金属原子（离子）-苯配合物的电子转移反应

用密度泛函理论（ＤＦＴ／ＢＬＹＰ）在６－３１Ｇ基组水平上研究了金属原子－苯与离子－苯配合物的气相电子转移过程,得到了Ｍ（Ｌｉ,Ｎａ,Ｍｇ）－Ｃ６Ｈ６和Ｍ＾＋－Ｃ６Ｈ６络合物以及它们之间电子转移过程的先驱络合物的最优几何构型和电子结构。同时,利用线性坐标确定了过滤态的结构,结果表明：ＤＦＴ方法计算得到的单体,即原子（离子）－苯的构型,同ＭＰ２结果较为一致。先驱络合物具有Ｃ６ν对称性,给体与受体间距离     

Inner Sphere Reorganization Energy for the Electron Transfer Reactions between M-C_6H_6 and M~ -C_6H_6 Complexes in Gaseous phase: An ab initio Computation

IntroductionTheelectrontransfer(ET)reactionisanfundamentalchemicalprocessandhasbecomethefocusoftheoreticalandexperimentalstudies1-3.AsuitableapproachtowardunderstandingtheETreactivitypatternsistoseparatethevariouscontributionsintoexponentialandpre-exponentialfactors.Theexponentialparts,i.e.,theFrank-Condonfactor,isacompositeofthestructuralreorganizationofthereactingsystemimmediate1yaftertheelectrontransfered.Basedonthecharacteristicsofthereactingsystem'sstructure,thereorganizationenergy(RE…     

Ab initio calculation for inner reorganization energy of gas-phase electron transfer in organic molecule–ion systems

A series of electron transfer (ET) reactions between some organic molecules have been investigated through ab initio calculations. Biphenyl (Bp) and 9,9^′-dimethylfluorene anion radicals are chosen as the donor, whereas several organic molecules with different redox abilities are chosen as the acceptor. The inner reorganization energy and the endothermicity of the ET reactions in those molecule–ion systems have been estimated through the HFSCF and complete active space multiconfiguration SCF calculations. Double-well potentials for the gas-phase ET reactions have been constructed using the linear reaction coordinate, and the results show that the quinone-containing ET reactions are in Marcus' inverted region. It has been found that the inner reorganization energies are different for various donor-acceptor couples, unlike the experimentally fitted ones. The contribution from the inter-ring torsional motion in Bp to the inner reorganization energy has been evaluated from the energy difference of the biphenyl-acceptor and the dimethylfluorine-acceptor systems. Comparisons with the experimentally observed results have been made.     

The Inner-sphere Reorganization Energy of M-H/M~ -H System in Gaseous Phase

IntroductionTheETreactionisanimportantfundamentalchemicalprocessandhasbecomethefocusoftheoreticalandexperimentalstudies'-3.AsanimportantparametertocharacterizethekineticsoftheETprocess,RErepresentstheenergychangeassociatedwiththestructuralchangeofthereactantsandtheirimmediateenvironments.Forthereactingsystemingaseousphase,theouter-sphereREisvirtuallyzeroindicatingweakinteractionbetweenthereactantandthesurroundingmedium,sotheinfluenceofinnerspherestructuralreorganizationpredondnatesthewhole…     

Ab initio quantum mechanical/molecular mechanical simulation of electron transfer process: fractional electron approach

Electron transfer (ET) reactions are one of the most important processes in chemistry and biology. Because of the quantum nature of the processes and the complicated roles of the solvent, theoretical study of ET processes is challenging. To simulate ET processes at the electronic level, we have developed an efficient density functional theory (DFT) quantum mechanical (QM)/molecular mechanical (MM) approach that uses the fractional number of electrons as the order parameter to calculate the redox free energy of ET reactions in solution. We applied this method to study the ET reactions of the aqueous metal complexes Fe(H(2)O)(6)(2+/3+) and Ru(H(2)O)(6)(2+/3+). The calculated oxidation potentials, 5.82 eV for Fe(II/III) and 5.14 eV for Ru(II/III), agree well with the experimental data, 5.50 and 4.96 eV, for iron and ruthenium, respectively. Furthermore, we have constructed the diabatic free energy surfaces from histogram analysis based on the molecular dynamics trajectories. The resulting reorganization energy and the diabatic activation energy also show good agreement with experimental data. Our calculations show that using the fractional number of electrons (FNE) as the order parameter in the thermodynamic integration process leads to efficient sampling and validate the ab initio QM/MM approach in the calculation of redox free energies.     

Theoretical Study of the Inner/sphere Reorganization Energy and Activation Energy of Self/exchange Electron Transfer Reaction for M(H2O)26+/3+ (M=V, Cr, Mn, Fe and Co) Systems

通过建立电子转移过程的活化模型和重组模型, 提出了用量子化学从头算方法研究电子转移过程内层重组能和活化能的新方法. 在UMP26/311G水平上获得了5对过渡金属水合离子体系M(H     

Mono- and dinuclear ruthenium complexes of bridging ligands incorporating two di-2-pyridylamine motifs: Synthesis, spectroscopy and electrochemistry

Mono- and dinuclear ruthenium(II) complexes of six bridging ligands that contain a central arene (phenyl, naphthalenyl or biphenyl) core to which are attached two di-2-pyridylamine groups have been prepared. These complexes possess six-membered chelate rings. Full assignments of their ¹H NMR spectra are described which provides insight into the comformations of the ligands in these complexes. The extent of metal–metal communication in the dinuclear complexes was probed by electrochemical measurements and related to metal–metal distances.     

Ab initio study of long-range electron transfer between biphenyl anion radical and naphthalene

After the separation of the donor, the acceptor, and the σ-type bridge from the π-σ-π system, the geometries of biphenyl, biphenyl anion radical, naphthalene, and naphthalene anion radical are optimized, and then the reorganization energy for the intermolecular electron transfer (ET) at the levels of HF/4-31G and HF/DZP is calculated. The ET matrix elements of the self-exchange reactions of theπ-σ-π systems have been calculated by means of both the direct calculation based on the variational principle, and the transition energy between the molecular orbitals at the linear coordinateR = 0.5. For the cross reactions, the ET matrix element and the geometry of the transition state are determined by searching the minimum energy splitting Δ_min along the reaction coordinate. In the evaluation of the solvent reorganization energy of the ET in solution, the Marcus’ two- sphere model has been invoked. A few of ET rate constants for the intramolecular ET reactions for the π-σ-π systems, which contain the biphenylyl as the donor and both biphenylyl and naphthyl as the acceptor, have been obtained. Project supported by the National Natural Science Foundation of China (Grant Nos. 29706104 and 29573112), the State Key Laboratory of Theoretical and Computational Chemistry of Jilin University.     

生物体系中电子转移机理的理论研究Ⅰ: 一种计算电子转移 的方法及在螺环化 合物中的应用

应用"相应轨道变换"和"广义"密度矩阵的方法,向MOPAC程序包中加入了新的功能,使其能处理电子转移反应中的部分参数。然后用此程序包中AM1方法对具有螺环结构的分子进行处理,计算了化合物在不同外加电场强度下的势能面、反应热ΔE,重组能λ及电子转移矩阵元V~A~B,结果表明,λ,V~A~B受外加电场的影响较小,而ΔE则与之成正比。对标题化合物1的计算结果也同abinitio法的结果进行了比较,发现其变化趋势完全一致,这说明本方法在计算电子转移方面是可靠的。与abinitio方法相比,本程序不仅适用于计算较大体系(如生物大分子),而且还具有速度快,耗时少的优点。     

The evaluation of bond dissociation energies for simple sulphur containing molecules using ab initio and density functional methods

The S–H and C–S bond dissociation energies for simple alkylthiols and dialkylsulphides, along with the S–S bond dissociation energy for dimethyl disulphide, compounds which have been used in the metal–organic chemical vapour deposition (MOCVD) growth of wide band gap II–VI (12–16) Zn- and Cd-based compound semiconductors, have been computed using the ab initio (ROHF and MP2) and density functional theory (DFT) methods (BHandH, BHandHLYP, B3LYP, B3P86, B3PW91, BLYP and BP86) with the 6-311+G(2d,p) basis set along with high accuracy complete basis set, CBS-4 and CBS-Q energy computations. The computed energies are compared with experimental results and the suitability of the DFT methods, for the computational study of these systems, is discussed.     

Inner‐sphere reorganization for redox pairs M(NH3)62+/3+ (M=Mn,Fe, and Co): Models and calculations

The inner‐shell reorganization and activation models of the electron‐transfer reactions of transition‐metal hexammine complexes are presented. The inner‐shell reorganization and activation energies of several hexammine redox pairs M(NH₃)₆^2+/3+ (M=Mn, Fe, and Co) in self‐exchange reactions are studied by different formalisms. The extent of the anharmonicities in the vibration between the metal–ion and the ligands in the reorganization process of these complexes is determined. The inner‐shell barriers of these redox pairs are dependent on reorganization model used. The contribution of the individual reactants to the inner‐shell barrier is sensitive to the model used. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001     

Internal reorganization energy in return electron transfer within geminate radical ion pairs

The internal reorganization energies λ_v for return electron transfer (ET) reactions within geminate radical ion pairs were studied using the extended Nelsen method. In the ET systems studied, the common acceptor was 9,10-dicyanoanthracene (DCA). The donors were methyl-substituted compounds of benzene, biphenyl, naphthalene and phenanthrene. The calculated results indicated that the λ_v values were associated mainly with the carbon atoms of the aromatic rings and the atoms linked directly to the aromatic rings. Systems with similar substituted conditions are expected to have similar internal reorganization energies. For systems in which the two aromatic rings of the donor can rotate relative to each other, the calculated λ_v values include a contribution from the change in torsional angle in the ET process. Compared with the system in which the donor is a fluorene molecule, the contributions of the torsional angles (low-frequency vibration) to λ_v were estimated.     

肽链体系中的长程电子转移: 多肽构象和旁链间距对电子转移矩阵元的影响

用AM1半经验方法,优化了吲哚和苯酚中性分子、正离子自由基和负离子自由基的几何构型。用线性反应坐标近似和溶剂效庆的类导体屏蔽模型（COSMO）构造吲哚正离子和苯酚中性分子间电子转移的双势阱,用以估算多肽链中色氨酸和酪氨酸之间的电子转移的反应热和内重组能。优化TrpH-(Pro)n-TyrOH(n=0-3)多肽模型分子的结构和构象,用能级分裂因子的极小值方法计算了这些多肽体系的电子转移矩阵元。     

Theoretical insights and design of Ru(II)-based complexes with DNA-photocleavage properties

A theoretical research on the properties of Ru(II)-based complexes 1–5 with polypyridyl ligands damaging DNA with the help of light has been carried out. Firstly, the redox potential, electrons-transfer (ET) activation energy, and intra-molecular reorganization energy were computed using DFT (density functional theory), and the results can be used to explain the DNA-photocleavage efficiencies of complexes. Secondly, the effect of ligands on the reduction potentials of complexes in the excited state was elucidated, and the reason of complexes cleaving DNA by the oxidation-reduction reaction and the produced singlet oxygen was explained. Finally, the frontier orbitals of complexes were computed, which was used to qualitatively explain the reason of complexes with high reduction potentials in the excited state.     

Determination of protonation- and metal complex stability constants for a chelating monomer and its immobilized in polymer resin

An improved method is described for the calculation of complex stability constants for metal–ligand complexes considering ligands immobilized in resin phase. The applicability of it has been proved for N′-benzylethylene diamine N,N,N′-triacetic acid monomer (BEDTA) and for the ion exchange resin developed in the authors laboratory immobilizing this with styrene divinyl benzene. Calcium and magnesium metal ion complexes were investigated. Electrochemical and flame photometric measurements were used to collect equilibrium concentration data. The procedure worked out included the measurement of the quantity of resin bound water. Using these and the other experimentally gathered values and the improved way of calculation metal ligand complex stability constants were determined in aqueous media. Ion exchange chromatographic separation of calcium and magnesium ions was performed with a resin containing column for separation and optimized eluent.     

Spin-inversion mechanisms in the reactions of transition metal cations (Sc+, Ti+, V+, Cr+, Mn+, Fe+, Co+, Ni+, and Cu+) with OCS in the gas phase: A perspective from automated reaction path search calculations

The mechanisms including spin-inversion have been systematically studied for the M⁺ + OCS → MS⁺ + CO/MO⁺ + CS (M denotes a transition metal from Sc to Cu) ion-molecule reactions using the automated reaction path search method. We used the lowest mixed-spin potential energy surface obtained from the diagonalization of the spin-coupled Hamiltonian matrix, whose diagonal elements are taken to be the lowest two spin states. This scheme can effectively locate approximate minimum energy crossing points between the two potential energy surfaces with different spin multiplicities. The spin-orbit couplings at spin-inversion points have been calculated to understand the efficiencies of nonadiabatic transitions. The obtained reaction pathways and the calculated spin-orbit couplings are employed to interpret previous experimental studies.     

Electron Transfer Reaction between M-C_6H_6 and M~ -C_6H_6 Complexes in the Gas Phase: Density Functional Theory Study

Significant progress has been made in understanding the nature of the transition state andthe paths for electron transfer, especially the influences of environmental factors and themolecular properties on the electron transfer rate. These classical and semi-classical, aswell as quantum-mechanical theory, have been very successful in rationalizing severalstructure-reactivity relationships and in predicting novel features of reactivity. Thesemodels established some links between the electron tra…     

Quantum versus classical electron transfer energy as reaction coordinate for the aqueous Ru2+/Ru3+ redox reaction

Applying density functional theory (DFT)-based molecular dynamics simulation methods we investigate the effect of explicit treatment of electronic structure on the solvation free energy of aqueous Ru²⁺ and Ru³⁺.Our approach is based on the Marcus theory of redox half reactions, focussing on the vertical energy gap for reduction or oxidation of a single aqua ion. We compare the fluctuations of the quantum and classical energy gap along the same equilibrium ab initio molecular dynamics trajectory for each oxidation state. The classical gap is evaluated using a standard point charge model for the charge distribution of the solvent molecules (water). The quantum gap is computed from the full DFT electronic ground state energies of reduced and oxidized species, thereby accounting for the delocalization of the electron in the donor orbital and reorganization of the electron cloud after electron transfer (ET). The fluctuations of the quantum ET energy are well approximated by gaussian statistics giving rise to parabolic free energy profiles. The curvature is found to be independent of the oxidation state in agreement with the linear response assumption underlying Marcus theory. By contrast, the diabatic free energy curves evaluated using the classical gap as order parameter, while also quadratic, are asymmetric reflecting the difference in oxidation state. The response of these two order parameters is further analysed by a comparison of the spectral density of the fluctuations and the corresponding reorganization free energies.     

Distance dependence analysis of the electron transfer reactivity for the metastable FeOH2/FeOH2 system: an ab initio investigation

A novel theoretical scheme and ab initio application in discussing the electron transfer (ET) reactivity are presented in this paper, and are also calibrated in terms of the mono-hydrated iron ion system, Fe²⁺–OH₂/Fe³⁺–OH₂. The detailed geometry optimizations have been made at UMP2(full)/6-311+G^* level, and the activation geometrical configuration and the energy have been obtained at this level of theory using the activation model and the ab initio potential energy surface fitted from MP2(full)/6-311+G^* single point energies. The corresponding energy quantities (such as the activation energy, and dissociation energy) have also been obtained at different levels of theory (HF, MP2, MP3, MP4, QCISD and PUHF, PMP2 and PMP3 with the spin-projection) and a same basis set (6-311+G^*). The electron correlation calculations include the all electron correlation and the valence electron correlation. The electronic transmission coefficient is calculated using the ab initio potential energy surface slopes and the coupling matrix element determined from the two-state model and the Slater-type d-electron wave functions. The pair distribution function is calculated using two different schemes. Taking the pair distribution function and the local ET rate into account, a statistically averaged overall observed ET rate scheme and a spherically averaged local ET rate scheme are proposed. The relevant kinetic parameters are obtained in terms of these new schemes at different ab initio calculational levels. The contact distance dependence of these parameters and the applicability of the presented models and ab initio calculational method are also discussed.     

To be or not to be NO in coordination chemistry? A mechanistic approach

In this review, the reactions of nitric oxide with selected metal complexes of biological and environmental importance are reviewed. Fundamental chemical kinetics and mechanisms that lead to the formation and decay of nitrosyl complexes are illustrated and discussed on the basis of work on Fe(II) chelate complexes and selected biomolecules such as metmyoglobin and cobalamin. In the context of common interference of higher nitrogen oxides in the studies on the interactions of nitric oxide with metal centres, the reactions of NO₂⁻/HONO (in aqueous media) and NO₂/N₂O₃ (in aprotic media) with metal complexes are described on the basis of selected examples. Throughout the review the focus is on the mechanistic details of the binding of NO to and the release of NO from metal complexes, and the nature of the stable metal–NO complexes produced in solution.