CH···π interactions do not contribute to hydrogen transfer catalysis by glycerol dehydratase

The role of the nonbonded CH···π interaction in the hydrogen abstraction from glycerol by the coenzyme B(12)-independent glycerol dehydratase (GDH) was examined using the QM/MM (ONIOM), MP2, and CCSD(T) methods. The studied CH···π interaction included the hydrogen atom of the -C(2)H(OH)- group of the glycerol substrate and the tyrosine-339 residue of the dehydratase. A contribution of this interaction to the stabilization of the transition state for the transfer of a hydrogen atom from the adjacent terminal C(1)H(2)(OH) group to cysteine 433 was determined by ab initio HF, MP2, and CCSD(T) calculations with the aug-cc-pvDZ basis set for the corresponding methane/benzene, methanol/phenol, and glycerol radical/phenol subsystems. The calculated CH···π distance, defined as the distance between the H atom and the center of the phenol ring, shortened from 2.62 to 2.52 ? upon going from the ground- to the transition-state of the GDH-catalyzed reaction. However, this shortening was not accompanied by the expected lowering of the CH···π interaction free energy. Instead, this interaction remained weak (about -1 kcal/mol) along the entire reaction coordinate. Additionally, the mutual orientation of the CH group and the phenol ring did not change significantly during the reaction. These results suggest that the phenol group of the tyrosine-339 does not contribute to lowering the activation barrier in the enzyme, but do not exclude the possibility that tyrosine 339 facilitates proper orientation of glycerol for the electrostatic catalysis, or inhibits side-reactions of the reactive glycerol radical intermediate.     

·OH自由基与CH3CN反应机理及动力学

在CBS-QB3水平上研究了CH3CN 和·OH反应的势能面, 其中包括两个中间体和9个反应过渡态. 分别给出了各主要物质的稳定构型、相对能量及各反应路径的能垒. 根据计算的CBS-QB3势能面, 探讨了CH3CN+·OH反应机理. 计算结果表明, 生成产物P1(·CH2CN+H2O)的反应路径在整个反应体系中占主要地位. 运用过渡态理论对产物通道P1(·CH2CN+H2O)的速率常数k1(cm3·molecule-1·s-1)进行了计算. 预测了k1(cm3·molecule-1·s-1)在250-3000 K温度范围内的速率常数表达式为k1(250-3000 K)=2.06×10^-20T^3.045exp(-780.00/T). 通过与已有的实验值进行对比得出, 在实验所测定的250-320 K 范围内, 计算得到的k1的数值与已有的实验值比较吻合. 由初始反应物生成产物P1 (·CH2CN+H2O)只需要克服一个14.2 kJ·mol-1的能垒. 而产物·CH2CN+H2O生成后要重新回到初始反应物CH3CN+·OH, 则需要克服一个高达111.2 kJ·mol-1的能垒,这就表明一旦产物P1生成后就很难再回到初始反应物.     

Hydrothermal Synthesis,Crystal Structure and Thermal Stability Properties of the Complex [Cd2(phen)2(C14HuO3)4(CH3CH2OH)]·(CH3OH)·(H2O)

T A dinuclear cadmium complex[Cd2(phen)2(C14H11O3)4(CH3CH2OH)]·(CH3OH)·(H2O)has been synthesized with benzilic acid and 1,10-phenanthroline by hydrothermal method.The crystal structure was determined bv X-ray diffraction with crystal parameters as follows:triclinic system with space group P-1,α=1.21298(10),b=1.32586(1 1),c=2.4815(2)nm,α=76.2630(10),β=81.4500(10),γ=69.1700(10)°V=3.6143(5)nm3,Dc=1.438g/cm3,Z=1,F(000)=1600,the final GOOF=0.937,R=0.0521 and wR=0.1328.In the title complex,the dinuclear structure is defined by carboxyl oxygen atoms adopting a monodentate bridged coordination mode.The coordination environment of Cd(Ⅱ)ion is CdO4N2,giving a distorted octahedral coordination geometry.TG analysis shows that the title complex is stable under 140℃.     

Ab initio reaction kinetics of hydrogen abstraction from methyl formate by hydrogen, methyl, oxygen, hydroxyl, and hydroperoxy radicals

Combustion of renewable biofuels, including energy-dense biodiesel, is expected to contribute significantly toward meeting future energy demands in the transportation sector. Elucidating detailed reaction mechanisms will be crucial to understanding biodiesel combustion, and hydrogen abstraction reactions are expected to dominate biodiesel combustion during ignition. In this work, we investigate hydrogen abstraction by the radicals H·, CH(3)·, O·, HO(2)·, and OH· from methyl formate, the simplest surrogate for complex biodiesels. We evaluate the H abstraction barrier heights and reaction enthalpies, using multireference correlated wave function methods including size-extensivity corrections and extrapolation to the complete basis set limit. The barrier heights predicted for abstraction by H·, CH(3)·, and O· are in excellent agreement with derived experimental values, with errors ≤1 kcal/mol. We also predict the reaction energetics for forming reactant complexes, transition states, and product complexes for reactions involving HO(2)· and OH·. High-pressure-limit rate constants are computed using transition state theory within the separable-hindered-rotor approximation for torsions and the harmonic oscillator approximation for other vibrational modes. The predicted rate constants differ significantly from those appearing in the latest combustion kinetics models of these reactions.     

Methane activation by titanium monoxide molecules: a matrix isolation infrared spectroscopic and theoretical study

Reactions of titanium monoxides with methane have been investigated using matrix isolation infrared spectroscopy and theoretical calculations. Titanium derivatives of several simple oxyhydrocarbons have been prepared and identified. The titanium monoxide molecules prepared by laser evaporation of bulk TiO2 target reacted with methane to form the TiO(CH4) complex in solid argon, which was predicted to have C3v symmetry with the oxygen atom coordinated to one hydrogen atom of the methane molecule. The complex rearranged to the CH3Ti(O)H titano-acetaldehyde molecule upon visible (lambda > 500 nm) irradiation. The titano-acetaldehyde molecule sustained further photochemical rearrangement to the CH2Ti(H)OH titano-vinyl alcohol molecule, which was characterized to be a simple carbene complex involving agostic bonding. The CH2Ti(H)OH molecule reacted with a second methane to form the (CH3)2Ti(H)OH titano-isopropyl alcohol molecule spontaneously on annealing. The (CH3)2Ti(H)OH molecule also can be produced via UV photon-induced rearrangement of the CH3Ti(O)H(CH4) complex.     

Synthesis and Crystal Structure of a Novel Tetranuclear Manganese(II) Complex with a Tripodal Peptide Ligand

1 INTRODUCTION Amides play an important role in the evolution ofnature. The amidate participates in the coordinationof iron with the ligands containing biomolecules, suchas antitumor drug bleomycin[1] and nitrile hydra-tase[2]. Bleomycin is a clinically useful antitumoragent which catalyzes the cleavage of oxidative DNAand oxidizes a number of organic substrates with di-oxygen or H2O2 . This has raised more interest in [3]the coordination of amide complexes[4, . …     

Cu_2O(111)催化水煤气变换反应机理的理论研究

采用密度泛函理论结合周期平板模型方法系统地研究了水煤气变换反应在Cu_2O(111)表面上的反应机理,包括氧化还原机理、羧基机理和甲酸根机理.结果表明,在Cu_2O(111)表面,羧基机理和甲酸根机理均可行,且甲酸根机理更为有利,其最佳反应途径为H_2O~*→H~*+OH~*;CO(g)+H~*+OH~*→trans-HCOOH~*(1)→cis-HCOOH~*→CO_2~*+H_2(g).其中trans-HCOOH~*(1)→cis-HCOOH~*为其决速步,该基元反应的能垒仅为59 kJ·mol~(-1).羧基机理的最优反应路径同样是以H_2O的解离反应开始,随后CO(g)+OH~*→cis-COOH~*→trans-COOH~*→CO_2(g)+H~*,最后产生的两个吸附的H原子先迁移再结合生成H_2,整个反应的控速步骤为H原子的迁移,迁移能垒为96 kJ·mol~(-1).氧化还原机理则由于OH解离需要越过一个很高的能垒(254 vs.187 kJ·mol~(-1))而不可行.     

Cu(111)面上糠醇加氢生成2-甲基呋喃的反应机理

采用广义梯度近似的密度泛函理论并结合平板模型的方法,详细研究了糠醇在Cu(111)面上反应生成2-甲基呋喃的反应历程,优化了糠醇在Cu(111)面的吸附模型,并采用完全线性同步和二次同步变换的方法,对三种可能的反应机理中的各反应步骤进行了过渡态搜索.结果表明,糠醇主要通过支链上OH与Cu(111)面相互作用,易形成ψCH2和ψCH2O中间体(ψ代表呋喃环).糠醇进一步加氢机理很可能为:引入的氢物种明显降低了糠醇分解形成的中间体ψCH2的活化能,并促进了它的形成;中间体ψCH2更易从糠醇中获得H而生成2-甲基呋喃.该过程的控速步骤为ψCH2O*→ψCHO*+H*,活化能为199.0kJ/mol,总反应是2ψCH2OH=ψCH3+ψCHO+H2O.     

Reactions of the ionized enol tautomer of acetanilide: elimination of HNCO via a novel rearrangement

The reactions of ionised acetanilide, C(6)H(5)NH(=O)CH(3)(.+), and its enol, C(6)H(5)NH(OH)=CH(2)(.+), have been studied by a combination of tandem mass spectrometric and computational methods. These two isomeric radical cations have distinct chemistries at low internal energies. The keto tautomer eliminates exclusively CH(2)=C=O to give ionised aniline. In contrast, the enol tautomer loses H-N=C=O, via an unusual skeletal rearrangement, to form predominantly ionised methylene cyclohexadiene. Hydrogen atom loss also occurs from the enol tautomer, with the formation of protonated oxindole. The mechanisms for H-N=C=O and hydrogen atom loss both involve cyclisation; the former proceeds via a spiro transition state formed by attachment of the methylene group to the ipso position, whereas the latter entails the formation of a five-membered ring by attachment to the ortho position. The behaviour of labelled analogues reveals that these two processes have different site selectivities. Hydrogen atom loss involves a reverse critical energy and is subject to an isotope effect. Surprisingly, attempts to promote the enolisation of ionised acetanilide by proton-transport catalysis were unsuccessful. In a reversal of the usual situation for ionised carbonyl compounds, ionised acetanilide is actually more stable than its enol tautomer. The enol tautomer was resistant to proton-transport catalysed ketonisation to ionised acetanilide, possibly because the favoured geometry of the encounter complex with the base molecule is inappropriate for facilitating tautomerisation.     

The behavior of oxygen as a collision-induced dissociation target gas

The unusual and unique ability of O2 as target gas in kV collision-induced dissociations, to enhance a specific fragmentation of a mass selected ion, has been examined in detail. The affected dissociations studied were the loss of CH3* from CH3CH+X (X = OH, CH3, NH2, SH); CH3* and C1* loss from CH3C+(C1)CH3; C2H5* loss from CH3CH2CH+X (X = OH and NH2); H* loss from +CH2OH and +CH2NH2; O loss from 1,2-, 1,3-, and 1,4-C6H4(NO2)2+*; CH3NO+*; C6HsNO2+*; C5H5NO+* (pyridine N-oxide); 3- and 4-CH3C5H4NO+*. A general explanation of the phenomena, which was semiquantitatively tested in the present work, can be summarized as follows: the ion - O2 encounter excites the target molecules to their 3sigma(g)- state which resonantly return this energy to electronic state(s) in the ion. The excited ion now contains a sharp excess of a narrow range of internal energies, thus significantly and only enhancing fragmentations whose activation energies lie within this small energy manifold.     

Selective surface decoration of corannulene

The reaction of corannulene (C(20)H(10)) with 1,2-C(2)H(4)Hal(2) (Hal = Cl or Br) in the presence of AlCl(3) affords stable nonplanar carbocations C(20)H(10)CH(2)CH(2)Hal(+) (Hal = Cl (1) and Br (2)) with an -CH(2)CH(2)Hal moiety attached to the interior carbon atom of the bowl. In the analogous reaction with 1-bromo-2-chloroethane, the selective (up to 98%) abstraction of chloride is observed with the formation of cation 2. The molecular structures of bowl-shaped carbocations 1 and 2 crystallized as salts with AlCl(4)(-) counterions are revealed by single-crystal X-ray diffraction. The reaction of 2 with methanol or ethanol provides further decoration of the nonplanar polyarene upon the nucleophilic addition of alkoxy groups to the exterior carbon atom of the corannulene moiety. The (1)H NMR investigation of the corresponding products, C(20)H(10)(CH(2)CH(2)Br)(OCH(2)R) (R = H (3) and CH(3) (4)), shows the formation of intramolecular H···O and H···Br hydrogen bonds.     

A crossed molecular beam study of the O(1D) + C(3)H(8) reaction: multiple reaction pathways.

The O((1)D) + C(3)H(8) reaction has been reinvestigated using the universal crossed molecular beam method. Three reaction channels, CH(3) + C(2)H(4)OH, C(2)H(5) + CH(2)OH, and OH + C(3)H(7), have been observed. All three channels are significant in the title reaction with the C(2)H(5) formation process to be the most important, while the CH(3) formation and the OH formation channels are about equal. Product kinetic energy distributions and angular distributions have been determined for the three reaction channels observed. The oxygen-containing radicals in the CH(3) and C(2)H(5) formation pathways show forward-backward symmetric angular distribution relative to the O atom beam, while the OH product shows a clearly forward angular distribution. These results indicate that the OH formation channel seems to exhibit different dynamics from the CH(3) and C(2)H(5) channels.     

An abiotic analogue of the diiron(IV)oxo "diamond core" of soluble methane monooxygenase generated by direct activation of O2 in aqueous Fe(II)/EDTA solutions: thermodynamics and electronic structure

We study the generation of a dinuclear Fe(IV)oxo species, [EDTAH·FeO·OFe·EDTAH](2-), in aqueous solution at room temperature using Density Functional Theory (DFT) and Ab Initio Molecular Dynamics (AIMD). This species has been postulated as an intermediate in the multi-step mechanism of autoxidation of Fe(II) to Fe(III) in the presence of atmospheric O(2) and EDTA ligand in water. We examine the formation of [EDTAH·FeO·OFe·EDTAH](2-) by direct cleavage of O(2), and the effects of solvation on the spin state and O-O cleavage barrier. We also study the reactivity of the resulting dinuclear Fe(IV)oxo system in CH(4) hydroxylation, and its tendency to decompose to mononuclear Fe(IV)oxo species. The presence of the solvent is shown to play a crucial role, determining important changes in all these processes compared to the gas phase. We show that, in water solution, [EDTAH·FeO·OFe·EDTAH](2-) (as well as its precursor [EDTAH·Fe·O(2)·Fe·EDTAH](2-)) exists as stable species in a S = 4 ground spin state when hydrogen-bonded to a single water molecule. Its structure comprises two facing Fe(IV)oxo groups, in an arrangement similar to the one evinced for the active centre of intermediate Q of soluble Methane Monooxygenase (sMMO). The inclusion of the water molecule in the complex decreases the overall symmetry of the system, and brings about important changes in the energy and spatial distribution of orbitals of the Fe(IV)oxo groups relative to the gas phase. In particular, the virtual 3σ* orbital of one of the Fe(IV)oxo groups experiences much reduced repulsive orbital interactions from ligand orbitals, and its consequent stabilisation dramatically enhances the electrophilic character of the complex, compared to the symmetrical non-hydrated species, and its ability to act as an acceptor of a H atom from the CH(4) substrate. The computed free energy barrier for H abstraction is 28.2 kJ mol(-1) (at the BLYP level of DFT), considerably below the gas phase value for monomeric [FeO·EDTAH](-), and much below the solution value for the prototype hydrated ferryl ion [FeO(H(2)O)(5)](2+).     

Intriguing roles of reactive intermediates in dissociation chemistry of N-phenylcinnamides

In mass spectrometry of protonated N-phenylcinnamides, the carbonyl oxygen is the thermodynamically most favorable protonation site and the added proton is initially localized on it. Upon collisional activation, the proton transfers from the carbonyl oxygen to the dissociative protonation site at the amide nitrogen atom or the α-carbon atom, leading to the formation of important reactive intermediates. When the amide nitrogen atom is protonated, the amide bond is facile to rupture to form ion/neutral complex 1, [RC(6)H(4)CH[double bond, length as m-dash]CHCO(+)/aniline]. Besides the dissociation of the complex, proton transfer reaction from the α-carbon atom to the nitrogen atom within the complex takes place, leading to the formation of protonated aniline. The presence of electron-withdrawing groups favored the proton transfer reaction, whereas electron-donating groups strongly favored the dissociation (aniline loss). When the proton transfers from the carbonyl oxygen to the α-carbon atom, the cleavage of the C(α)-CONHPh bond results in another ion/neutral complex 2, [PhNHCO(+)/RC(6)H(4)CH[double bond, length as m-dash]CH(2)]. However, in this case, electron-donating groups expedited the proton transfer reaction from the charged to the neutral partner to eliminate phenyl isocyanate. Besides the cleavage of the C(α)-CONHPh bond, intramolecular nucleophilic substitution (a nucleophilic attack of the nitrogen atom at the β-carbon) and stepwise proton transfer reactions (two 1,2-H shifts) also take place when the α-carbon atom is protonated, resulting in the loss of ketene and RC(6)H(5), respectively. In addition, the H/D exchanges between the external deuterium and the amide hydrogen, vinyl hydrogens and the hydrogens of the phenyl rings were discovered by D-labeling experiments. Density functional theory-based (DFT) calculations were performed to shed light on the mechanisms for these reactions.     

聚α烯烃光催化降解的机理研究

采用光催化微反应器对铜箔表面附着的聚α烯烃进行了光催化降解处理,利用X射线光电子能谱(XPS)、电子自旋共振谱(ESR)和傅里叶变换红外光谱(FTIR)等对光催化降解前后聚α烯烃的元素化学状态、自由基和官能团进行了检测,并探讨了光催化降解机理.结果表明,聚α烯烃光催化降解过程中发生了含氧基团的引入和CO_2脱附;参加降解反应的自由基主要为羟基自由基·OH,降解过程中—OH逐渐增多、C—H键逐渐减少;聚α烯烃光催化降解过程中,·OH进攻聚α烯烃是从取代反应开始的,首先取代的是末端的氢原子,然后是末端羟基向醛基和羧基的转变,最后是碳链断裂形成小分子有机物,这一过程持续进行,最终生成CO_2和H_2O等无机物.     

2-Aminoisobutyric acid in Co(II) and Co(II)/Ln(III) chemistry: homometallic and heterometallic clusters

The synthesis and magnetic properties of 13 new homo- and heterometallic Co(II) complexes containing the artificial amino acid 2-amino-isobutyric acid, aibH, are reported: [Co(II)(4)(aib)(3)(aibH)(3)(NO(3))](NO(3))(4)·2.8CH(3)OH·0.2H(2)O (1·2.8CH(3)OH·0.2H(2)O), {Na(2)[Co(II)(2)(aib)(2)(N(3))(4)(CH(3)OH)(4)]}(n) (2), [Co(II)(6)La(III)(aib)(6)(OH)(3)(NO(3))(2)(H(2)O)(4)(CH(3)CN)(2)]·0.5[La(NO(3))(6)]·0.75(ClO(4))·1.75(NO(3))·3.2CH(3)CN·5.9H(2)O (3·3.2CH(3)CN·5.9H(2)O), [Co(II)(6)Pr(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)CN)(6)]·[Pr(NO(3))(5)]·0.41[Pr(NO(3))(3)(ClO(4))(0.5)(H(2)O)(1.5)]·0.59[Co(NO(3))(3)(H(2)O)]·0.2(ClO(4))·0.25H(2)O (4·0.25H(2)O), [Co(II)(6)Nd(III)(aib)(6)(OH)(3)(NO(3))(2.8)(CH(3)OH)(4.7)(H(2)O)(1.5)]·2.7(ClO(4))·0.5(NO(3))·2.26CH(3)OH·0.24H(2)O (5·2.26CH(3)OH·0.24H(2)O), [Co(II)(6)Sm(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)CN)(6)]·[Sm(NO(3))(5)]·0.44[Sm(NO(3))(3)(ClO(4))(0.5)(H(2)O)(1.5)]·0.56[Co(NO(3))(3)(H(2)O)]·0.22(ClO(4))·0.3H(2)O (6·0.3H(2)O), [Co(II)(6)Eu(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)OH)(4.87)(H(2)O)(1.13)](ClO(4))(2.5)(NO(3))(0.5)·2.43CH(3)OH·0.92H(2)O (7·2.43CH(3)OH·0.92H(2)O), [Co(II)(6)Gd(III)(aib)(6)(OH)(3)(NO(3))(2.9)(CH(3)OH)(4.9)(H(2)O)(1.2)]·2.6(ClO(4))·0.5(NO(3))·2.58CH(3)OH·0.47H(2)O (8·2.58CH(3)OH·0.47H(2)O), [Co(II)(6)Tb(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)CN)(6)]·[Tb(NO(3))(5)]·0.034[Tb(NO(3))(3)(ClO(4))(0.5)(H(2)O)(0.5)]·0.656[Co(NO(3))(3)(H(2)O)]·0.343(ClO(4))·0.3H(2)O (9·0.3H(2)O), [Co(II)(6)Dy(III)(aib)(6)(OH)(3)(NO(3))(2.9)(CH(3)OH)(4.92)(H(2)O)(1.18)](ClO(4))(2.6)(NO(3))(0.5)·2.5CH(3)OH·0.5H(2)O (10·2.5CH(3)OH·0.5H(2)O), [Co(II)(6)Ho(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)CN)(6)]·0.27[Ho(NO(3))(3)(ClO(4))(0.35)(H(2)O)(0.15)]·0.656[Co(NO(3))(3)(H(2)O)]·0.171(ClO(4)) (11), [Co(II)(6)Er(III)(aib)(6)(OH)(4)(NO(3))(2)(CH(3)CN)(2.5)(H(2)O)(3.5)](ClO(4))(3)·CH(3)CN·0.75H(2)O (12·CH(3)CN·0.75H(2)O), and [Co(II)(6)Tm(III)(aib)(6)(OH)(3)(NO(3))(3)(H(2)O)(6)]·1.48(ClO(4))·1.52(NO(3))·3H(2)O (13·3H(2)O). Complex 1 describes a distorted tetrahedral metallic cluster, while complex 2 can be considered to be a 2-D coordination polymer. Complexes 3-13 can all be regarded as metallo-cryptand encapsulated lanthanides in which the central lanthanide ion is captivated within a [Co(II)(6)] trigonal prism. dc and ac magnetic susceptibility studies have been carried out in the 2-300 K range for complexes 1, 3, 5, 7, 8, 10, 12, and 13, revealing the possibility of single molecule magnetism behavior for complex 10.     

CH(A^2Δ)自由基被醇类分子猝灭动力学的温度效应研究

用266nm激光光解CHBr3产生CH自由基, 利用精密控温仪控制反应温度, 测定CH(A→X)荧光的时间分辨信号, 测量了290K至653K范围内CH(A)被乙醇、丙醇、丁醇猝灭的速率常数, 利用修正的碰撞配合物模型, 定性解释了在多极吸引势与活化势垒的双重影响下, 猝灭截面与温度间的关系。     

Supramolecular silanol chemistry in the gas phase. Topological (AIM) and population (NBO) analyses of hydrogen-bonded complexes between H3SiOH and selected O- and N-acceptor molecules

Hydrogen bonding of the type SiO-H...A (A = O, N) has been studied in the gas phase for simple H3SiOH.acceptor complexes with the acceptor molecules being O(H)SiH3, OH2, O(H)CH3, O(CH3)2, O(CH3)SiH3, O(SiH3)2, NH3, N(CH3)H2, N(CH3)2H, N(CH3)3, N(CH3)2C6H5, and NC5H5, respectively, at the B3LYP/6-311+(2d,p) level of theory, using Bader's atoms in molecules (AIM) and Weinhold's natural bond orbital (NBO) methodology. For all complexes (except H3SiOH.N(CH3)2C6H5) the complex energy Eadd. is a good estimate for the hydrogen bond energy EHB, which is generally higher in N-acceptor complexes (-5.52 to -7.17 kcal mol-1) than in O-acceptor complexes (-2.09 to -5.06 kcal mol-1). In case of H3SiOH.N(CH3)2C6H5, EHB and Eadd. differ by the energy associated with the loss of n(N)-->pi conjugation in N(CH3)2C6H5 upon complex formation. EHB shows no correlation with O...A distances and the red shifts Deltanu(OH) of the OH-stretching vibrations when different acceptors are compared, although both parameters are commonly used to estimate the strength of the hydrogen bond from spectroscopic and diffraction data. A good linear correlation of the hydrogen bond energy EHB has been established with parameters derived from the AIM and NBO analyses, namely, the electron densities rho(HA) and rho(OH) at the H...A and O-H bond critical points (BCPs) and the NLMO bond orders BONLMO(HA) of the H...A bonds of the H3SiOH.acceptor complexes as well as the change of natural charges DeltaqNPA(O) at the O-donor atom upon H3SiOH.acceptor complex formation. Hydrogen bonding of the type SiO-H...A (A = O, N) has been also studied in the related cyclic multiple H3SiOH.acceptor complexes (H3SiOH)3, (H3SiOH)2.NC5H5, and (H3SiOH)4, respectively, at the same level of theory. Cooperative hydrogen bonding is evident for all cyclic multiple H3SiOH.acceptor complexes, whereby the strongest concomitant strengthening of the hydrogen bonds is observed for (H3SiOH)4 and (H3SiOH)2.NC5H5.     

Synthesis and Crystal Structure of a New Complex Zn(Ⅱ)L_2·2CH_3OH(H_2L = 4-Chloro-2-(2,3-dihydro-1H-benzoimidazol-2-yl)-phenol)

A new complex Zn(Ⅱ)L2·2CH3OH(H2L = 4-chloro-2-(2,3-dihydro-1H-ben-zoimi-dazol-2-yl)-phenol) has been prepared and characterized by single-crystal X-ray diffraction analysis and elemental analysis.The crystal is of triclinic system,space group P1 with a = 9.2905(10),b = 10.3555(13),c = 14.9590(14) ,α = 101.0340(10),β = 101.261(2),γ = 99.1660(10)o,V = 1356.1(3) 3,Z = 2,C28H24Cl2N4O4Zn,Mr = 616.78,Dc = 1.510 g/cm3,μ = 1.145 mm·1,F(000) = 632,the final R = 0.0379 and wR = 0.0830 for 3606 observed reflections with I 2σ(I).The Zn(Ⅱ) atom presents a distorted square pyramidal coordination involving two H2L ligands.The hydrogen bonds and π···π stacking interactions extend the complex into a two-dimensional framework.     

Photodissociation dynamics of benzyl alcohol at 193 nm

Photodissociation dynamics of benzyl alcohol, C(6)H(5)CH(2)OH and C(6)H(5)CD(2)OH, in a molecular beam was investigated at 193 nm using multimass ion imaging techniques. Four dissociation channels were observed, including OH elimination and H(2)O elimination from the ground electronic state, H atom elimination (from OH functional group), and CH(2)OH elimination from the triplet state. The dissociation rate on the ground state was found to be 7.7 × 10(6) s(-1). Comparison to the potential energy surfaces from ab initio calculations, dissociation rate, and branching ratio from Rice-Ramsperger-Kassel-Marcus calculations were made.