Hartree–Fock and density functional theory study of remote substituent effects on heterolytic Fe–N bond energies of p‐G‐C6H4NHFe(CO)2(η5‐C5H5) and p‐G‐C6H4N(COMe)Fe(CO)2(η5‐C5H5)

The nature and strength of metal–ligand bonds in organotransition‐metal complexes are crucial to the understanding of organometallic reactions and catalysis. Quantum chemical calculations at different levels of theory have been used to investigate heterolytic Fe–N bond energies of para‐substituted anilinyldicarbonyl(η⁵‐cyclopentadienyl)iron [p‐G‐C₆H₄NH(η⁵‐C₅H₅)Fe(CO)₂, abbreviated as p‐G‐C₆H₄NHFp (1), where G = NO₂, CN, COMe, CO₂Me, CF₃, Br, Cl, F, H, Me, MeO, and NMe₂] and para‐substituted α‐acetylanilinyldicarbonyl(η⁵‐cyclopentadienyl)iron [p‐G‐C₆H₄N(COMe)(η⁵‐C₅H₅)Fe(CO)₂, abbreviated as p‐G‐C₆H₄N(COMe)Fp (2)] complexes. The results show that BP86 and TPSSTPSS can provide the best price/performance ratio and more accurate predictions in the study of ΔH_het(Fe–N)'s. The linear correlations [r = 0.98 (g, 1a), 0.93 (g, 2b)] between the substituent effects of heterolytic Fe–N bond energies [ΔΔH_het(Fe–N)'s] of series 1 and 2 and the differences of acidic dissociation constants (ΔpK_a) of N–H bonds of p‐G‐C₆H₄NH₂ and p‐G‐C₆H₄NH(COMe) imply that the governing structural factors for these bond scissions are similar. And the linear correlations [r = ?0.99 (g, 1c), ?0.92 (g, 2d)] between ΔΔH_het(Fe–N)'s and the substituent σ_p^? constants show that these correlations are in accordance with Hammett linear free energy relationships. The polar effects of these substituents and the basis set effects influence the accuracy of ΔH_het(Fe–N)'s. ΔΔH_het(Fe–N)'s(1, 2) follow the captodative principle. ME_{α‐COMe, para‐G}s include the influences of the whole molecules. The correlation of ME_{α‐COMe, para‐G}s with σ_p^? is excellent. ME_{α‐COMe, para‐G}s rather than ΔΔH_het(Fe–N)'s in series 2 are more suitable indexes for the overall substituent effects on ΔH_het(Fe–N)'s(2). Insight from this work may help the design of more effective catalytic processes. Copyright © 2012 John Wiley & Sons, Ltd.     

Formation mechanism of ethanol-water excimer

The fluorescent spectrum and the excitation spectrum were used to present the cluster molecular structure feature in ethanol-water solutions.Through analyzing the fluorescent characteristics of an excimer,it is proposed that the excimers are formed between the ethanol-water cluster molecules in the excited state and in the ground state.The fluorescent lifetime and the fluorescent intensity decay process give information about the photo-physical and photo-chemical processes of the formation and the dissociation of an excimer.The theoretical calculation and physical analysis coincide with the experimental results.The preliminary conclusion about the structure feature of ethanol-water cluster molecule is that it has a planar one like a sandwich.     

Substituent effects on gas‐phase homolytic Fe–N bond energies of m‐G‐C6H4NHFe(CO)2(η5‐C5H5) and m‐G‐C6H4N(COMe)Fe(CO)2(η5‐C5H5) studied using density functional theory methods

One of the most fundamental properties in chemistry is the bond dissociation energy, the energy required to break a specific bond of a molecule. In this paper, the Fe–N homolytic bond dissociation energies [ΔH_homo(Fe–N)'s] of 2 series of (meta‐substituted anilinyl)dicarbonyl(η⁵‐cyclopentadienyl) iron [m‐G‐C₆H₄NHFp ( 1 )] and (meta‐substituted α‐acetylanilinyl)dicarbonyl(η⁵‐cyclopentadienyl) iron [m‐G‐C₆H₄N(COMe)Fp ( 2 )] were studied using density functional theory methods with large basis sets. In this study, Fp is (η⁵‐C₅H₅)Fe(CO)₂, and G is NO₂, CN, COMe, CO₂Me, CF₃, Br, Cl, F, H, Me, MeO, and NMe₂. The results show that Tao‐Perdew‐Staroverov‐Scuseria, Minnesota 2006, and Becke's power‐series ansatz from 1997 with dispersion corrections functionals can provide the best price/performance ratio and accurate predictions of ΔH_homo(Fe–N)'s. The ΔΔH_homo(Fe–N)'s ( 1 and 2 ) conform to the captodative principle. The polar effects of the meta‐substituents show the dominant role to the magnitudes of ΔΔH_homo(Fe–N)'s. σ_α· and σ_c· values for meta‐substituents are all related to polar effects. Spin‐delocalization effects of the meta‐substituents in ΔΔH_homo(Fe–N)'s are small but not necessarily zero. RE plays an important role in determining the net substituent effects on ΔH_homo(Fe–N)'s. Insight from this work may help the design of more effective catalytic processes.     

Na2分子部分电子态的完全振动能谱和离解能的精确研究

对于大多数双原子分子的电子态，用现代实验方法或精确的量子理论方法往往可以获得含m个振动能级的能谱子集合［Ev］，而不易得到包含最高振动能级在内的所有高振动量子态能级的完全振动能谱{Ev}.鉴于Na2分子电子态的振动能谱和分子离解能De在实际研究和应用中的重要性，使用基于微扰理论的代数方法（AM），获得了Na2分子一些电子态的振动光谱常数和完全振动能谱；使用基于AM的代数能量方法（AEM）获得了这些电子态的正确离解能.研究结果表明：AM方法能从少数精确的实验能级获得精确的分子振动光谱常数集合和正确的完全振动能谱{Ev}，AEM方法获得的分子离解能比由文献发表的振动光谱常数计算得到的近似离解能值更准确，对于难以获得分子离解能的那些电子激发态，AEM方法能给出合理的离解能数据. 关键词： Na2分子 代数方法 振动能级 离解能 电子激发态     

基于反应力场的分子动力学方法研究氢在钯表面的分解

基于二阶矩近似反应力场方法构建的全维度势能面研究了氢分子及其同位素分子在钯表面的分解过程.在构建势能面的过程中数据库中只包含了氢分子与钯（111）表面相互作用的相关信息,该势能面在研究氢分子在钯（100）表面上的分解过程中表现出了非常好的可转移性.结果表明,氢分子及其同位素分子在钯（111）与钯（100）表面上的分解系数S₀均随着入射能量的增加呈现非单调变化,并且通过固定分子取向的方法发现同核分子（H₂、D₂和T₂）最有利分解取向角为90°,而异核分子（HD、HT和DT）受质心偏移的影响,其最有利分解取向角向大角度偏移.     

两种烷基碘化物分子C—I键解离的从头计算

分别采用多组态自洽场方法和二阶多组态准简并微扰论方法,计算了烷基碘化物分子CF₃I和C₂H₂F₃I沿C—I键的绝热势能曲线和垂直激发能. 结果发现,这两种分子的低激发态均为排斥态;基态的解离能分别为2.473eV和2.835eV,其中前者与实验结果符合较好. 关键词： 烷基碘化物分子 解离能 势能曲线     

Energetic and structural characterization of 2‐R‐3‐methylquinoxaline‐1,4‐dioxides (R = benzoyl or tert‐butoxycarbonyl): experimental and computational studies

The gaseous standard molar enthalpies of formation of two 2‐R‐3‐methylquinoxaline‐1,4‐dioxides (R = benzoyl or tert‐butoxycarbonyl), at T = 298.15 K, were derived using the values for the enthalpies of formation of the compounds in the condensed phase, measured by static bomb combustion calorimetry, and for the enthalpies of sublimation, measured by Knudsen effusion, using a quartz crystal oscillator. The three dimensional structure of 2‐tert‐butoxycarbonyl‐3‐methylquinoxaline‐1,4‐dioxide has been obtained by X‐ray crystallography showing that the two N? O bond lengths in this compound are identical. The experimentally determined geometry in the crystal is similar to that obtained in the gas‐phase after computations performed at the B3LYP/6‐311 + G(2d,2p) level of theory. The experimental and computational results reported allow to extend the discussion about the influence of the molecular structure on the dissociation enthalpy of the N? O bonds for quinoxaline 1,4‐dioxide derivatives. As found previously, similar N? O bond lengths in quinoxaline‐1,4‐dioxide compounds are not linked with N? O bonds having the same strength. Copyright © 2007 John Wiley & Sons, Ltd.     

Adsorption and reactions of ethanol on Mo2C/Mo(1 0 0)

The adsorption, desorption and dissociation of ethanol have been investigated by work function, thermal desorption (TPD) and high resolution electron energy loss (HREELS) spectroscopic measurements on Mo₂C/Mo(1 0 0). Adsorption of ethanol on this sample at 100 K led to a work function decrease suggesting that the adsorbed layer has a positive outward dipole moment By means of TPD we distinguished three adsorption states, condensed layer with a Tp = 162 K, chemisorbed ethanol with Tp = 346 K and irreversibly bonded species which decomposes to different compounds. These are hydrogen, acetaldehyde, methane, ethylene and CO. From the comparison of the Tp values with those obtained following their adsorption on Mo₂C it was inferred that the desorption of methane and ethylene is reaction limited, while that of hydrogen is desorption limited process. HREEL spectra obtained at 100 K indicated that at lower exposure ethanol undergoes dissociation to give ethoxy species, whereas at high exposure molecularly adsorbed ethanol also exists on the surface. Analysis of the spectral changes in HREELS observed for annealed surface assisted to ascertain the reaction pathways of the decomposition of adsorbed ethanol.     

355 nm激光作用下苯甲醚的多光子电离质谱研究

在355 nm激光作用下,利用多光子电离技术结合飞行时间质谱(TOF-MS)对苯甲醚分子进行了研究。实验结果表明苯甲醚分子的多光子电离机制属于母体分子电离-解离模型。通过对主要碎片离子的可能形成过程的讨论,得出该波长下母体分子离子解离的主要有两种通道,但是随激光能量的增强,甲基移除通道逐步占据优势成为主要通道。应用高斯软件采用HF/6-31G(d) 方法对苯甲醚分子和苯甲醚阳离子基态的几何构型进行优化得到其稳定构型,并计算了苯甲醚分子离子及其初级解离产物的能量。比较两条通道的碎片离子能量的变化,理论验证了实验中苯甲醚分子主要解离通道的合理性。     

Consequence for Wavefunction Collapse Model of the Sudbury Neutrino Observatory Experiment

It is shown that data on the dissociation rate of deuterium obtained in an experiment at the Sudbury Neutrino Observatory provides evidence that the Continuous Spontaneous Localization wavefunction collapse model should have mass–proportional coupling to be viable.