｒｍａｎｉｕｍＳｅｓｑｕｉｏｘｉｄｅ＊ＬＩＹｅ－ｚｈｉ＊＊,...     

Synthesis and Crystal Structure of a Three-dimensional Manganese(Ⅱ)Complex (tataH)2[Mn(pydc)2]·4H2O(tata= 2,4,6-Triamino-1,3,4,-triazine,pydcH2= Pyridine-2,6-dicarboxylic Acid)

A manganese(Ⅱ) complex (tataH)2[Mn(pydc)2]·4H2O (C20H28MnN14O12, Mr = 711.50, tata = 2,4,6-triamino-1,3,5-triazine, pydcH2 = pyridine-2,6-dicarboxylic acid) has been synthesized and its crystal structure was determined by single-crystal X-ray diffraction. The crystal belongs to the triclinic system, space group P1, with a = 9.9847(3), b = 10.9813(3), c = 15.2616(5) (A), α =101.5310(10), β = 90.2610(10), γ = 116.4600(10)°, V = 1459.44(8) A3, Z = 2, Dc = 1.619 g/cm3, μ = 0.539 mm-1, F(000) = 734, the final R = 0.0292 and wR = 0.0745. In the crystal the MnⅡ atom is six-coordinated by four carbonyl oxygen atoms and two pyridine nitrogen atoms from two tridentate H-bonded tetramer. The molecules are packed in a three-dimensional framework structure by the combination of O-H…O,N-H…O and N-H…N hydrogen bonds between (tataH) ,[Mn(pydc)2]2- and crystal water.     

Synthesis, Crystal Structure and Electrochemical Studies of Two Novel Zn(II) Complexes of Phthalic Acid and Imidazole Derivatives

Two novel coordination polymers [Zn(pa)(vim)2]n (1) and [Zn(pa)(eim)2]n (2) (pa＝phthalic acid dianion, vim＝1-vinyl-1H-imidazole, eim＝1-ethyl-1H-imidazole) have been synthesized and their structures characterized by X-ray single crystal diffractometry and elemental analysis. Both of the complexes consist of [Zn(L)2] (L＝vim for 1; eim for 2) entities linked into polymeric zigzag chains along the crystallographic c-axis by bridging phthalate anions in the μ2-1,2 coordination mode. The coordination around each Zn(II) atom is tetrahedral. There are only van der Waals interactions between the chains in 1, while the three-dimensional network in 2 is assembled by C—H…O contacts. The electrochemical studies reveal that redoxes of Zn2+/Zn in complexes 1 and 2 are irreversible processes.     

Does the molecular structure of CaH2 affect the dihydrogen bonding in CaH2 … HY (Y = CH3, C2H3, C2H, CN, and NC) complexes? A quantum chemistry study using MP2 and B3LYP methods

Second-order M ller-Plesset(MP2) and density functional theory(DFT) calculations have been carried out in order to investigate the structures and properties of dihydrogen-bonded CaH 2 HY(Y = CH 3,C 2 H 3,C 2 H,CN,and NC) complexes.Our calculations revealed two possible structures for CaH 2 in CaH 2 HY complexes:linear(I) and bent(II).The bond lengths,interaction energies,and strengths for H H interactions obtained by both MP2 and B3LYP methods are quite close to each other.It was found that the interaction energy decreases with increasing electron density at the Ca-H bond critical point.Atom-in-molecule(AIM) results show that for all of Ca-H H-Y interactions considered here,the Laplacian of the electron density at the H H bond critical point is positive,indicating the electrostatic nature of these Ca-H H-Y dihydrogen bonded systems.     

甲醛与乙醛,甲醚,硝基甲烷相互作用的从头算研究

用6-31G、全构型优化,研究了甲醛与乙醛、甲醚、硝基甲烷的相互作用。结果表明所有超分子稳定构型都包含2个C—H—O氢键的平面环状结构。H—O距离为0.228～0.264 nm,作用能为—19～—24 kJ/mol,与二聚水的作用能接近。稳定性主要取决于甲基上取代基Y吸电子能力以及环状结构中氢键张力。STO-3G不很适用于研究这类分子的相互作用。     

OCH＝CHR（R＝H，BH_2，CN，F，OH，NH_2）自由基结构和稳定性的ab initio研究

用ＵＨＦ／４－３１Ｇ基组，全构型优化ＯＣＨＣＨＲ（Ｒ＝Ｎ，ＢＨ_２，ＣＮ，Ｆ，ＯＨ，ＮＨ_２）６个氧自由基的构型并研究其稳定化能△Ｅ。以ＯＣＨＨ_２自由基为参考标准，它们的△Ｅ分别为０．００、－７５．９７、１．１１、０．７６、２２．０６和４０．６５ｋＪ／ｍｏｌ，说明供电子基团ＯＨ和ＮＨ_２对氧自由基起稳定化作用，ＢＨ_２对氧自由基起去稳定化作用，而ＣＮ和Ｆ对氧自由基的稳定性影响不大。     

HXLiF（X=B,Al）分子几何构型的从头算

用从头算方法研究类硼烯ＨＢＬｉＦ和类铝烯ＨＡ１ＬｉＦ的几何构型，它们均有四种平衡构型，分析各构型的特点，从Ｍｕｌｌｉｋｅｎ集居数和分子间相互作用的角度讨论其稳定性，并与Ｈ２ＣＬｉＦ、Ｈ２ＳｉＬｉＦ和ＨＮＬｉＦ进行了比较。     

HPXF(X=Li,Na)的构型及反应性能的从头算研究

用RHF/6-31G^*从头算解析梯度法优化了类磷烯HPXF(X=Li,Na)的平衡构型,分析了各构型的结构特点及稳定性.通过与磷烯(¹HP)相比较,探讨了HPXF(X=Li,Na)的反应活性,还简单讨论了碱金属原子对HPXF(X=Li,Na)三元环构型稳定性和反应活性的影响.结果表明,HPLiF和HPNaF均具有3种平衡构型,其中三元环构型最稳定,也是参加反应的基本构型:类磷烯与相应的¹HP相比,可成为一种使反应容易控制、选择性好和易获得的亲电反应中间体.     

碱金属烯醇盐的从头算

在RHF／3－21GRHF／321G,RHF／6-31＋G,MP2／6－31＋G,RHF／lanl2dz,MP2／lanl2dz和MP2／6－31＋G水平上,对CH2＝CH（OM）（M＝Li,Na,K,Rb,C。）进行了研究．结果表明,所有化合物都有平面式和非平面桥式两种构型.结构参数、自然轨道布局分析和反应热均反映出碱金属对烯酸负离子的共振有很大程度的限制,不同的碱金属盐差别不十分明显．     

Ab Initio Study on The Influence of Spin State upon Bonding,Interaction in Fe—CO

Four Fe—CO states with 3d_σ-4s, 3d_δ-3d_δ electrons spin-paired or spinunpaired were examined to investigate the influences of pairing versus unpairing mechanisms upon the bonding, interaction in Fe—CO. The calculation results show that the Fe—CO bonding, interaction are determined by a balance between the bonding stabilization, the exchange stabilization with 3d_σ-4s electron spinpairing or without it. The 3d_δ-3d_δ electron spinpairing versus unpairing has a surprised effect on the Fe—CO bonding properties even though the 3d_δ orbitals are usually considered as non bonding ones.     

精密从头算与ABEEM/MM模型对水团簇(H2O)11 9种低能结构的计算

用精密从头算方法研究了(H2O)11的9种低能异构体的性质, 包括优化的几何结构、结合能、偶极矩和氢键个数等, 并且得出了515-a是(H2O)11的全局最低能结构. 同时, 也用ABEEM/MM(atom bond electronegativity equalization method/molecular mechanics) 模型研究了这些性质, 与从头算的结果进行了比较, 得到了相符合的结果. 这显示了ABEEM/MM模型在描述中等大小的水分子团簇结构上是成功的.     

Experimental and Ab Initio Equilibrium Structures of cis-Thionylimide,HNSO: Estimation of the Laurie Correction

The equilibrium structure of cis-thionylimide, HNSO has been determined using high-level ab initio calculations and various experimental procedures. The Laurie correction to the N-H bond length is discussed and it is shown that it can be estimated by ab initio methods. The results are found to be in good agreement and the best equilibrium structure is (in Å for the bond lengths): r(N–H) = 1.020(1), r(N–S) = 1.510(2), r(S–O) = 1.448(1), (HNS) = 115.94(39)°, and (NSO) = 120.44(10)°.     

CH3F分子间相互作用的ab initio研究

在MP2/6-311+ +G(3d,3p)电子相关校正水平上,对CH₃F二聚体可能存在的几何构型进行全自由度能量梯度优化和频率验证,发现3种势能面上有极小点的构型.进一步在高级电子相关校正的MP4S-DTQ、CCSD(T)/6-311+ +G(3df,3pd)方法水平上,对其中总能量最小的构型进行精确计算,得到二聚体的结合能为-9.707kJ/mol.研究结果支持了由光谱实验结果推测的构型,解释了CH₃F二聚体的谐振频率的多样性.     

Ab Initio Study on the Potential Energy Surfaces of B4 Cluster

The singlet and triplet potential energy surfaces (PES) for the isomerization and dissociation reactions of B₄ isomers have been investigated using ab initio methods. Ten B4 isomers have been identified and of these 10 species, 4 have not been reported previously. The singlet rhombic structure ¹1 is found to be the most stable on the B₄ surface, in agreement with the results of previous reports. Several isomerization and dissociation pathways have been found. On the singlet PES, the linear ¹3b can rearrange to rhombus ¹1 directly, while ¹3c rearranges to ¹1 through two‐step reactions involving a cyclic intermediate. On the triplet PES, the capped triangle structure ³2 undergoes ring opening to the linear isomer ³3b with a barrier of 34.8 kcal/mol and 44.9 kcal/mol, and the latter undergoes ring closure to the square structure ³1 with a barrier of 30.4 kcal/mol and 33.0 kcal/mol at the MP4/6–311+G(3df)//MP2/6–311G(d) and CCSD/aug‐cc‐pVTZ//MP2/6–311G(d) levels of theory, respectively. The direct decomposition of singlet B₄ yielding to B₃+B is shown to have a large endothermicity of 87.3 kcal/mol (CCSD), and that producing 2B₂ to have activation energy of 133.4 kcal/mol (CCSD).