Hetero-nuclear MnNi+ cation exhibits high catalytic activity in the C–H bond activation of cyclohexane in comparison with mono-nuclear Mn+ cation. The dehydrogenation reaction mechanistic investigations of cyclohexane catalyzed by MnNi+ and Mn+ have been carried out with density functional theory calculations. The activations of the first, third and fifth C–H bond of cyclohexane occur mainly because of the orbital interaction between the C–H σ bond of cyclic hydrocarbon and the empty d orbital of Mn. The smaller energy gaps of interacting orbitals result in stronger electron transfer between the related orbitals, which can elucidate MnNi+ cation is more reactive than Mn+. The coordination bonds between MnNi+ and cycloolefin in the second and third dehydrogenation processes of cyclohexane are another important factor for accelerating the dehydrogenation, which can stabilize the transition states for the activation of C–H bonds. The lower the transition state energy, the easier the C–H bond activation.

使用密度泛函理论(DFT)中的B3LYP方法对NiTi+催化环己烷的脱氢机理进行了系统的研究.得到了反应中所涉及到的优化几何构型和相关的几何参数,并绘制了相应的二重态和四重态势能面图.研究表明,NiTi+催化环己烷脱氢主要以同面脱氢为主,并且三次脱氢机理是相似的,主要产物是第一第二分子脱氢.

The mechanism of C-H bond activation of ethane was catalyzed by palladium halide cations (PdX+ (X = F, Cl, Br, H, and CH3)), which was investigated using density functional theory (DFT) at B3LYP level. The reaction mechanism was taken into account in triplet and singlet spin state potential energy surfaces. For PdF+, PdCl+, and PdBr+, the high spin states were the ground states, whereas the ground states were the low spin states in PdH+ and PdCH3+. The reaction of PdF+, PdCl+, and PdBr+ with ethane occurred via a typical "two-state reactivity" mechanism. In contrast, for PdH+ and PdCH3+, the overall reaction performed on the ground state PESs in a spin-conserving manner. The crossing points between two potential energy surfaces were observed and effectively decreased the activation barrier in PdX+/C2H6 (X = F, Cl, and Br). The minimum energy crossing points (MECP) were obtained used the algorithm in Harvey method. The natural valence electron configuration calculations were analyzed by natural bond orbital. The distribution and contribution of the front molecular orbital of the initial complexes could be further understand by the density of states. The feature of the bonding evolution in the main pathways was studied using topological analysis including localized orbital locator and atoms in molecules.

Quantum chemical calculations using density functional theory (DFT) at the B3LYP level have been performed to investigate the mechanism of dehydrogenation of cyclohexane catalyzed by NiTi+. A complete exploration of the quartet and doublet potential energy surfaces (PESs) was displayed. The result showed that the entire reaction proceeded in mixed PESs. In the dehydrogenation of cyclohexane catalyzed by NiTi+, there are two competing channels: CH bond activation and CC bond activation. Since higher energy was required to activate the CC bond, only exclusive CH bond activation was observed. To further explore the bonding patterns of NiTi+, natural bond orbital (NBO) analysis was performed. In addition, the density of states (DOS) analysis of the initial complexes was carried out. The result for NiTi+ activated cyclohexane was thoroughly compared with those for Ti2+ and Ni2+, meanwhile also against available data.

Heterometallic cations NiCu+ and CoNi+ can easily induce triple dehydrogenation of cyclohexane with high yield, and monometallic cations Ni+ and Co+ only give rise to double dehydrogenation with low yield. Reaction mechanisms of the six C-H bond activations for cyclohexane are systematically investigated by comparing the difference between bimetallic cations and monometallic ones. Fragment molecular orbital analysis clearly indicates that charge transfer (CT) occurs from the occupied interacting orbital of the metallic cation to the σ*-antibonding orbital of the first, third, and fifth activated C-H bonds in transition states. The synergistic effects of heteronuclear bimetallic cations result in the destabilization of the occupied interacting orbital in bimetallic cations, which raise the reactivity of bimetallic cations and enhance the CT between catalysts and substrates. Contrary to the absence of the third dehydrogenation product in the mononuclear metallic cation catalytic reaction, a significant amount of the third dehydrogenation product is observed in the presence of heteronuclear cations (NiCu+ and CoNi+). π back-bonding between Ni of heteronuclear metallic cations and the substrate cyclohexadiene plays an essential role in lowering the energies of transition states, which accelerate the third dehydrogenation. The reasons why heteronuclear bimetallic cations are more reactive than monometallic ones are discussed in detail.

本文合成了ZnPi-ZnPA(i=1～3)自组装卟啉,用核磁、质谱进行了相关的表征,并用密度泛函理论(DFT)从理论上研究了其在染料敏化太阳能电池中的光电行为.ZnPi-ZnPA(i=1～3)的最高占有分子轨道(HOMO)主要分布在冠卟啉,最低非占有分子轨道(LUMO)主要分布在锚定卟啉,这表明它们是良好的敏化剂.

In this paper, the mechanisms of H-2 evolution over the Mo-Edge of 2H-MoS2 with the unsaturated Mo (Mo-U) and S (S-U) were investigated by the density functional theory. The calculations indicated that Mo-U was a key active site for H-2 evolution. In the process of H-2 evolution, the S-U firstly absorbed H atom by the Volmer reaction, which caused the aggregation of electron on Mo-U, resulting in the barriers reduction of H transfer and H-2 evolution on Mo-U. The formation of molybdenum hydride was the rate-limiting step. Compared to Mo-edge in 2H-MoS2, the barrier of key step for H-2 evolution on Mo-edge with S-U and Mo-U decreased obviously. This implied that the removal fractional S from the Mo-edge of 2H-MoS2 could enhance its H-2 evolution activity and the electron trapping ability of active site for H-2 evolution by the Volmer-Heyrovsky reaction might affect its activity.

使用密度泛函理论(DFT)和B3LYP方法详细研究了Sc+催化环己烷同面及异面脱氢的反应机理.计算结果表明:Sc+与环己烷的反应在经过三次势能面的交叉后在低势能面上进行.且该势能面上每一个驻点的能量都低于反应物,该反应是一个无势垒的放热反应.三分子脱氢机理相似,整个脱氢反应释放出19 kcal/mol的能量.

The dehydrogenation reaction mechanism of cyclohexane catalyzed by dimer transition metal cluster V2+ has been investigated at the B3LYP/6-31G (d, p) level of density functional theory. Density of states (DOS) graph is used to understand more deeply the roles of the front molecular orbital of the initial complexes. After the first molecular dehydrogenation, the reaction mainly consists of two competition mechanisms. First, the C-H bonds of cyclohexane can be effectively activated by the V2+ cation, yielding the same-face dehydrogenation products. Second, the C-C bonds are activated, forming the different-face dehydrogenation products. Our calculations indicate that the reaction takes place more easily along the low-spin potential energy surface on the same-face and is a low-barrier or even barrier-free transformation. Carbon-carbon single bonds are nonpolar and generally far less reactive. A comparison of the reaction mechanism of V2+ and congener Ti2+ with cyclohexane has been presented. The bond dissociation energies (BDEs) of V2+ are greater than that of Ti2+, leading to difficulties in forming sandwich complexes in the different-face dehydrogenation of cyclohexane, and the same-face dehydrogenation is an important reaction channel.

以SD2染料分子在DSSC中的性能表现,为了拓宽SD2染料分子的光谱响应范围,降低最低空轨道与最高占用轨道之间的能级差值,现以SD2染料分子的电子给体和电子受体为基本框架,将其原来的吲哚单元和噻吩单元用一种共轭π桥(标记为A)和四种辅助电子受体(标记为1,2,3,4)替换.为了尽可能全面的表征新设计的16种染料分子在DSSC中的相关性能,前线分子轨道能级,紫外可见吸收光谱,自然键轨道分析,分子内电荷转移,电荷及空穴的重组能,短路电流密度和开路电压的相关参数通过量子化学的方法被一一计算出来.根据这些相关物理量的计算结果并结合这些染料分子在上述方面的表现,在这4个新设计的染料分子与二氧化钛结合,通过计算这4种配合物的几何构型,前线轨道分布,电子的垂直激发能,在三氯甲烷溶液中的紫外可见吸收光谱以及在激发过程中的轨道跃迁占比.

In light of the performance of the SD2 pigments in DSSC, in order to expand the absorption spectral scope, decrease the energy difference between the highest occupied and the lowest unoccupied molecular orbitals, with SD2 dye molecular electron donor and electron acceptor as the fundamental framework, the indole fragment and thiophene derivative in the prototype dye molecule were replaced by the two π-bridges (labeled PA, PB, respectively) and the four auxiliary electron acceptors (labeled A1, A2, A3, A4, respectively). For the sake of characterizing dye molecules as thoroughly as possible in DSSC, the frontier orbital energy levels, ultraviolet absorption spectra, natural bond orbital analysis, intramolecular charge transfer, charge and hole reorganization energies, parameters influencing the short-circuit current density and the open-circuit photovoltage for these eight individual dye molecules are carried out to try to fully characterize the properties of these dye molecules. According to these computational results of physical quantities and based on the performance of these dye molecules in the above aspects, in this paper, six free molecular models were picked out to combine with titanium dioxide cluster to calculate their geometrical structures, frontier orbital distributions, electron excitation energies, ultraviolet absorption spectra and the composition of the electronic transitions in chloroform solvent with polarizable continuum model. The results of these calculations show that the PA-A2 and PB-A4 dye molecule has better properties in electron transfer and spectral absorption range before and after the adsorption on the titanium dioxide.

Allyl alcohol could provide an interesting model for chemocontrol in transition metal-catalyzed insertion of carbenoid into O-H bond and olefin cyclopropanation. The chemoselectivity of PtCl2- and PtCl4-catalyzed (compared to Rh and Cu) reactions between methyl alpha-diazophenylacetate and unsaturated allyl alcohol has been carried out by DFT calculations. The potential energy profiles confirm that the intermediate free enol formed by intramolecular proton transfer is more favorable compared to the formation of the free ylide and cyclopropanation. The [1,3]-proton shift of the enol readily provides the final O-H insertion product, which has a barrier of 4.5 and 6.9 kcal/mol using metal-assisted two-allyl-alcohol clusters as a proton shuttle. Calculations provide a good explanation for the O-H insertion vs cyclopropanation of platinum, copper and rhodium catalysts have been used in these reactions. This study is expected to improve the understanding of platinum-catalyzed reactions for the C-X bond construction and provide guidance for the future design of new catalysts and new reactions.

This work investigated the adsorption of Eosin Y (EY) on the surface of Ru-4 and Pt-4 dusters and the UV-vis adsorption of EY by the DFT and TD-DFT method, respectively. The relationship of adsorption action, adsorption energy and hydrogen production efficiency in EY-sensitized system were studied as well. It is proved that the enhancement in the interaction energy of key group in sensitizer and co-catalyst was an efficient method to improve hydrogen evolution performance. The TD-DFT calculation showed that the photoelectrons of excited state EY mainly focused on the upper surface of C5O ring with the COO- side. In the EY-Ru-4 system, the maximum adsorption energy originated from the concurrent interaction of the COO- and C5O groups of EY with the Ru-4 cluster was -237.8 kJ/mol, while in the EY-Pt-4 system the maximum adsorption energy from the interaction between the C atom on C-6 ring of EY and the Pt-4 cluster was -230.5 kJ/mol. Compared with EY-Pt system, the dominating adsorption of EY on Ru was conducive to the quick transfer of photoelectron from EY to Ru. Therefore, the EY-Ru system exhibited higher hydrogen generation efficiency than the EY-Pt system.

The first thorough theoretical mechanism analysis of heteronuclear bimetallic cation NiAl+ with cyclohexane has been investigated on singlet and triplet potential energy surfaces (PESs) by using density functional theory. Our calculated results show that NiAl+ can assist in the decomposition of cyclohexane to form benzene through two types of reaction channel: C-H bond activation and H-2 formation; C-C bond activation and HD formation. The most important conclusion is that NiAl+ exhibits high efficiency and also high regioselectivity for C-H bond oxidation. However, the high zero-point vibrational energy (ZPVE) value for the cleavage of inert C-C bond is also the origin of its failure to form HD. In the process of the first C-H and C-C bond activations, crossing points (CPs) have been appeared between the two adiabatic surfaces, respectively. The minimum energy crossing points (MECPs) are gotten using the algorithmin Harvey method. Density of states (DOS) is used to obtain a deeper understanding for the roles of the front molecular orbital of the initial complexes. The bonding properties of the special intermediates involved in the process of C-C bond activations are discussed by the IR spectrum methods. (C) 2018 Elsevier B.V. All rights reserved.

Three organic electron donors (T1, T2 and T3) were creatively synthesized by researchers, based on their extraordinary characteristics under the experimental conditions. The three original donors were selected and designed to substitute the primary donors of two dye molecules of different types LJ1 (D–π–A) and WS4 (D–A–π–A). In the subsequent theoretical investigations, density functional theory (DFT) and time-dependent DFT (TD-DFT) were employed to explore and simulate the fundamental parameters for these six potential sensitizers in dye-sensitized solar cells (DSSCs). For the essential parameters in evaluating the energy conversion process, such as oscillator strength (f) and light harvesting efficiency (LHE), the driving force of electron injection (ΔGinject) vertical dipole moments (μnormal) and driving force of regeneration (ΔGregen) were simulated. In addition, energy levels and the orbital compositions, absorption spectra, natural bond orbital (NBO) analysis from S0 to S1, distance between hole and electron centroid (DCT), average hole-electron distance (Δr) upon photoexcitation, overlap distance of hole and electron (S), transferred charge (ΔQ) for intramolecular charge transfer (ICT) processing, excited lifetime and electron injection lifetime of the six chromophores were systematically computed. Because of the different configurations formed in the donor motif, the correlative properties of the six newly designed sensitizers compared with prototype sensitizers of LJ1 and WS4 were altered and promoted significantly.

染料敏化太阳能电池能够充分利用太阳能使非金属有机染料得到很好的发展.量子化学是敏化剂设计策略的有效手段.本文采用量子化学方法探究了具有D-π-A构型的敏化剂分子的刚性π桥结构的性质,通过对一系列影响电池性能的关键因素进行理论表征,揭示了敏化剂分子结构与电池效率之间的关系,并且筛选出具有发展潜力的染料分子.

采用密度泛函理论(DFT)下的B3LYP方法计算研究了Cr2+活化环己烷的同面脱氢反应机理.计算结果表明,Cr2+催化环己烷同面脱氢首先活化环己烷的C—H键,进而发生氢原子的转移和氢分子消除.Cr2+与环己烷的脱氢反应是在低自旋态势能面上进行的一个无势垒的放热反应,三分子脱氢反应机理相似,整个脱氢反应放热74.67kcal·mo1-1.

In this paper, the reaction mechanism for N2O with CO on the surface of Ni-5 cluster was investigated by the B3LYP method of density functional theory (DFT). Ni atom of various species was calculated using B3LYP/LANL2DZ basis set, and C, N, O atoms at B3LYP/6-31G* level. In the temperature range of 100-1000K, the statistical thermodynamics and Eyring transition state theory with Winger correction were used to study the kinetic characters of reaction. The calculation results indicated that the reaction of N2O with CO on Ni-5 cluster had two major reacting processes: (1) O atom first dissociated from N2O on Ni-5 cluster, and then reacted with CO on Ni-5 and (2) on the surface of Ni-5 catalyst, 0 atom of N2O direct interacted with C atom of CO, resulting into the dissociation of N2O and the form of CO2. The direct O extractinn channel was the main channel due to its low potential energy and high rate constant. (C) 2017 Elsevier B.V. All rights reserved.

In this paper, the mechanisms of H2 evolution on Pt6, Pt5Sn5, and Pt3Sn6 clusters were respectively investigated by the B3LYP method of density functional theory (DFT). The B3LYP functional with non-local dispersion corrections (B3LYP-D3) method were performed to investigate the adsorption of H and H+ on clusters. The calculation results indicated that the adsorption energy of H on Pt reduced due to the interaction of Sn and Pt, which promoted H desorption from Pt to form H2. Meanwhile, Sn atom of Pt5Sn5 and Pt3Sn6 clusters had strong interaction with H+ due to the existence of Pt, which was benefit for the reduction of H+ on Sn atom. As a consequence, Pt5Sn5 and Pt3Sn6 showed lower potential barrier and higher activities than Pt for H2 evolution. The potential barriers of H2 formation over Pt3Sn6 clusters was only 11.1% of that over Pt cluster.