HO2自由基与NO2反应通道的理论研究

应用密度泛函理论DFT/B3LYP对HO₂＋NO₂反应进行了研究, 在B3LYP/6-311G^**和CCSD(T)/6-311G^**水平上计算了HO₂自由基与NO₂分子反应的单重态和三重态反应势能面, 计算结果表明, 单重态反应势能面中的直接氢抽提反应机理是此反应的主要反应通道, 即HO₂自由基的氢原子转移到NO₂分子的氮原子上形成产物P₁ (HNO₂＋³O₂), 另一个可能的反应通道是单重态反应势能面上HO₂中的端位氧原子进攻NO₂分子中的氮原子形成中间体1 (HOONO₂), 接着中间体1 (HOONO₂)经过氢转移形成产物P₂ (trans-HONO＋³O₂), 以上两个反应通道都是放热反应通道, 分别放热90.14和132.52 kJ•mol^－1.     

HO2自由基与NO2反应通道的理论研究

应用密度泛函理论DFT/B3LYP对HO₂＋NO₂反应进行了研究, 在B3LYP/6-311G^**和CCSD(T)/6-311G^**水平上计算了HO₂自由基与NO₂分子反应的单重态和三重态反应势能面, 计算结果表明, 单重态反应势能面中的直接氢抽提反应机理是此反应的主要反应通道, 即HO₂自由基的氢原子转移到NO₂分子的氮原子上形成产物P₁ (HNO₂＋³O₂), 另一个可能的反应通道是单重态反应势能面上HO₂中的端位氧原子进攻NO₂分子中的氮原子形成中间体1 (HOONO₂), 接着中间体1 (HOONO₂)经过氢转移形成产物P₂ (trans-HONO＋³O₂), 以上两个反应通道都是放热反应通道, 分别放热90.14和132.52 kJ•mol^－1.     

二元铜族团簇负离子催化CO氧化反应机理

用密度泛函理论B3LYP方法研究了二元铜族团簇负离子AuAg^-, AuCu^-和AgCu^-催化CO氧化反应的详细机理. 计算结果表明: CO在混合团簇中的吸附位顺序为Cu>Au>Ag; O₂也优先吸附到Cu上, 其次为Ag, 最难的为Au; 另外, O₂分子较CO分子易于吸附到混合团簇上. CO氧化反应有三条反应通道, 在热力学和动力学上均容易进行. AuAg-团簇催化CO氧化反应的最优反应通道为CO插入AuAgO₂^-中的Ag―O键形成中间体[Au―AgC(O―O)O]^-, 然后直接分解形成CO₂和AuAgO^-, 或另一个CO分子进攻中间体[Au―AgC(O―O)O]^-形成两分子的CO₂和AuAg^-. 而AuCu^-和AgCu^-催化CO氧化反应的最优反应通道为CO和O₂共吸附到团簇上,然后形成四元环中间体,最后四元环中间体分解形成产物或另一个CO分子进攻四元环中间体从而形成产物. 第二个CO分子的协同效应不明显. AuAg^-和AuCu^-对CO氧化反应催化活性强于Au₂^-团簇, 因此, Ag和Cu掺杂可以提高金团簇的催化活性, 与之前实验研究结果一致.     

CH2＝CClF hν >•CH＝CClF＋H光解反应的理论研究

采用UHF, CIS和CASSCF方法, 在aug-cc-pvdz基组水平上对CH₂＝CClF  ^hν >•CH＝CClF＋H的光解反应通道及其后续反应作了研究. 计算表明: 分子吸收一个光子后, 在第一电子激发态(S₁)经过一个过渡态解离与Cl原子同侧的C—H键, 这与用CIS方法计算垂直激发得到的π→σ^*_C—H跃迁及其对Frank-Condon点的计算中分子的单占轨道和键电荷密度变化所预测的结果是一致的. 光解产物•CH＝CClF(基态)还可再发生反应, 经过渡态解离C—Cl键或是C—F键.     

气相中Y＋, Zr＋, Nb＋与CO2反应的理论研究

以Y^＋, Zr^＋, Nb^＋与CO₂反应作为第二前过渡金属离子与CO₂反应的范例体系. 采用密度泛函UB3LYP方法, 对于Y, Zr, Nb采用Stuttgart赝势基组, 对于CO₂采用6-311＋G(2d)基组, 计算研究了三种金属离子在基态和激发态时与CO₂气相反应的机理. 结果表明三种金属离子与CO₂反应以高自旋进入反应通道, 在反应过程中发生系间窜越, 以低自旋中间体和最终产物离开反应通道. 用内禀坐标单点垂直激发计算的方法找到了势能面交叉点, 并作了相应的讨论. 因为有金属离子的参与, 使单分子CO₂的强吸热分解反应变为生成CO和MO^＋的放热过程.     

气相中Y＋, Zr＋, Nb＋与CO2反应的理论研究

以Y^＋, Zr^＋, Nb^＋与CO₂反应作为第二前过渡金属离子与CO₂反应的范例体系. 采用密度泛函UB3LYP方法, 对于Y, Zr, Nb采用Stuttgart赝势基组, 对于CO₂采用6-311＋G(2d)基组, 计算研究了三种金属离子在基态和激发态时与CO₂气相反应的机理. 结果表明三种金属离子与CO₂反应以高自旋进入反应通道, 在反应过程中发生系间窜越, 以低自旋中间体和最终产物离开反应通道. 用内禀坐标单点垂直激发计算的方法找到了势能面交叉点, 并作了相应的讨论. 因为有金属离子的参与, 使单分子CO₂的强吸热分解反应变为生成CO和MO^＋的放热过程.     

Cp4An和COT2An(Cp-=C5H5-,COT2-=C8H82-,An=U(IV),Pu(IV))的结构和光谱性质的密度泛函理论研究

采用密度泛函理论研究气相和四氢呋喃（THF）溶剂中Cp₄An和COT₂An（Cp^-=C₅H₅^-,COT^2-=C₈H₈^2-,An=U（IV）,Pu（IV））配合物的性质。THF溶剂对配合物的溶剂化效应采用类导体极化连续模型（CPCM）近似计算。计算结果显示在THF溶液中各配合物结合能的大小顺序为COT₂Pu > COT₂U > Cp₄Pu > Cp₄U。溶剂化效应降低了该金属有机配合物的结合能。计算得到的化合物的结构参数和红外光谱数据与实验数据保持一致。通过对Cp₄An和COT₂An（An=U（IV）,Pu（IV））的分子轨道能级图分析发现,采用最高的RSC ECP赝势计算COT₂U和Cp₄U的基态分别为三重f_φ²和f_σ²组态;而COT₂Pu和Cp₄Pu的基态分别为五重f_σ¹f_π¹f_φ¹和f_σ³f_δ¹组态。     

柚皮素、柚皮苷与溶菌酶相互作用的荧光光谱法研究

应用荧光光谱法研究了50%甲醇/水体系中柚皮素、柚皮苷与溶菌酶分子间的结合反应. 以Lineweaver-Burk双倒数方程和能量传递原理分别计算了两者与溶菌酶反应的结合常数(K)和结合距离(r): K_柚皮素^{25 ℃}＝4.00×10⁴, K_柚皮苷^{25 ℃}＝3.48×10⁴; r_柚皮素＝3.21 nm, r_柚皮苷＝3.30 nm, 以及由热力学参数的计算判断了两种分子与溶菌酶之间的作用力类型. 结果表明: 柚皮素、柚皮苷均能与溶菌酶以疏水作用相结合形成非共价化合物, 从而导致溶菌酶内在荧光的静态猝灭; 相对柚皮素, 柚皮苷与溶菌酶的结合距离增大, 作用强度减弱, 表明黄酮分子上多糖的取代不利于黄酮分子与蛋白之间的亲和作用. 根据Haslam等提出的多酚-蛋白质反应模型, 从分子水平初步探讨了糖取代对黄酮分子与蛋白相互作用减弱的原因.     

Cp4An和COT2An（Cp-=C5H5-，COT2-=C8H2-，An=U(Ⅳ)，Pu(Ⅳ)）的结构和光谱性质的密度泛函理论研究

采用密度泛函理论研究气相和四氢呋喃（THF）溶剂中Cp₄An和COT₂An（Cp^-=C₅H₅^-,COT^2-=C₈H^2-,An=U(Ⅳ),Pu(Ⅳ)）配合物的性质。THF溶剂对配合物的溶剂化效应采用类导体极化连续模型（CPCM）近似计算。计算结果显示在THF溶液中各配合物结合能的大小顺序为COT₂Pu > COT₂U > Cp₄Pu > Cp₄U。溶剂化效应降低了该金属有机配合物的结合能。计算得到的化合物的结构参数和红外光谱数据与实验数据保持一致。通过对Cp₄An和COT₂An（An=U(Ⅳ),Pu(Ⅳ)）的分子轨道能级图分析发现,采用最高的RSC-ECP赝势计算COT₂U和Cp₄U的基态分别为三重f_φ²和f_σ²组态;而COT₂Pu和Cp₄Pu的基态分别为五重f_σ¹f_π¹f_φ²和f_σ³f_δ¹组态。     

HCF(X~1A’)+SO2反应的动力学研究

用激光光解-激光诱导荧光方法研究了室温下(T＝293 K) HCF(X^~1A^’)自由基与SO₂分子的反应动力学. 实验中HCF(X^~1A^’)自由基是由213 nm激光光解HCFBr₂产生的, 用激光诱导荧光(LIF)检测HCF(X^~1A^’)自由基的相对浓度随着反应时间的变化, 得到此反应的二级反应速率常数为: k＝(1.81±0.15)×10^－12 cm³•molecule^－1•s^－1, 体系总压为1862 Pa. 高精度理论计算表明, HCF(X^~1A^’)和SO₂分子反应的机理是典型的加成-消除反应. 我们运用RRKM-TST理论计算了此二级反应速率常数的温度效应和压力效应, 计算结果和室温下测定的二级反应速率常数符合得较好.     

Synthesis, Structure, and Nonrigidity of Os7(CO)20(CNBu t )

The cluster Os₇(CO)₂₀(CNBu ^t ) (1) has been prepared in 25% yield by the reaction of Os₆(CO)₁₈ with Me₃NO and Os(CO)₄(CNBu ^t ) at –78°C. The crystal structure of 1 reveals the expected capped octahedral arrangement of metal atoms with the noncarbonyl ligand attached to the capping Os atom. The OsOs lengths in the two independent molecules in the unit cell are in the range 2.823(1)–2.922(1) Å, with the longer bonds associated with the Os₃ triangle farthest from the capping Os atom. The ¹³C NMR spectrum of 1 in solution at room temperature has a 3:3:1 pattern that is consistent with rotation of the individual Os(CO)₂(L) (L=CO or CNBu ^t ) groups in the cluster. This in turn supports the idea that the capping Os(CO)₂(CNBu ^t ) unit binds to the central Os₆ via a centrally directed MO plus two tangential molecular orbitals.     

Ab initio Quantum Mechanics/Molecular Mechanics Molecular Dynamics Simulation of CO in the Heme Distal Pocket of Myoglobin

Myoglobin has important biological functions in storing and transporting small diatomic molecules in human body. Two possible orientations of carbon monoxide (CO) in the heme distal pocket (named as B₁ and B₂ states) of myoglobin have been experimentally indicated. In this study, ab initio quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulation of CO in myoglobin was carried out to investigate the two possible B states. Our results demonstrate that the B₁ and B₂ states correspond to Fe…CO (with carbon atom closer to iron center of heme) and Fe…OC (with oxygen atom closer to Fe), by comparing with the experimental infrared spectrum. QM electrostatic polarization effect on CO brought from the protein and solvent environment is the main driving force, which anchors CO in two distinctive orientations and hinders its rotation. The calculated vibrational frequency shift between the state B₁ and B₂ is 13.1 cm^-1, which is in good agreement with experimental value of 11.5 cm^-1. This study also shows that the electric field produced by the solvent plays an important role in assisting protein functions by exerting directional electric field at the active site of the protein. From residue-based electric field decomposition, several residues were found to have most contributions to the total electric field at the CO center, including a few charged residues and three adjacent uncharged polar residues (namely, HIS64, ILE107, and PHE43). This study provides new physical insights on rational design of enzyme with higher electric field at the active site.     

The Silicon Carbonyls Revisited: On the Existence of a Planar Si(CO)4

Recently, some works have focused attention on the reactivity of silicon atom with closed-shell molecules. Silicon may form a few relatively stable compounds with CO, i.e. Si(CO), Si(CO)₂, Si[C₂O₂], while the existence of polycarbonyl (n>2) silicon complexes has been rejected by current literature. In this paper, the reaction of silicon with carbonyl has been reinvestigated by density functional calculations. It has been found that the tetracoordinated planar Si(CO)₄ complex is thermodynamically stable. In Si(CO), silicon carbonyl, and Si(CO)₂, silicon dicarbonyl, the CO are datively bonded to Si; Si(CO)₄, silicon tetracarbonyl, may be viewed as a resonance between the extreme configurations (CO)₂Si + 2CO and 2CO + Si(CO)₂; while Si[C₂O₂], c-silicodiketone, is similar to the compounds formed by silicon and ethylene. A detailed orbital analysis has shown that the Si bonding with two CO is consistent with the use of sp ²-hybridized orbitals on silicon, while the Si bonding with four CO is consistent with the use of sp ² d-hybridized orbitals on silicon, giving rise to a planar structure about Si.     

Synthesis and X-Ray Crystal Structures of Fe2Ru(CO)12−n (CNBu t ) n and FeRu2(CO)12−n (CNBu t ) n (n=1, 2)

The clusters Fe₂Ru(CO)_12–n (CNBu ^t ) _n (3, n=1; 4, n=2), FeRu₂(CO)_12–n (CNBu ^t ) _n (5, n=1, 6, n=2) and FeRu₂(CO)₁₁(CNCy) (5a) have been prepared by direct substitution from the parent carbonyl precursors Fe₂Ru(CO)₁₂ (1) and FeRu₂(CO)₁₂ (2). All compounds have been characterized spectroscopically and clusters 3, 4, 5, and 6 by single crystal X-ray determinations. In all cases, the isonitrile ligands adopt axial or pseudo-axial positions on a ruthenium atom. The structures of 3–5 are very similar to their parent clusters, but the extent of metal framework disorder is significantly less. Cluster 6 adopts the same C _2v Fe₃(CO)₁₂ type structure as 4, and thus differs markedly from the parent compound 2, which has a D ₃ structure .     

Backbonding in Thorium(IV) and Uranium(IV) Diarsenido Complexes with tBuNC and CO

The coordination of tBuNC and CO with the diarsenido complexes (C₅Me₅)₂An(η²-As₂Mes₂), An=Th, U, has been investigated. For the first time, a comparison between isostructural complexes of Th^IV and U^IV has been possible with CO; density functional calculations indicated an appreciable amount of π backbonding that originates from charge transfer from an actinide-arsenic sigma bond. The calculated CO stretching frequencies in the Th^IV and U^IV diarsenido complexes are consistent with the experimental measurements, both show large shifts to lower frequency. We demonstrate that the π backbonding is crucial to explaining the red shifts of CO frequency upon An^IV complex formation. Interestingly, this interaction essentially correlates to the parallel orientation of π*(C−O) orbitals relative to the An−As bond.     

Theoretical investigation on the reaction of N2O and CO catalyzed by Fe(C6H6)

The reaction of N₂O with CO, catalyzed by Fe⁺(C₆H₆) and producing N₂ and CO₂, has been investigated at the UB3LYP/6-311+G(d) level. The computation results revealed that the reaction of Fe⁺(C₆H₆), N₂O and CO, is an O-atom abstraction mechanism. For the reaction channels, the geometries and the vibrational frequencies of all species have been calculated and the frequency modes analysis also have been given to elucidate the reaction mechanism. On the basis for geometry optimizations, the thermodynamic data of these reactions channels have been calculated using the statistical theory at 295.15 K and pressure of 0.35 Torr. Using Eyring transition state theory with Wigner correction, the activation thermodynamic data, rate constant and frequency factors for the these reaction channels also have been given. The results showed that CO and N₂O do not react without catalyst and Fe⁺(C₆H₆) can excellently mediate the reaction of N₂O and CO.     

Reaction of metal carbonyls with 2-hydroxy-1-naphthaldeyde methanesulfonylhydrazone and characterization of the substitution products

Five new complexes, [M(CO)₅(nafmsh)] [M?=?Cr, 1; Mo, 2; W, 3], [Re(CO)₄Br(nafmsh)], 4 and [Mn(CO)₃(nafmsh)], 5 have been synthesized by the photochemical reaction of metal carbonyls [M(CO)₆] (M?=?Cr, Mo, W), [Re(CO)₅Br], and [Mn(CO)₃Cp] with 2-hydroxy-1-naphthaldehyde methanesulfonylhydrazone (nafmsh). The complexes have been characterized by elemental analysis, EI mass spectrometry, FT-IR, and ¹H NMR spectroscopy. The spectroscopic studies show nafmsh is a monodentate ligand coordinating via the imine N donor atom in 1–4 and as a tridentate ligand in 5.     

Synthesis and Characterization of the products from reaction of Metal Carbonyls [M(CO)6 (M Cr,Mo, W), Re(CO)5Br,Mn(CO)3Cp] with Salicylaldehyde Methanesulfonylhydrazone

Five new complexes, [M(CO)₅(salmsh)] (M?=?Cr;?1,?Mo;?2,?W;?3), [Re(CO)₄Br(salmsh)], 4, and [Mn(CO)₃ (salmsh)], 5, have been synthesized by the photochemical reaction of metal carbonyls with salicylaldehyde methanesulfonylhydrazone (salmsh). The complexes have been characterized by elemental analyses, EI mass spectrometry, FT-IR and ¹H NMR spectroscopy. The spectroscopic studies show that salmsh behaves as a monodentate ligand coordinating via the imine N donor atom in 1–4 and as a tridentate ligand in 5.     

Theoretical study on the reaction mechanism of NO and CO catalyzed by Rh atom

The gas-phase reaction mechanism of NO and CO catalyzed by Rh atom has been systematically investigated on the ground and first excited states at CCSD(T)//B3LYP/6-311+G(2d), SDD level. This reaction is mainly divided into two reaction stages, NO deoxygenation to generate N₂O and then the deoxygenation of N₂O with CO to form N₂ and CO₂. The crucial reaction step deals with the NO deoxygenation to generate N₂O catalyzed by Rh atom, in which the self-deoxygenation of NO reaction pathway is kinetically more preferable than that in the presence of CO. The minimal energy reaction pathway includes the rate-determining step about N–N bond formation. Once the NO deoxygenation with CO catalyzed by rhodium atom takes place, the reaction results in the intermediate RhN. Then, the reaction of RhN with CO is kinetically more favorable than that with NO, while both of them are thermodynamically preferable. These results can qualitatively explain the experimental finding of N₂O, NCO, and CN species in the NO + CO reaction. For the N₂O deoxygenation with CO catalyzed by rhodium atom, the reaction goes facilely forward, which involves the rate-determining step concerning CO₂ formation. CO plays a dominating role in the RhO reduction to regenerate Rh atom. The complexes, OCRhNO, RhON₂, RhNNO, ORhN₂, RhCO₂, RhNCO, and ORhCN, are thermodynamically preferred. Rh atom possesses stronger capability for the N₂O deoxygenation than Rh⁺ cation.     

Chemistry of vinylidene complexes

The reaction of Cp(CO)₂Mn=C=CHPh(1) with Pd(PPh₃)₄ followed by the replacement of the PPh₃ ligands by diphosphines Ph₂P(CH₂)₂PPh₂ (dppe) or Ph₂P(CH₂)₃PPh₂ (dppp) (where dppe is bis(diphenylphosphino)ethane and dppp is 1,3-bis(diphenylphosphino)propane) afforded the binuclear complexes Cp(CO)₂MnPd(μ-C=CHPh)(dppe) (2a) and Cp(CO)₂MnPd(μ-C=CHPh)(dppp) (2b), respectively. The reactions of2a and2b with Fe₂(CO)₉ gave the trinuclear complex CpMnFe₂(μ₃-C=CHPh(CO)₃ (3). Competitive transmetallation took the second pathway to yield clusters containing the PdFe₃ and PdFe₂ cores. Complex3 was also formed in the thermal reaction of compound1 with Fe₂(CO)₉. Complex3 was studied by IR spectroscopy,¹H and¹³C NMR spectroscopy, mass-spectrometry, and X-ray diffraction analysis. For Part 14, see Ref. 1. In this country, the chemistry of vinylidene complexes originated at the laboratory headed by K. N. Anisimov with the encouragement and active assistance of A. N. Nesmeyanov. At this laboratory, the acetylene-vinylidene rearrangement, which is presently a general procedure for the synthesis of vinylidene complexes of Groups IV–X transition metals, has been discovered, the ability of the metallaallenic M=C=C system to add the second metal atom has been found, and heterometallic μ-vinylidene complexes have been prepared for the first time. The development of this field of chemistry would be impossible without stimulating interest in vinylidene compounds expressed by Yu. T. Struchkov. At the laboratory headed by him, the structures of new complexes have been unambiguously established, and these investigations are being continued. The chemistry of vinylidene complexes has been further developed at the laboratory headed by A. A. Ioganson at the Krasnoyarsk Institute of Chemistry. The present work was dedicated to the blessed memory of these outstanding scientists. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 523–529, March, 2000.