1-异丙基环己硅烷类液晶化合物的量子化学研究--取代联苯基乙烷系列

我们曾用半经验的分子轨道方法对标题化合物的某些系列进行过计算[1 ,2 ] 。本文选择 7种 1 异丙基环己硅烷 取代联苯基乙烷系列化合物 ,以ＳＣＦ—ＭＯ—ＡＭ1 [3] 和ＰＭ3[4] 两种方法 ,优化出它们稳定的几何构型 (分子的总能量最低、核—核排斥能最小 )并对其作了振动分析 ;同时计算了标题物在该稳定构型下的电子结构和若干基本性质。1　计算图 1示出了 7种标题化合物的结构及原子编号。用ＭＯＰＡＣ7.0程序中的ＡＭ1 和ＰＭ3方法 ,分子的初始构型参数采用Ｐｏｐｌｅ’ｓ标准构型数据[5] 。对每个分子实行能量梯度全优化和ＳＣＦ计算。…     

相转移催化合成对甲氧基肉桂酸-2-乙基己酯的研究

对甲氧基肉桂酸 2 乙基己酯是一种有效的ＵＶＢ防晒剂[1 ,2 ] ,一般采用Ｃｌａｉｓｅｎ Ｓｃｈｍｉｄｔ缩合反应制得[3] ,但由于催化剂ＫＯＨ处于水相 ,对反应物不能充分起到催化作用导致产率较低[4] 。我们利用乙二醇 (ＰＥＧ)为相转移催化剂合成立体专一的反式对甲氧基肉桂酸 2 乙基己酯 ,产率提高到 72 .5 %。合成路线如下 :1　实验部分1 .1　仪器与试剂ＢＩＯ ＲＡＰＦＴ45 0红外光谱仪 ,用液膜法测试 ;Ｂｒｕｒｅｒ ＡＭ 30 0超导核磁共振仪 (溶剂ＤＣ Ｃｌ3) ;ＭＡＴ/44Ｓ ,ＧＣ ＭＳ型色质联用谱仪 ;试剂均为分析纯 ,上海化学试剂…     

硫化态Mo/γ-Al2O3催化剂活性位的低温CO-FTIR方法表征及噻吩HDS活性

ＭｏＳ2 是钼基加氢精制催化剂 [Ｃｏ(Ｎｉ)Ｍｏ/γ Ａｌ2 Ｏ3]活性相的主要组份 ,其形态与结构对Ｃｏ(Ｎｉ)Ｍｏ/γ Ａｌ2 Ｏ3的加氢脱硫 (ＨＤＳ)、加氢脱氮 (ＨＤＮ)活性的影响至关重要[1 ,2 ] .目前 ,人们通常使用的ＴＰＲ方法虽可测定过渡金属硫化物的表面活性位 ,并可有效地区分位于催化剂活性相 (ＭｏＳ2 ｓｌａｂ)周边的硫物种 ,但对不同价态的钼尚无法鉴别[3] .本文制备了硫化态Ｍｏ/γ Ａｌ2 Ｏ3催化剂 ,以ＣＯ为探针分子 ,利用ＦＴＩＲ技术在液氮温度 (77Ｋ)下考察了催化剂的表面活性位 (钼物种 )及催化噻吩ＨＤＳ的活性 .1　实…     

Synthesis and Crystal Structure of （1,3—^tBu2C5H3）2Sm（μ—Cl）2Li（THF）2

1　ＩＮＴＲＯＤＵＣＴＩＯＮＡｓａｔｙｐｅｏｆｉｍｐｏｒｔａｎｃｅｐｒｅｃｕｒｓｏｒ,ａｌｏｔｏｆｏｒｇａｎｏｌａｎｔｈａｎｉｄｅｃｈｌｏｒｉｄｅｃｏｍｐｌｅｘｅｓｈａｖｅｂｅｅｎｓｙｎｔｈｅｓｉｚｅｄａｎｄｓｔｒｕｃｔｕｒａｌｌｙｃｈａｒａｃｔｅｒｉｚｅｄ[1].Ｔｈｅｂｉｍｅｔａｌｌｉｃｃｏｍｐｌｅｘｅｓｃｏｎｔａｉｎｉｎｇａｌｋａｌｉｍｅｔａｌ,Ｃｐ2Ｌｎ(μＣｌ)2Ｍ(Ｌ)(Ｃｐ=η5Ｃ5Ｈ5ｏｒＣ5Ｍｅ5;Ｍ=Ｌｉ,Ｎａ;Ｌ=ＴＨＦ,ＴＭＥＤＡ),ｉｓａｍａｉｎｓｔｒｕｃｔｕｒｅｔｙｐｅ.Ｉｎｔｈｅｃｏｕｒｓｅｏ…     

壳聚糖吸附Cd2+的机理

壳聚糖分子中的大量氨基及部分酰胺基的存在 ,能够选择性地配位或吸附一些金属离子 ,尤其是对过渡金属离子具有较好的螯合能力。Ｐｉｒｏｎ等[2 ] 利用放射性85Ｓｒ研究了壳聚糖的氨基与碳酸锶离子对Ｓｒ2 +、ＣＯ2 -3 之间形成的三元络合物的结构。季君晖[3] 通过光电子能谱研究发现 :壳聚糖螯合Ｃｕ2 +,只与壳聚糖中的—ＮＨ2 配位。Ｔｓｅｚｏｓ[4] 利用ＩＲ、ＭＳ和ＥＰＲ说明铀与壳聚糖的络合点为氨基的氮原子。Ｇｕｉｂａｌ等[5] 用ＩＲ、ＣＰ ＭＡＳ1 3ＣＮＭＲ及反射光谱法证实吸附机理涉及氨基。含镉废水是危害较大的工业废水之一 …     

Synthesis and structure of {Mo_3S_7[S_2P(OC_2H_5)_2]_3}{Mo_3S_4[S_2P(OC_2H_5)_2]_4(SCN)} and interaction between their cluster units

Ｔｈｅｔｒｉｍｏｌｙｂｄｅｎｕｍｃｌｕｓｔｅｒｓｗｉｔｈｇｅｎｅｒａｌｆｏｒｍｕｌａ[Ｍｏ3(μ3Ｓ)(μＳ)3(μｄｔｐ)(ｄｔｐ)3Ｌ](ｄｔｐ=(Ｓ2Ｐ(ＯＣ2Ｈ5)2)-,Ｌ=Ｈ2Ｏ,ｐｙ,ＳＣ(ＮＨ2)2ｅｔｃ.)[1](ｒｅｆｅｒｒｅｄｔｏａｓＭ1ｔｙｐｅ[2]),ａｎｄ[Ｍｏ3(μ3Ｓ)(μＳ2)3(ｄｔｐ)3]Ｘ(Ｘ=Ｃｌ,Ｉ)[3](ｒｅｆｅｒｒｅｄｔｏａｓＭ2ｔｙｐｅ),ａｒｅｔｗｏｍａｉｎｔｙｐｅｓｏｆｔｒｉｍｏｌｙｂｄｅｎｕｍｃｌｕｓｔｅｒｓｅｖｅｒｉｎｖｅｓｔｉｇａｔｅｄｂｙｏｕｒｒｅｓｅａｒｃｈｇｒｏｕｐ.Ａｓｗｅｈａｖｅａｌｒｅａｄｙ…     

Synthesis and Structure of Barium Complex Containing 2,2,6,6-Tetramethyl-3,5-heptanedionate and 1,10-Phenanthroline Ligands

1　ＩＮＴＲＯＤＵＣＴＩＯＮＭｅｔａｌ ｏｒｇａｎｉｃｃｈｅｍｉｃａｌｄｅｐｏｓｉｔｉｏｎ(ＭＯＣＶＤ)ｉｓａｎａｐｐｅａｌｉｎｇｔｅｃｈｎｉｑｕｅｆｏｒｅｌｅｃ ｔｒｏｎｉｃａｐｐｌｉｃａｔｉｏｎｓ.ＡｓｏｎｅｏｆｔｈｅＭＯＣＶＤｓｏｕｒｃｅｍａｔｅｒｉａｌｓｆｏｒＹＢＣＯｓｕｐｅｒｃｏｎｄｕｃｔｏｒｆｉｌｍｓ,ｂｉｓ( 2 ,2 ,6,6 ｔｅｔｒａｍｅｔｈｙｌ 3,5 ｈｅｐｔａｎｅｄｉｏｎａｔｅ)ｂａｒｉｕｍｈａｓｂｅｅｎｅｘｔｅｎｓｉｖｅｌｙｕｓｅｄｉｎｔｈｅｐａｓｔ[1～ 3].Ｔｈｅｌａｒｇｅｓｉｚｅｏｆｔｈｅ…     

核酸四碱基体的量子化学计算

应用量子化学半经验ＣＮＤＯＭＯ方法，对核酸碱基间可能形成的四碱基体进行计算．结果显示，除了实验中已确认存在的两种四碱基体Ｇ４和Ｇ·Ｃ·Ｇ·Ｃ外，还有６种以Ｗａｔｓｏｎ－Ｃｒｉｃｋ碱基对形成的四碱基体也能稳定存在．通过对Ｇ４碱基体分子间、离子－分子间相互作用的考查，进一步证实了氢键、四碱基体间的堆积作用、金属离子与四碱基体的相互作用等，对于四螺旋核酸结构的形成是重要的．     

镧与L-酪氨酸和甘氨酸三元固态配合物的热化学研究

由于稀土元素镧与氨基酸形成的配合物具有抗癌、抗肿瘤活性 ,人们对稀土氨基酸配合物的研究产生了浓厚兴趣。有关这类配合物的制备和表征的研究较多[1～ 4] ,而对其热化学性质的研究较少。我们按文献[5] 方法合成了配合物Ｌａ(Ｔｙｒ)(Ｇｌｙ) 3Ｃｌ3·3Ｈ2 Ｏ(ｓ) ,在自行研制的具有恒定温度环境反应热量计上 ,分别测定了Ｌａ2 Ｏ3(ｓ)、氨基酸 [Ｌ 酪氨酸 (Ｌｙｒ) +甘氨酸 (Ｇｌｙ) ]和配合物在2ｍｏｌ·Ｌ- 1 ＨＣｌ溶液中的溶解焓 ,通过设计的热化学循环得出配合反应焓 ,进而计算出Ｌａ(Ｔｙｒ)(Ｇｌｙ) 3Ｃｌ3·3Ｈ2 Ｏ(ｓ)的标准摩尔…     

《有机化学》第四届编辑委员会

主　编 (Ｅｄｉｔｏｒ ｉｎ Ｃｈｉｅｆ)陈庆云 (ＣＨＥＮＱｉｎｇ Ｙｕｎ)副主编 (ＡｓｓｏｃｉａｔｅＥｄｉｔｏｒｓ ｉｎ Ｃｈｉｅｆ)(按姓氏笔划排序 )邓敏智 (ＤＥＮＧＭｉｎ Ｚｈｉ)　　　　　吴厚铭 (ＷＵＨｏｕ Ｍｉｎｇ)伍贻康 (ＷＵＹｉ Ｋａｎｇ)林国强 (ＬＩＮＧｕｏ Ｑｉａｎｇ)吴世晖 (ＷＵＳｈｉ Ｈｕｉ)荣国斌 (ＲＯＮＧＧｕｏ Ｂｉｎ)顾　问 (Ａｄｖｉｓｏｒ)黄耀曾 (ＨＵＡＮＧＹａｏ Ｚｅｎｇ)编辑委员会委员 (ＭｅｍｂｅｒｓｏｆＥｄｉｔｏｒｉａｌＢｏａｒｄ)　(按姓氏笔划排序 )　　　　　　马大为 (ＭＡＤａ Ｗｅｉ)…     

More user-friendly phosphines? Molecular structure of methylphosphine and its adduct with borane, studied by gas-phase electron diffraction and quantum chemical calculations

The molecular structures of methylphosphine (CH(3)PH(2)) and methylphosphine-borane (CH(3)PH(2).BH(3)) have been determined from gas-phase electron diffraction data and rotational constants, employing the SARACEN method. The experimental geometric parameters generally showed a good agreement with those obtained using ab initio calculations and previous microwave spectroscopy studies. In order to assess the accuracy of the calculated structures a range of ab initio methods were used, including the CCSD(T) method, with correlation-consistent basis sets. The structural environment around the phosphorus atom was found to change significantly upon complexation with borane, with the P-C bond length shortening and the bond angles widening.     

Small gaussian basis sets for AB initio calculations on large molecules

Gaussian basis sets of (5s, 2p) for carbon, nitrogen, and oxygen, and (7s, 4p) for phosphorous and sulfur have been developed for ab initio calculations of biological molecules. Double zeta contracted bases are given for all five atoms. Minimum bases are given for carbon, nitrogen and oxygen, and a method is developed for replicating primitives in order to minimize the energy loss when contracting small bases. The contracted bases are applied to formamide and the results are compared with those obtained from other small basis sets.     

Intermolecular electrostatic energies using density fitting

A method is presented to calculate the electron-electron and nuclear-electron intermolecular Coulomb interaction energy between two molecules by separately fitting the unperturbed molecular electron density of each monomer. This method is based on the variational Coulomb fitting method which relies on the expansion of the ab initio molecular electron density in site-centered auxiliary basis sets. By expanding the electron density of each monomer in this way the integral expressions for the intermolecular electrostatic calculations are simplified, lowering the operation count as well as the memory usage. Furthermore, this method allows the calculation of intermolecular Coulomb interactions with any level of theory from which a one-electron density matrix can be obtained. Our implementation is initially tested by calculating molecular properties with the density fitting method using three different auxiliary basis sets and comparing them to results obtained from ab initio calculations. These properties include dipoles for a series of molecules, as well as the molecular electrostatic potential and electric field for water. Subsequently, the intermolecular electrostatic energy is tested by calculating ten stationary points on the water dimer potential-energy surface. Results are presented for electron densities obtained at four different levels of theory using two different basis sets, fitted with three auxiliary basis sets. Additionally, a one-dimensional electrostatic energy surface scan is performed for four different systems (H2O dimer, Mg2+-H2O, Cu+-H2O, and n-methyl-formamide dimer). Our results show a very good agreement with ab initio calculations for all properties as well as interaction energies.     

An ab initio method for performing valence-electron-only calculations

We present a new method for performing valence-electron-only calculations on systems containing heavy atoms. The method contains no adjustable parameters and when used with a large orbital basis set yields exactly the same valence electron energy as an all-electron ab initio calculation. Good results are also obtained with truncated orbital basis sets.     

Study of locally dense and locally saturated basis sets in localized molecular orbital calculations of nuclear shielding: Ab initio LORG calculations for 13C and 17O in norbornenone

This study demonstrates the use of uneven atomic basis sets for ab initio calculations of NMR shielding in the localized orbital/local origin (LORG) approach with norbornenone as the test case. We distinguish between locally dense sets (extended basis on target atom only) and locally saturated sets (extended bases on target atom and atoms in its first bonding sphere), using 6-311G ** and 6-31G sets to describe the high and low level of function sets. It is shown that the use of these uneven sets can simulate high basis set level calculations of shieldings for ¹H and for all the ¹³C nuclei in this molecule and, hence, allows quite accurate ab initio calculations of shielding properties of these nuclei in large molecules using relatively modest computational facilities. The shielding of the double-bonded ¹⁷O nucleus is apparently sensitive to basis-set quality beyond the first bonding sphere. © 1996 John Wiley & Sons, Inc.     

Conformations and energetics of sulfur and selenium diimides

The geometries and energetics of different conformations of sulfur and selenium diimides E(NR)(2) (E = S, Se; R = H, Me, (t)Bu, C(6)H(3)Me(2)-2,6, SiMe(3)) have been studied by using various ab initio and DFT molecular orbital techniques. The syn,syn conformation is found to be most stable for parent E(NH)(2), but in general, the preferred molecular conformation for substituted chalcogen diimides is syn,anti. In the case of E(NH)(2) the present calculations further confirm that syn,syn and syn,anti conformations lie energetically close to each other. From the three different theoretical methods used, B3PW91/6-31G proved to be the most suitable method for predicting the geometries of chalcogen diimides. The optimized geometrical parameters are in a good agreement with all available experimental data. While qualitative energy ordering of the different conformations is independent of the level of theory, the quantitative energy differences are dependent on the method used. The performance and reliability of higher level ab initio calculations and DFT methods using large basis sets were tested and compared with experimental information where available. All of the higher level ab inito methods give very similar results, but the use of large basis sets with the B3PW91 method does not increase the reliability of the results. The combination of CCSD(T)/cc-pVDZ with the B3PW91/6-31G-optimized geometries is found to be the method of choice to study energetic properties of chalcogen diimides.     

Ab initio conformation analysis of ouabain and ouabagenin molecules

Full conformation analysis of molecules of cardiotonic steroids ouabain and ouabagenin was performed. Full ab initio optimization of the geometric parameters of all the possible conformations of these molecules was made. The calculations were performed by the restricted Hartree Fock method in the 6–31G* basis set using GAMESS program. The effect of various factors on the steric and electronic structure of ouabain and ouabagenin was analyzed. The major factor affecting the geometric and electronic structure of ouabain and ouabagenin molecules is the conformation of ring A of the steroid core.     

Conformational stability, structural parameters and vibrational assignment from variable temperature infrared spectra of krypton solutions and ab initio calculations of ethylisothiocyanate

Variable temperature (-105 to -150 degrees C) studies of the infrared spectra (3500-400 cm(-1)) of ethylisothiocyanate, CH(3)CH(2)NCS, dissolved in liquid krypton have been recorded. Additionally the infrared spectra of the gas and solid have been re-investigated. These spectroscopic data indicate a single conformer in all physical states with a large number of molecules in the gas phase at ambient temperature in excited states of the CN torsional mode which has a very low barrier to conformational interchange. To aid in the analyses of the vibrational and rotational spectra, ab initio calculations have been carried out by the perturbation method to the second order (MP2) with valence and core electron correlation using a variety of basis sets up to 6-311+G(2df,2pd). With the smaller basis sets up to 6-311+G(d,p) and cc-PVDZ, the cis conformer is indicated as a transition state with all larger basis sets the cis conformer is the only stable form. The predicted energy difference from these calculations between the cis form and the higher energy trans conformer is about 125 cm(-1) which represents essentially the barrier to internal rotation of the NCS group (rotation around NC axis). Density functional theory calculation by the B3LYP method with the same basis sets predicts this barrier to be about 25 cm(-1). By utilizing the previously reported microwave rotational constants with the structural parameters predicted by the ab initio MP2(full)/6-311+G(d,p) calculations, adjusted r(0) structural parameters have been obtained for the cis form. The determined heavy atom parameters are: r(NC)=1.196(5), r(CS)=1.579(5), r(CN)=1.439(5), r(CC)=1.519(5)A for the distances and angles of angleCCN=112.1(5), angleCNC=146.2(5), angleNCS=174.0(5) degrees . The centrifugal distortion constants, dipole moments, conformational stability, vibrational frequencies, infrared intensities and Raman activities have been predicted from ab initio calculations and compared to experimental quantities when available. These results are compared to the corresponding quantities of some similar molecules.     

Theoretical calculation of electrode potentials: Electron-withdrawing compounds

The electrode potential of 2,3-dicyanobenzoquinone in aqueous solution has been calculated relative to parabenzoquinone using a thermodynamic cycle approach that includes accurate gasphase ab initio calculations and calculation of differences in free energies of hydration using the free-energy perturbation method. The discrepancy between the calculated and experimental electrode potential is disappointingly large (99 mV) compared to previous studies using this approach. This, along with the experimental evidence, suggests that the experimental value itself is too large and that theoretical approaches may indeed be as reliable as experimental ones for determining redox properties of molecules such as 2,3-dicyanobenzoquinone. In the light of this discrepancy we have examined the variation of the results with the basis set, inclusion of electron correlation and changes in the parameters used in the molecular dynamics free-energy simulations. The results are shown to be dependent upon the torsional parameters and especially dependent upon the basis set or semiempirical method used to obtain the electrostatic potential-derived charges. The best charge set was determined using the ab initio criteria of completeness—as far as it can be applied to large molecules—and also by studying the effect of hydration on these charges. This was done by allowing the solvent to perturb the wave function prior to the electrostatic potential determination. Thus, 3-21G and 6-31G * basis sets were found to give satisfactory results. Similar results were obtained using semiempirical and ab initio geometries.