Density Functional Theory Study on the Nitration of Halobenzene by Nitronium Ion

The rate determining steps of isomeric ortho, meta and para nitrations of fluorobenzene and chlorobenzene have been theoretically investigated at the B3LYP/6‐311G* level. Stationary points of the step involving reactant, transition state and intermediate complexes were successfully located and characterized without any restriction on the internal coordinates. Their molecular geometries, electronic structures, IR spectra, and the FMO symmetries of two initial aromatic compounds and the NO₂⁺ suggest that the halogens are ortho‐para directive, and also activating substituents in the gas phase. The blue shift of the C‐N stretching vibration and the red shift of the tetrahedral C‐H stretching vibration from transition state to Wheland intermediate demonstrate that the formation of the C‐N and the cleavage of the C‐H are not concerted but stepwise at the rate determining step. This provides theoretical evidence for the experimental fact of the absence of primary kinetic isotopic effect in most aromatic nitration reactions. The fully optimized geometries of nitro‐chlorobenzene complexes show that the C‐Cl bond in nitro‐chlorobenzene complexes become much shorter than in chlorobenzene molecules and appears as a double bond. On the contrary, the C‐F bond in nitro‐fluorobenzene complexes is still a single bond, and even lengthens slightly as the NO₂⁺ moves toward the fluorobenzene. This reveals that there is a special interaction, namely inductomeric effect, between the chlorine and nitro group in nitro‐chlorobenzene complexes. The inductomeric effect may cause a marked increase in the percentage of ortho product for the nitration of chlorobenzene.     

Ion size influence on the Ar solvation shells of M(+)-C6F6 clusters (M = Na, K, Rb, Cs)

The size-specific influence of alkali metal ions in the gradual transition from cluster rearrangement to solvation dynamics is investigated by means of molecular dynamics simulations for alkali metal cation-hexafluorobenzene systems, M(+)-C(6)F(6) (M = Na, K, Rb and Cs), surrounded by Ar atoms. To analyze such transition, different small aggregates of the M(+)-C(6)F(6)-Ar(n) (n = 1, ..., 30) type and M(+)-C(6)F(6) clusters solvated by about 500 Ar atoms are considered. The Ar-C(6)F(6) interaction contribution has been described using two different formalisms, based on the interaction decomposition in atom-bond and in atom-effective atom terms, which have been applied to study the small aggregates and to investigate the Ar solvated M(+)-C(6)F(6) clusters, respectively. The selectivity of the promoted phenomena from the M(+) ion size and their dependence from the number of Ar atoms is characterized.     

密度泛函理论和从头算方法对四唑负离子的比较研究

运用多种密度泛函理论(DFT)方法和从头算(abinitio)方法研究了四唑负离子的分子几何、电子结构、红外光谱和热力学性质.结果表明,B3LYP-DFT法与MP2-abinitio法计算结果较吻合,故可用于对四唑衍生物及其配合物的系统研究.     

C60-多吡啶Ru(II)配合物电子光谱的密度泛函理论研究

应用密度泛函理论(DFT)方法对两种C60-多吡啶Ru(II)衍生物进行理论研究. 在TZP全电子基组优化构型基础上, 通过分析前线轨道组成, 探讨金属及配体对C60母体影响; 以LB及SAOP校正局域密度近似, 用含时密度泛函(TDDFT)方法, 考虑溶剂化效应, 计算化合物1和2的电子吸收光谱. 结果表明, 化合物1和2在气相与丙酮溶液中所对应的光谱值差异较为明显, 溶剂化效应使吸收光谱蓝移. 计算得到化合物1和2在丙酮溶液中电子光谱与实验值吻合较好, 低能跃迁多为金属参与的混合跃迁, 高能跃迁主要由C60与配体部分贡献.     

HZSM-5分子筛上乙基叔丁基醚合成反应的理论研究

采用ONIOM (B3LYP/6-31G(d,p):UFF)分层计算的方法, 研究了HZSM-5 分子筛上乙醇和异丁烯合成乙基叔丁基醚(ETBE)的反应机理. 通过反应物在HZSM-5 分子筛上吸附性质的研究发现, 乙醇与分子筛酸性位相互作用形成氢键, 而异丁烯则作用在Brönsted 酸位上形成π配位吸附. 确定反应物吸附位置后, 进一步探索反应机理, 结果表明: HZSM-5分子筛上乙醇和异丁烯合成乙基叔丁基醚的反应为协同反应, 并且, 反应物吸附顺序的不同对反应过程存在一定的影响. ETBE合成反应的最优途径以反应物同时吸附形成的复合物作为起点. 在反应过程中, 形成π配位的H原子向异丁烯分子中不饱和双键的端位C原子靠近, 被吸附的乙醇分子中的O原子向异丁烯双键中的另一个C原子靠近, 直到形成C－O键, 生成ETBE. 这一过程中, 原有的质子H加成到异丁烯的端基C上形成C－H键, 而原醇羟基中的H和B酸位附近的O原子作用形成新的酸性位. 相应的协同反应的最低的反应势垒为25.14 kJ·mol^-1.     

Na＋-丙氨酸二肽络合离子结构的密度泛函理论研究

运用密度泛函理论B3LYP方法在6-311＋＋G**基组水平下研究了Na^＋与丙氨酸二肽(AD)分子结合形成的6种Na^＋-AD 络合离子, 其中包括2种双齿结构和4种单齿结构. 考察了6种Na^＋-AD络合离子的相对稳定性, 分析了丙氨酸二肽分子与Na^＋作用过程中分子骨架Ramachandran角f和Ψ以及分子内氢键的变化.     

基于密度泛函理论研究锂-冠醚复合物的结构和热力学参数

冠醚对碱金属离子具有高选择性,在锂元素的分离富集上有着广泛的应用。本文基于密度泛函理论（DFT）研究了冠醚环大小、取代基种类、配位原子种类和数量等因素对冠醚空间结构和热力学参数的影响。结果表明,苯并冠醚系列中的苯并-15-冠-5具有更好的配位能力,取代基、配位原子对冠醚的络合能力均有一定影响,因此可通过选择合适的冠醚环,引入供电子基团和含氮杂原子等方法来改善冠醚的分离富集能力。这对冠醚体系分离富集锂元素具有重要的指导意义。     

Theoretical Investigation on the Origin of Yellow‐Green Firefly Bioluminescence by Time‐Dependent Density Functional Theory

The question whether the emitter of yellow‐green firefly bioluminescence is the enol or keto‐constrained form of oxyluciferin (OxyLH₂) still has no definitive answer from experiment or theory. In this study, Arg220, His247, adenosine monophosphate (AMP), Water324, Phe249, Gly343, and Ser349, which make the dominant contributions to color tuning of the fluorescence, are selected to simulate the luciferase (Luc) environment and thus elucidate the origin of firefly bioluminescence. Their respective and compositive effects on OxyLH₂ are considered and the electronic absorption and emission spectra are investigated with B3LYP, B3PW91, and PBE1KCIS methods. Comparing the respective effects in the gas and aqueous phases revealed that the emission transition is prohibited in the gas phase but allowed in the aqueous phase. For the compositive effects, the optimized geometry shows that OxyLH₂ exists in the keto(?1) form when Arg220, His247, AMP, Water324, Phe249, Gly343, and Ser349 are all included in the model. Furthermore, the emission maximum wavelength of keto(?1)+Arg+His+AMP+H₂O+Phe+Gly+Ser is close to the experimental value (560 nm). We conclude that the keto(?1) form of OxyLH₂ is a possible emitter which can produce yellow‐green bioluminescence because of the compositive effects of Arg220, His247, AMP, Water324, Phe249, Gly343, and Ser349 in the luciferase environment. Moreover, AMP may be involved in enolization of the keto(?1) form of OxyLH₂. Water324 is indispensable with respect to the environmental factors around luciferin (LH₂).     

Theoretical Analysis of the Heterocyclic [4+2] Cycloaddition Between Pyridinium Ion and Enol Ether

Dearomative heterocyclic [4+2] cycloaddition between the N-(2,4-dinitrophenyl)pyridinium ion of nicotinamide and an enol ether was analyzed by Density Functional Theory (DFT) calculations. The calculation revealed that the reaction undergoes stepwise bond formation rather than occurring in a concerted manner. The experimental products were found to be both kinetically and thermodynamically favored. The calculated transition states and intermediate suggested that the high diastereoselectivity is derived from the electrostatic interaction between the 2-nitro group of the pyridinium ion and the hydrogen of the enol ether.     

Scalar Relativistic Density Functional Theoretical Investigation of Higher Complexation Ability of Substituted 1,10‐Phenanthroline over Bipyridine Towards Am3+/Eu3+ Ions

The better selectivity of Am³⁺ over Eu³⁺ ion with N‐based CyMe4‐BTPhen compared to CyMe4‐BTBP for experimentally observed [ML₂(NO₃)]²⁺ complexes was demonstrated using scalar relativistic DFT in conjunction with Born‐Haber thermodynamic cycle and COSMO solvation model. The calculated free energy of extraction, ΔG_ext reveals strong dependence on the hydration free energies of Am³⁺ and Eu³⁺ ions and week dependence to the difference in Gibbs free energy of solvation of the ligand or metal‐ligand complexes. Further, for the first time, we have computed the effect of co‐anion species ([M(NO₃)₅]^2–) on ΔG_ext of Am³⁺ and Eu³⁺ ions with CyMe4‐BTPhen and CyMe4‐BTBP, which adds a positive contribution and thus reduces the ΔG_ext. The calculated values of ΔΔΔG_ext (= ΔΔG_ext,L1 – ΔΔG_ext,L2, ΔΔG_ext = ΔG_ext,M1 – ΔG_ext,M2) can be used to avoid the very sensitive metal ion solvation energy, effect of co‐anionic species and thus provides a robust approach to determine the selectivity between two metal ions towards different competitive ligands. The natural population analysis (NPA), molecular orbital analysis, Mayer bond order analysis, and bond character analysis using Bader's quantum theory of atoms in molecules indicates slightly more covalency for complexes of Am³⁺ ion that are correlated to the experiental selectvity of Am³⁺ ion over Eu³⁺ ion and hence might be useful in the design and development of next generation extractants.     

Density Functional Theoretical Study on the Reaction Mechanism of HOCO and Its Radical

In this paper, the reaction mechanism of HOCO with its radical has been investigated deeply by density functional theory(DFT), while the geometries and harmonic vibration frequencies of the reactants, intermediates, transition states and products have been calculated at the B3LYP/6-311++G** level. The CCSD(T)/cc-p VQZ method was used to further calculate the single-point energy of each stationary point along the reaction channel. The result shows that channels(b) and(d) via carbon-carbon intermediates are competing with the ones(e),(f),(i) and(l) through carbon-oxygen intermediates, and the six channels are dominant for the title reaction to produce HCOOH and CO2. The result also indicates that the hydrogen abstraction from the HOCO radical can be performed quickly by the self-interaction of HOCO in the absence of other radicals or atoms, which indirectly proves for the first time that the ground-state cis-HOCO radical is not decomposed by the tunneling effect. In addition, the charges of natural population analysis(NPA) and the variation of chemical bonds have been analyzed by the Natural Bond Orbital(NBO) method along with the important reaction path.     

密度泛函理论方法研究锂离子电池电解液体系分子-离子结构

采用密度泛函理论方法,研究锂离子电池碳酸丙烯酯（PC）基电解液体系中锂盐离子与溶剂分子静电相互作用形成的可能结构. 计算结果表明,电解液中溶剂分子-离子的结构取决于体系的溶剂分子数. 在PC基电解液,Li⁺最多只能与4个PC溶剂分子相结合,锂盐阴离子与带正电的PC分子烷基基团相结合,而不以自由离子形式存在. 本文的计算结果能很好地解释文献报道的实验结果.     

HNO与O自由基反应的密度泛函理论研究

用密度泛函理论(DFT)和从头算方法，对HNO与O自由基反应进行了研究。在(U)B3LYP/6-311G^**和(U)B3LYP/aug-cc-pVTZ水平下优化了反应通道上各驻点(反应物、中间体、过渡态及产物)的几何构型。在(U)QCISD/aug-cc-pVTZ水平下计算了各物种的单点能，并对总能量进行了零点能校正。研究结果表明，HNO与O自由基反应过程中存在O → N、O → O和O → H进攻的竞争机制，且存在着多条反应通道。采用过渡态理论计算了600～2 000 K温度范围内3条慢反应通道的速率常数。求得lnk和1/T之间的线性关系。3种通道的阿累尼乌斯指前因子分别为1.469 × 10¹⁰、1.22 × 10¹⁰(1.06 × 10¹⁰)和2.26 × 10¹³。     

三氟化氯和水反应的密度泛函理论研究

应用量子化学密度泛函理论(DFT), 对ClF3和H2O在不同比例下的反应进行了研究. 在B3pw91/6-31++G(d,p)水平上优化了反应物、中间体、过渡态和产物的几何构型, 计算出它们的振动频率和零点振动能(ZPVE), 并对能量进行了校正. 计算结果表明, ClF3和H2O的反应能垒很低, 反应极易进行;水足量有利于生成HClO2, 少量有利于生成其它卤氧化合物.     

乙炔基自由基C2H与氧气反应的密度泛函理论研究

应用量子化学从头算和密度泛函理论(DFT)对C₂H自由基和O₂的反应进行了研究.在B3LYP/6-311G^**水平上优化了反应通道上各驻点(反应物、中间体、过渡态和产物)的几何构型,并计算出它们的振动频率和零点振动能(ZPVE).各物种的总能量由CCSD(T)/6-311G^**//B3LYP/6-311G^**给出,并对能量进行了零点能校正.计算结果表明,反应物中自由基C₂H中的边端C进攻O₂形成了中间体1 (HCCOO),中间体1是一个加合产物.由中间体1经过不同的反应通道可以生成不同的产物P₁ (HCO+CO), P₂ (HCCO+O), P₃(CO₂+CH), P₄ (C₂O+OH)和P₅ (2CO+H).反应通道之间存在着竞争机制.其中P₁, P₂是主要产物,其次还有一定比例的P5生成,而产物P₃, P₄的生成几率较低.各条反应通道化学反应热的计算与实验吻合较好.     

三氟化硼和水反应的密度泛函理论研究

应用密度泛函理论对三氟化硼和水的反应进行了研究. 在 B3PW91/6-31＋＋G(d,p)水平上优化了各驻点(反应物, 中间体, 过渡态和产物)的几何构型, 并计算了它们的振动频率和零点振动能, 并对能量进行了校正. 计算结果表明, 三氟化硼和水的反应比较复杂, 产物除氟化氢外, 还有硼酸, 氟硼酸, 硼氟氧酸等.     

Na-呋喃荷移络合物弱相互作用的密度泛函理论研究

在B3LYP/6-311+C*水平上,对Na-呋喃体系可能存在的弱相互作用复合物进行了全自由度能量梯度优化,发现了Na-呋喃体系存在两个能量极小结构A、B,其中,结构A是Na原子的3s1电子直接和呋喃杂环体系中的所有重原子的共轭大π体系相互偶合,形成一个具有C8对称性的金属有机复合物;而结构B为Na原子的3s1电子主要通过杂原子O和杂环上原有的五中心六电子大π体系形成一个新的平面六中心七电子大π体系,具有C2v对称性.结构B较结构A稳定3.40kJ/mol.结构A中的Na-O键长为0.38 nm,∠COC为106.9°,由于金属Na对呋喃杂环的作用使整个分子平面变形,C1、C2、C3、C4在同一个平面内,而O5则稍微翘离平面且O5原子距离由Cl、C2、C3、C4组成的平面的垂直距离约为0.035 nm.结构B中Na-O键长为0.26 nm,∠COC为106.8°,金属Na原子和杂环中所有的原子在同一个平面内.并在MP2和B3LYP水平下,用6-311+G*基组精确计算了最稳定结构B的结合能为ΔE=4.5～5.1 kJ/mol.     

Na-噻吩荷移配合物弱相互作用的理论研究

利用 B3LYP法在 6-31 1 +G* 水平上研究了 Na-噻吩体系可能存在的 3种 Na-噻吩复合物 A,B和 C分子结构 .结果表明 :Na-噻吩体系存在 2个能量极小结构 A和 C;结构 B未得到证实 .结构 A中 ,Na的 3s1电子直接和噻吩杂环的所有重原子进行弱相互作用形成一个具有 Cs对称性的金属有机复合物 ;结构 C中 ,Na原子的 3s1电子主要通过和与 S原子不直接相连的 C2和 C3进行弱相互作用 ,因而在原有的大 π键基础上形成一个新的大 π键 ,其结构为 C2 v对称性 .结构 A较结构 C稳定 78.0 k J/ mol.结构 A中的 Na—S之间的距离为 0 .4 0 7nm,键角∠ CSC为 91°,金属 Na和噻吩之间的弱相互作用使整个噻吩分子平面稍微变形 ,S原子向 Na所在的一侧稍微偏离 C环平面 .结构 C中 Na-S之间的距离为 0 .82 5 nm,∠ CSC为 91°,金属 Na原子和杂环中所有的原子在同一个平面内 .在 B3LYP、 MP2、 MP3和 MP4水平上 ,分别用 6-31 1 +G* 和 6-31 1 ++G* * 基组精确计算了最稳定结构 A的结合能 ΔE为 8.3～ 1 0 .9k J/ mo