微型燃气轮机回热器换热表面的对比研究

采用高效紧凑式换热器是近年来微型燃气轮机发展取得成功的关键技术之一。本文在燃机参数给定情况下,通 过对三种换热表面进行热力计算和分析,结果表明,CC原表面在紧凑式换热器中具有较强的应用潜力。此外,还就温差 对压损的影响及燃气旁通量对回热度的影响进行了研究。     

Synthesis, Structure and Secondorder Nonlinear Optical Activities of a New Tungsten（0） Compound with Pyridine-2-thiolato Ligand, [Et4N][W（pyS）（CO）4] （pys = C5H4NS^-）

The reaction of W(CO)6 with pyOSNa (C5-H4NOSNa) and Et4NCl in MeCN affords a new tungsten(0) complex [Et4N][W(pyS)(CO)4] 1 (Mr.= 536.29).The crystal and molecular structures have been determined by X-ray single-crystal diffraction.Complex 1 crystallizes in the orthorhombic system,space group P212121 with a = 8.2429(5),b = 9.1045(4),c =26.8851(14) (A),β = 90.00°,V= 2017.66(18) (A)3,Z = 4,Dc.= 1.765 g/cm3,μ = 58.51 cm-1,F(000) =1048,the final R = 0.0204 and wR = 0.0400 for 4432 observed reflections with I ＞ 2σ(I).X-ray structure analysis revealed that the molecule is acentric and has large first-order hyperpolarizability (7.2 × 10-30 esu),so it could be an IR second-order nonlinear optical candidate material.     

Synthesis and Structure of Dimolybdenum Carbonyl Thiolate Compound [Et4N]2[Mo2（CO）8（SC6H4—CH3—m）2]

1 INTRODUCTION In 1984, thiolate ligand was successfully introduced into molybdenum carbonyl compound by the reaction of Mo(CO)6 with [Et4N]SR( R = C6H5, But) in a moderate condition[1]. From then on, a series of dinuclear molybdenum(0) carbonyl thiolate compounds have been synthesized and characterized by using a variety of thiolate ligands in our research group. It was found that a planar Mo2S2 unit is in the compound [Et4N]2[Mo2(CO)8(SC6H4-CH_3-p)2][2] (2) and a "butterfly" t…     

Synthesis and Crystal Structure of a Molybdenum Carbonyl Compound with Thiolate and Dithiocarbamate Ligands,[Bu4N][(OC)4Mo(μ-SC6H5)2Mo(C5H10CNS2)(CO)2]

A di-molybdenum carbonyl compound containing thiolate and dithiocarbamate li- gands, [Bu4N][(CO)4Mo(μ-SC6H5)2Mo(C5H10dtc)(CO)2] 1 (C5H10dtc = S2CNC5H10), has been pre- pared by reaction of [Mo2(SC6H5)2(CO)8] with C5H10dtcNa and [NBu4]Br in acetone. It crystallizes in monoclinic, space group P21/n with a = 13.162(3), b = 17.466(2), c = 20.453(4)(A),β = 100.77(1)°, Z = 4, V = 4619(2)(A)3, C40H56Mo2N2O6S4, Mr = 980.95, Dc = 1.389 g/cm3, μ= 7.66 cm-1, F(000) = 1988 and R = 0.0746 for 5161 observed reflections with I > 2σ(I). The complex contains a [Mo2S2]2- planar core in which one Mo atom is chelated by a C5H10dtc ligand, leading to different coordination environments of the two Mo atoms. 95Mo NMR measurement indicates that the two Mo atoms are in different oxidation states.     

Synthesis, Crystal Structure and Luminescence Property of [Ag2(dppm)2(NMP)2](SbF6)2·4H2O·3CH2Cl2

The silver-dppm complex, [Ag2(dppm)2(NMP)2](SbF6)2·4H2O·3CH2Cl2 1 (NMP = 2- (4-dimethylaminophenyl)imidazo(4,5-f)(1,10)phenanthroline, dppm = diphenylphosphinomethane), was synthesized and its structure was determined by X-ray diffraction. The crystal belongs to mono- clinic, space group C2/c, Mr = 2461.61, a = 21.57(10), b = 22.48(6), c = 22.53(6) (A), β = 101.29(2)o, V = 10713(64) (A)3, Z = 4, Dc = 1.526 g/cm3, μ = 1.141 mm-1, F(000) = 4920, R = 0.0664 and Wr = 0.1774 for 8524 observed reflections (I > 2σ(I)). Complex 1 exists as a centrosymmetric dimmer. The two dppm molecules bridge two AgNMP moieties to form an eight-membered Ag2P4C2 metal- lacyclic ring with ligand NMP chelating to each Ag. It appears photoluminescence λ(max = 625 nm) at room temperature and makes red shift compared with free ligand NMP λ(max = 522 nm). DFT calculation indicates that the emission of 1 originates from singlet metal-perturbed ILCT excited state.     

Synthesis and Structure of a New Dinuclear Molybdenum(Ⅰ)Compound with Cyclohexanthiolate Ligand,[Mo_2(SC_6H_(11)_2(CO)_8]

<正>Molybdenum( I )-compound [Mo2(SC6H11)2(CO)8] 1, crystallizes in monoclinic, space group P21/c with a = 9.5863(9), b = 9.4469(9), c = 13.869(1) A, β = 99.697(2)°, V= 1238.1(2) A3, Z = 2,DC= 1.734 g/cm3, μ = 12.23 cm-1 and F(000) = 644. The finalR = 0.0455 and wR = 0.1159 for 1590 observed reflections with I> 2σ(I). 1 possesses a rhombic bimetallic core MoS2Mo with the Mo-Mo bond length of 2.975(1) and Mo-S of 2.485(2) A.     

计算化学在分子轨道教学中的应用

分子轨道理论是理解分子电子结构与微观性质的重要理论之一,也是本科生与研究生结构化学教学中的重点与难点。学生对原子轨道组合形成分子轨道、分子轨道能级交叉混合等知识的理解缺乏形象直观、定量的认识。本文通过基于量子化学或密度泛函理论的Gaussian 03计算软件,计算、绘制并分析了F_2、O_2、N_2、HF、CO等的分子轨道能级图,将学生较难理解的内容定量、直观地呈现出来,形象地解释了分子轨道成键原则与电子填充原则等分子轨道理论中的重难点,加深了学生对分子轨道理论的理解,特别是sp轨道混杂导致的σ_(2p_z)与π_(2p)轨道能级交叉这一难点,激发了学生学习的主动性和积极性,提高了教学质量。在此基础上,利用分子轨道理论分析了CO_2的电子结构,使学生学会应用分子轨道理论解决实际问题,巩固了相关课堂理论知识。     

O与O2在Au团簇上吸附的密度泛函理论研究

采用基于密度泛函理论(DFT)的Dmol³程序系统研究了O原子与O₂在 Au₁₉与Au₂₀团簇上的吸附反应行为. 结果表明: O在Au₁₉团簇顶端洞位上的吸附较Au₂₀强; 在侧桥位吸附强度相近. O与O₂在带负电Au团簇上吸附较强, 在正电团簇吸附较弱. 从O―O键长看, 当金团簇带负电时, O―O键长较长, 中性团簇次之, 正电团簇中O―O键长较短, 因而O₂活化程度依次减弱. 电荷布居分析表明, Au团簇带负电时, O与O₂得电子数较中性团簇多, 而团簇带正电时, 得电子数较少. 差分电荷密度(CDD)表明, O₂与Au团簇作用时, 金团簇失电子, O₂的π^*轨道得电子, 使O―O键活化. O₂在Au₁₉^-团簇上解离反应活化能为1.33 eV, 较中性团簇低0.53 eV; 而在Au₁₉⁺上活化能为2.27 eV, 较中性团簇高0.41 eV, 这与O₂在不同电性Au₁₉团簇O―O键活化规律相一致.     

高比表面积Cr_2O_3-α-AlF_3催化剂的制备和应用(英文)

采用炭硬模板法制备了高比表面积Cr_2O_3-α-AIF_3催化剂.该催化剂的合成过程主要包括三步:(1)将一定浓度的蔗糖溶液浸渍到Cr_2O_3-γ-Al_2O_3中,然后经过热处理,使得蔗糖分解为炭;(2)将含炭的Cr_2O_3-γ-Al_2O_3固体在400℃用HF气体进行完全氟化;(3)在高温下利用燃烧法除去炭硬模板.对所制备的催化剂进行了X射线衍射(XRD),氮气吸脱附曲线,氨气程序升温脱附(NH_3-TPD),透射电镜(TEM),扫描电镜(SEM)和X射线能量散射(EDX)技术表征.结果表明,氟化过程对Cr_2O_3-α-AIF_3催化剂比表面积有重要影响,在最佳实验条件下,能够得到比表面积为115 m~2·g~(-1)的催化剂.此催化剂对催化裂解二氟乙烷(HFC-152a)制备氟乙烯(VF)的催化活性明显高于直接氟化制备的Cr_2O_3-α-AIF_3催化剂,这是因为高比表面积的Cr_2O_3-α-AIF_3催化剂具有较大的酸量.     

Studies,on the synthesis,structure, IR spectra and reactivity of a new dinuclear Mo(0) complex, [Et4N]2[Mo2(CO)8(SCH2CO2Et)2]

Reaction of Et₄NI, NaSCH₂CO₂Et and Mo(CO)₆ in CH₃CN affords a new dinuclear molybdenum (0) complex, [Et₄N]₂[Mo₂(CO)₈(SCH₂CO₂Et)₂] (1). Electrochemistry and reactivity investigation indicate that 1 undergoes an interesting two-electron oxidation in a single step (-0.43 V) and a substitution of its carbonyls by coordinating solvents resulting in two kinds of Mo(I)-complexes, Mo₂(CO)₈(SCH₂CO₂Et)₂ and (Mo₂(CO)₆SCH₂CO₂Et)₂(CH₃CN)₂. vC=O and vMo-CO have been assigned. The crystal and molecular structure has been determined from three-dimensional X-ray data. 1 crystallized in the triclinic, space group with a=10.362(1), b=10.391(1), c= 10.815(2)Å; α=91.64(2)°, β=100.07(2)°, γ=114.46(1)°; Z=1; R=4.8% for 2975 reflections with I>3σ(I). Nonbonding of Mo … Mo [3.939(1)Å] and the configuration of MoS₂Mo unit in 1 are very different from those in related Mo(I)-product. These results confirm our previous speculation that the two-electron character derives from creation or cleavage of a metal-metal single bond coupled with structural rearrangement in a bridged bimetallic center.