La+活化NH3的自旋禁阻反应机理

采用密度泛函理论的UB3LYP方法,计算研究了气相中La+活化NH3的两态反应机理。为了理解由La+活化NH3过程中自旋翻转行为,对自旋态分别为单重态和三重态两个反应势能面进行了计算研究,其结果表明,La+活化NH3的过程是通过自旋态势能面交叉产生的自旋禁阻反应,单、三重态势能面最低能量交叉点(MECP)附近的系间窜越导致H向La+转移和脱H2反应能垒的降低。此外,运用自然键轨道(NBO)布居分析,研究了反应中各个物种的成键特性。所确定的最低能量反应路径为:3La++NH3→3IM1→MECP→1TS12→1IM2→1TS23→1IM3→1LaNH++H2。     

气相中Ta~+活化分解CO_2的自旋禁阻反应机理

采用密度泛函理论中的UB3LYP方法,对Ta采用相对论校正赝势基组(SDD),C,O采用6-311+G(3d)基组,计算研究了气相中不同自旋态下Ta+活化CO2分解反应的微观机理.计算结果表明,Ta+活化CO2分解反应是典型的自旋禁阻反应,以五重态进入反应通道,经过五重态势能面到三重态势能面的系间窜越(ISC),最终产物TaO+,CO以三重态离开反应通道.运用Harvey方法优化出最低能量交叉点(MECP),并计算了MECP处的自旋-轨道耦合(SOC)常数(204.94cm-1),较大的SOC值说明了在MECP处的自旋-轨道耦合作用较强,势能面的交叉降低了自旋禁阻反应能垒,为反应提供了一条低能反应路径.运用Landau-Zener跃迁几率公式计算了MECP处系间窜越几率,较大的系间窜越几率说明了该自旋禁阻反应速率较快.     

气相中W+活化CO2分解的自旋禁阻反应机理

用密度泛函理论中的UB3LYP方法, 对W采用相对论校正赝势基组(SDD), 对C、O采用6-311+G(3d)基组, 研究了气相中不同自旋态W+活化CO2分解的反应机理. 计算结果表明, W+活化CO2分解反应以六重态进入反应通道, 经过六重态势能面到四重态势能面的系间窜越(ISC),最后产物WO+和CO以四重态离开反应通道. 运用Harvey方法优化出最低能量交叉点(MECP), 并计算了MECP处的自旋-轨道耦合(SOC)常数(494.95 cm-1), 势能面的交叉和在MECP处较强的自旋-轨道耦合作用降低了自旋禁阻反应能垒, 为反应提供了一条低能反应路径, 反应总放热量为122.33 kJ·mol-1.     

Ru催化N2与H2反应合成氨的两态反应机理

采用密度泛函理论(DFT)UB3LYP方法对Ru在单重态、三重态及五重态势能面上催化N_2与H_2反应合成氨的两态反应机理进行理论研究,发现该反应为典型的两态反应。计算得到最低能量交叉点(MECP)处自旋-轨道耦合常数(H_(soc))及双程系间窜越几率(P~(ISC)),MECP1:H_(soc)=508.34 cm~(-1),P_2~(ISC)=0.85,MECP9:H_(soc)=269.21 cm~(-1),P_2~(ISC)=0.27。运用能量跨度模型(energetic span model)确定Ru催化合成氨反应的转化频率(TOF)决速过渡态(TDTS)为~3TS2-3,TOF决速中间体(TDI)为~3IM9。     

气相中W~+活化CO_2分解的自旋禁阻反应机理

用密度泛函理论中的UB3LYP方法,对W采用相对论校正赝势基组(SDD),对C、O采用6-311+G(3d)基组,研究了气相中不同自旋态W+活化CO2分解的反应机理.计算结果表明,W+活化CO2分解反应以六重态进入反应通道,经过六重态势能面到四重态势能面的系间窜越(ISC),最后产物WO+和CO以四重态离开反应通道.运用Harvey方法优化出最低能量交叉点(MECP),并计算了MECP处的自旋-轨道耦合(SOC)常数(494.95cm-1),势能面的交叉和在MECP处较强的自旋-轨道耦合作用降低了自旋禁阻反应能垒,为反应提供了一条低能反应路径,反应总放热量为122.33kJ.mol-1.     

非血红素铁超氧化物活化丙烯分子多态反应机理的理论研究

采用密度泛函DFT-B3LYP理论对非血红素铁超氧化物活化丙烯分子多态反应机理进行了探讨.研究结果表明氢原子抽取过程遵守单态反应机制,主要在基态高自旋七重态势能面进行,且具有较低活化能（ΔG^≠=65.6 kJ·mol^-1）,非血红素铁超氧化物可以作为有效氧化剂抽取氢原子。单态反应机制可能归因于近来建议的交换-加强反应原则（EER,铁中心具有较大交换稳定作用）。对于O-O键的活化,在CASSCF（10,8）/6-31+G（d）//TZVP水平下,势能面交叉区内,高自旋七重态（S₁）和五重态（Q₀）的自旋-轨道耦合（SOC）常数分别为2.26和2.19 cm^-1。轨道分析表明两条发生翻转自旋轨道具有相同空间组成（π_sub^*）,SOC禁阻,因此通过SOC作用反应体系不可能有效地从七重态（S=3）势能面系间穿越到五重态（S=2）势能面,系间穿越可能发生在反应最后的退出阶段。     

非血红素铁超氧化物活化丙烯分子多态反应机理的理论研究

采用密度泛函DFT-B3LYP理论对非血红素铁超氧化物活化丙烯分子多态反应机理进行了探讨. 研究结果表明氢原子抽取过程遵守单态反应机制,主要在基态高自旋七重态势能面进行,且具有较低活化能（ΔG^≠=65.6 kJ·mol^-1）,非血红素铁超氧化物可以作为有效氧化剂抽取氢原子。单态反应机制可能归因于近来建议的交换-加强反应原则（EER,铁中心具有较大交换稳定作用）。对于O-O键的活化,在CASSCF（10,8）/6-31+G（d）//TZVP水平下,势能面交叉区内,高自旋七重态（S₁）和五重态（Q₀）的自旋-轨道耦合（SOC）常数分别为2.26和2.19 cm^-1。轨道分析表明两条发生翻转自旋轨道具有相同空间组成（π_sub^*）,SOC禁阻,因此通过SOC作用反应体系不可能有效地从七重态（S=3）势能面系间穿越到五重态（S=2）势能面,系间穿越可能发生在反应最后的退出阶段。     

气相VO（∑＋）与CH3OH（1^A′）分子自旋禁阻反应C—H，O—H键活化机理的理论研究

采用密度泛函理论（DFT）B3LYP与cCsD方法研究了二重态和四重态势能面自旋禁阻反应VO（∑’）活化cH30H（1^A′）分子c—H,0—H键的微观机理．通过自旋一轨道耦合的计算讨论了势能面交叉点和可能的自旋翻转过程．在MEcP处,四重态和二重态问的旋轨耦合常数为131．14cm^-1．自旋多重度发生改变,从四重态系间穿越到二重态势能面形成中间体2^IM1,导致反应势能面的势垒明显降低．     

气相中Cu+活化N2O中N-O键反应机理的理论研究

采用密度泛函UB3LYP/6 311+G(2d)方法计算研究了Cu+在基态和激发态下与N2O的反应机理,全参数优化了反应势能面上各驻点的几何构型,用频率分析方法和内禀反应坐标(IRC)方法对过渡态进行了验证,并用UCCSD(T)/6 311G(2d,p)、单点垂直激发、Harvey等人的方法分别进行各驻点单点能校正,单重态和三重态反应势能面交叉点CP确定,最低能量交叉点(MECP)的优化及MECP处相应的自旋 轨道耦合常数(SOC)计算。计算结果表明,该反应为一步反应,SOC值为84.2 cm-1,比较大的SOC值说明了在势能面上CP点处的翻转能够有效的降低反应的活化能,降低活化能值为27.6kJ.mol,增加反应放热126.7kJ.mol,这在动力学和热力学上对反应是非常有利。     

Ti^＋离子和C2H4分子自旋禁阻反应中C—H键活化机理的理论研究

用密度泛函B3LYP方法,研究了二重态和四重态势能面自旋禁阻反应Ti^＋（^4F,3d^24s^1）＋C2H4→TiC2H2^＋（^2A2）＋H2的微观机理．通过自旋．轨道耦合的计算讨论了势能面交叉点和可能的自旋翻转过程．中间体IM1-^4B2处,四重态和二重态间的旋-轨耦合值为59．3cm^-1．自旋多重度必将发生变化,从四重态系间穿越到二重态势能面形成共价型复合物IM1-^2A1,同时导致四重态势能面的势垒明显降低．到插入中间体IM2后,二重态势能面上有两条不同的反应路径,即分步和协同路径,后者在二重态势能面上得到放热产物TiC2H2^＋（^2A2）＋H2具有较低的活化势垒,4．52kcal／mol,其主反应路径为：Ti^＋＋C2H4→^4IC→IM1—^4B2→4.2ISC→IM1—^2A1→[^2TSins]→IM2-^2A”→[^2TSMCTS]→IM5→TiC2H2^＋（^2A2）＋H2．     

Monolith Manganese-Based Catalyst Supported on ZrO2-TiO2 for NH3-SCR Reaction at Low Temperature

Monolith catalysts were prepared using TiO₂ and ZrO₂-TiO₂ as supports with MnO₂ as active component and Fe₂O₃ as promoter. The catalytic activities at low temperature and stability at high temperature for selective catalytic reduction of NO_x with NH₃ (NH₃-SCR) in the presence of excessive O₂ were studied after the catalysts calcined at different temperatures. The catalysts were characterized by X-ray diffraction (XRD), specific surface area measurements (BET), oxygen storage capacity (OSC), and temperature programmed reduction (H₂-TPR). The results indicated that the catalyst supported on ZrO₂-TiO₂ had excellent stability at high temperature, and possessed high specific surface area and oxygen storage capacity, and had strong redox property. The results of the catalytic activities indicated that the monolith manganese-based catalyst using ZrO₂-TiO₂ as support had evidently improved the activity of NH₃-SCR reduction reaction at low temperature, and it showed great potential for practical application.     

NH0-1+2-3离解能等的高级ab initio计算与评价

A recent experimental determination[1] of the dissociation energies (D0) for H2N-H, H2N+-H and H2N-H+, the ionization energies for NH3 and NH2 resulted in large deviations when compared with those of the earlier values and the QCISD(T)/6-311+G(3df,2p) ab initio calculations. We have performed some higher level ab initio calculations on these data by utilizing the Gaussian 92/DFT and Gaussian 94 pakages of programs and have assessed the available experimental values. Our calculations were carried out at the QCISD (TQ)/aug-cc-pVDZ, G2(QCI), QCISD(T)/6-311 ++G(3df,3pd) and QCISD(T)/aug-cc-pVTZ levels of theory. Geometries were optimized at both of the MP2(full)/6-31G(d) and the MP2(full)/6-31(d,p) levels, and were compared with those of the experiments if available. The MP2(full)/6-31G(d,p) tight-optimized geometries for the neutrals are closer to those of the experiments than those of the MP2 (full)/6-31G(d), and are in excellent agreement with the experimental results as shown in Table 1. In this case, we assumed that the optimized geometries for the cations would be better if p polarization functions are added to the hydrogen atoms. We firstly noted that the symmetry of the NH3+ cation was D3h, other than Cs. as reported in ref.[1]. All of the zero-point energies and the final geometries are calculated at the MP2(full)/6-31G(d,p) level of theory. We have also repeated the QCISD(T )/6-311 + G(3df,2p) calculations of ref. [1], because we could not identify their level of goemetry optimization. It is found that the total energy, -55.244 19 Hartrees, for NH2+(1A1 ) in ref.[1] might be in error. Our result is -55.336 29 Hartrees at the same level of theory. At our highest level [QCISD(T)/aug-cc-pVTZ] of calculations as shown in Table 3, the D0 (temperature at zero Kelvin) values of H2N-H, H2N+-H(3B1for NH2+ ) and H2N- H+ are 4.51, 5.49 and 8.00 eV, respectively. These data reported in re f.[1] were 4.97, 5.59 and 8.41 eV, respectively. Our result on D0(H2N-H) supports the work of ref.[2,3,5,6]. The ionization energies (IE) for NH3 and NH2 (3B1 for NH2+) at our highest level are 10.11 and 11.09 eV while in ref.[1] were 10.16 and 10.78 eV, respectively. For the latter, our result supports the experiment of ref.[3]. Our predicted D0 for HN2+-H and IE for NH2 (1A1 for each NH2+) are 6.80 and 12.39 eV, respectively. These values differ greatly from the predicted values (9.29 and 14.88 eV) of ref.[1] where the total energy of NH2+(1A1) might be in error. The D0 value for HN-H has not been found in ref.[1]. Our result supports the work of ref.[3]. We have also derived all of these values at the temperature of 298K and under the pressure of 101kPa at several levels of thoery as shown in Table 3. On examining the experiment of ref.[1] in detail, it is easy to find that all of the larger deviations might be from a too high value of the appearance potential of proton AP(H+). Indeed, ref.[1] has mentioned that the determintion of AP(H+), due to kinetic shift, would lead to a hihger value for the dissociation energy as has been pointed out by Berkowitz and Ruscic. In this work, we concluded that, besides some mistakes in the theoretical calculations of ref.[1], the dissociation energies for H2N-H and H2N-H+,the IE for NH2 (3B1 for NH2+) might also be unreliable and need to be re-examined.
     

CrOx-CeO2二元氧化物表面NO的NH3催化还原反应机理

利用原位漫反射红外光谱法研究了473 K下在CrOx-CeO2二元氧化物表面NO的NH3催化还原反应的机理。研究了CrOx-CeO2二元氧化物表面在反应过程中的表面吸附物种。为了更加清晰的了解反应过程,在SCR反应过程中分别切断NH3和NO的气流,并采集了所生成的原位漫反射红外光谱图,通过研究以上结果得出结论:当前状态下的SCR反应过程可能服从ER机理。     

Spectroscopic properties of guanidinium zinc sulphate [C(NH2)3]2Zn(SO4)2 and ab initio calculations of [C(NH2)3]2 and HC(NH2)3

Raman and FTIR spectra of guanidinium zinc sulphate [C(NH₂)₃]₂Zn(SO₄)₂ are recorded and the spectral bands assignment is carried out in terms of the fundamental modes of vibration of the guanidinium cations and sulphate anions. The analysis of the spectrum reveals distorted SO₄²⁻ tetrahedra with distinct S–O bonds. The distortion of the sulphate tetrahedra is attributed to Zn–O–S–O–Zn bridging in the structure as well as hydrogen bonding. The CN₃ group is planar which is expressed in the twofold symmetry along the C–N (1) vector. Spectral studies also reveal the presence of hydrogen bonds in the sample. The vibrational frequencies of [C(NH₂)₃]₂ and HC(NH₂)₃ are computed using Gaussian 03 with HF/6-31G* as basis set.     

CrOx-CeO2二元氧化物表面NO的NH3催化还原反应机理

利用原位漫反射红外光谱法研究了473 K下在CrOx-CeO₂二元氧化物表面NO的NH₃催化还原反应的机理。研究了CrO-CeO₂二元氧化物表面在反应过程中的表面吸附物种。为了更加清晰的了解反应过程, 在SCR反应过程中分别切断NH₃和NO的气流, 并采集了所生成的原位漫反射红外光谱图, 通过研究以上结果得出结论:当前状态下的SCR反应过程可能服从E-R机理。     

NH_4Y_3F_(10)多孔纳米晶的制备及其在MALDI-TOF-MS中的应用(英文)

利用水热法合成出NH4Y3F10多孔纳米晶。由于Y3+离子的激发态能量可以转移给具有较高振动能的有机分子,因此这些多孔纳米晶可以作为基质辅助激光解析电离飞行时间质谱的基体材料,用于检测小分子和聚乙二醇。通过与商品化的基体材料(CHCA、DHB)对比,证明NH4Y3F10多孔纳米晶是一种性能优异的基体材料。这种新型基体材料已经成功应用于有机分子、小肽、C60、缺氧诱导因子(HIFs)和聚乙二醇的分子量的检测,显示出这种基体材料具有广泛的应用前景。