Application of symplectic algorithms to QCT calculation:H+H_2 system

The basic theory of symplectic algorithm was introduced. A comparison between Runge-Kutta method and symplectic integration method was preformed in the simulation of the long time behavior of H + H2 system on BKMP potential energy surface. Our results reveal a dis-sipative behavior in the integral of ordinary differential equation by the fourth order Runge-Kutta method, which causes incorrect simulation results in QCT calculations. However, when the symplectic integration method is applied, the dissipative behavior is not found in the same system. When the initial state is the same, the energy deviation of fourth order symplectic integral method is almost one percent of that of fourth order Runge-Kutta method in a 60000-step simulation, and that of sixth order symplectic integral method is much less. These results show that the symplectic integral methods are always the better choice in the integral calculation of the long time behavior in maintaining energy conservation.     

Kinetics of energy transfer processes in C-phycocyanin complexes

The antenna system of algae for photosynthesis is a functional entity composed of various phycobiliproteins and the linker polypeptides. Up to now, high-resolution crystal structure data have been available only for the isolated phycobiliproteins. To have an understanding of the functional connection between different phycobiliproteins, it is necessary to study the complexes composed of different phycobiliproteins. The energy transfer processes in C-phycocyanin complexes were studied through computer simulation because it is difficult to be studied by conventional experimental methods. The main pathways of energy flow and the dynamic property of the energy transfer were obtained. A fast transfer process between two neighboring disks was observed through analyzing the distribution curves of excitation energy over time. According to the definition of the time constants for energy transfer in time-resolved spectrum techniques, for a complex with three C-phycoeyanin hexamer disks, a fluorescence-rising comp     

Detection of OH Radical in the Photodissociation of p-Aminobenzoic Acid at 266 nm

Photodissociation of p-aminobenzoic acid at 266 nm was investigated by probing the nascent OH photoproduct employing the laser-induced fluorescence technique. It was found that the nascent OH radical was vibrationally cold and its rotational state distribution conformed to be a Boltzmann behavior, characterized by a rotational temperature of 1040±110 K. The rotational energy of OH was determined to be 8.78±0.84 kJ/mol. Between the two spinorbit states of OH, ^2Ⅱ3/2 and ^2Ⅱ1/2, the former was found to be preferentially populated. The distribution of the II（A＇） state for the A-doublet was dominant. Finally, a probable mechanism for the formation of OH produced from the photodissociation of p-aminobenzoic acid is discussed.     

UV Photodissociation Dynamics of Nitric Acid： The Hydroxyl Elimination Channel

Sliced velocity mapping ion imaging technique was employed to investigate the dynamics of the hydroxyl elimination channel in the photodissociaiton of nitric acid in the ultraviolet region. The OH product was detected by （2＋1） resonance enhanced multiphoton ionization via the D^2∑^- electronic state. The total kinetic energy spectra of the OH＋NO2 channel from the photolysis of HONO2 show that both ：NO2（X2A1） and NO2（A2B2） channels are present, suggesting that both 1^1A″ and 2^1A″ excited electronic states of HONO2 are involved in the excitation. The parallel angular distributions suggest that the dissociation of the nitric acid is a fast process in comparison with the rotational period of the HNO3 molecule. The anisotropy parameter β for the hydroxyl elimination channel is found to be dependent on the OH product rotational state as well as the photolysis energy.     

The effects of ultrasound frequency and power on the activation energy in Si-KOH reaction system

The activation energy is the minimum amount of energy required to initiate a reaction. It is one of the important indexes for appraising a reaction. The chemical reaction rate is closely related to the value of activation energy, and reducing activation energy is propitious to promoting a chemical reaction. In the present paper, the relationship between the activation energy in Si-KOH reaction system and the ultrasound frequency and power has been discussed for the first time. The range of ultrasound frequency and power is 40-100kHz （interval by 20kHz） and 10-50W （interval by 10W）, respectively. The experimental clata indicate that the activation energy decreases with the increasing ultrasound power. Comparing with the activation energy without ultrasound irradiation, the results in our paper indicate that ultrasound irradiation could reduce the activation energy in Si-KOH reaction system and increase the reaction rate.     

Time-dependent treatment of intramolecular energy transfer for HeICl complex

The time-dependent golden wave packet method has been used for calculating the decay widths of vibrational predissociation for HeICl complex in the B state with total angular momentum J=0. This is a good example of intramolecular energy transfer. We examine the dependence of the final rotational distribution (partial decay width) of ICl fragment on the stretching excitation. It is found that computed final rotational distributions are weakly dependent on the vibrational level being excited. Unlike the smoothly varying rotational distribution for lower initial vibrational levels, for higher initial vibrational levels the rotational distribution indicates the very pronounced oscillatory structure. The analysis of the rotational distribution as a function of propagation time reveals the predominant role of the final states interaction in determining the final rotational distribution.     

The Energy Transfer Processes between Carotenoid and Chlorophyll Regulated by Electron Exchange Mechanism

Phycobilisomes, carotenoids and chlorophylls are the major pigments for photosynthesis of alga1. But the exact mechanism for the excitation energy transfer between carotenoids and chlorophylls is not clear yet. Compared with the energy transfer process in the phycobilisome to photosystems, the overlap integral of emission spectra of carotenoid with the absorption spectra of the chlorophyll is small and the quantum yield of the carotenoid fluorescence is weak. This fact indicated that the me…     

Artificial stepwise light harvesting system in water constructed by quadruple hydrogen bonding supramolecular polymeric nanoparticles

Stepwise energy transfer is ubiquitous in natural photosynthesis, which greatly promotes the widespread use of solar energy. Herein, we constructed a supramolecular light harvesting system based on sequential energy transfer through the hierarchical self-assembly of M, which contains a cyanostilbene core flanked by two ureidopyrimidinone motifs, endowing itself with both aggregation-induced emission behavior and quadruple hydrogen bonding ability. The monomer M can self-assemble into hydrogen bo...     

Quasi-classical trajectory approach to the stereo-dynamics of the reaction F+HO→HF+O

Quasi-classical trajectory (QCT) calculations are employed for the reaction F + HO(0,0)→HF + O based on the adiabatic potential energy surface (PES) of the ground 3A″triplet state. The average rotational alignment factor P2(j′·k) as a function of collision energy and the four polarization dependent generalized differential cross sections have been calculated in the center-of-mass (CM) frame, separately. The distribution P(θr) of the angle between k and j′, the distribution P(θr) of dihedral angle denoting k-k′-j′ correlation, and the angular distribution P(θr, Φr) of product rotational vectors in the form of polar plots are calculated as well. The effect of Heavy-Light-Heavy (HLH) mass combination and atom F's relatively strong absorbability to charges on the alignment and the orientation of product molecule HF rotational angular momentum vectors j′ is revealed.     

ICAR ATRP of acrylonitrile utilizing a moderate temperature radical initiator

Initiators for continuous activator regeneration atom transfer radical polymerization （ICAR ATRP） of acrylonitrile was first conducted at various ambient temperatures （30-45 ℃）. The key to success is ascribed to the usage of an appropriate low temperature radical initiator （2,2＇-azobis（2,4-dimethylvaleronitrile）） and a high reactivity catalytic system （CuBr2/Me6TREN）. The molar ratio of Cu catalyst tO AN as low as 1：20000 wa.s used to prepare well-defined polyacrylonitrile with controlled molecular weight and a narrow polydispersity index range of 1.08-1.30, while the monomer conversion was up to ca. 98%. The apparent activation energy of the polymerization was calculated to be 128.45 kJ/mol, suggesting that the polymerization strongly depended on reaction temperature. The very high chain-end functionality of the resultant polymer was confirmed by ^1H-NMR and GPC analyses as well as chain extension reaction.     

Synthesis, Crystal Structure, Physical Properties, and Application of a Series of Functional Dibenzo[d,f][1,3]dioxepine Derivatives

The twisted aromatics, functional dibenzo[d,f][1,3]dioxepine derivatives were synthesized in high yields from reactions of 5,5＇-dibromo-2,2＇-biphenol with corresponding ketal or ketone compounds under acid catalysis. The structures of these compounds were characterized by ^1H NMR, elemental analysis, UV-Vis absorption spectrum and X-ray diffraction analysis. The conformation of O--C--O bridged biphenyl derivatives with varied substitute groups on 6,6＇-position was studied by X-ray crystallography and force-field simulation. The result of calculations by UNIVERSAL 1.02 force field in Cerius2 package（4.6） indicates that dibenzo[d,f][1,3]dioxepine derivatives show twisted conformations and the twisted angle between the phenyl rings is about 40°, which is accordant with the result from crystal structure determination, though the obtained angles in the crystal of dibenzo[d,f][1,3]dioxepine derivatives with the varied substitute groups on 6,6＇-position are shown to be slightly shifted to 40° owing to intermolecular interactions in crystal stacking. DSC studies exhibit that the substitute groups on 6,6＇-position can induce a large variation of endothermic peaks ranging from 80 to 135 ℃. The conjugated polymers based on dibenzo[d,f][1,3]dioxepine derivatives, which have ultraviolet emitting with a quantum efficiency of 10%, were obtained by Yamamoto coupling.     

THE THEORETICAL STUDIES OF PRODUCT ALIGNMENT OF THE REACTIONS OF Na,F WITH CH_3I

The NaI and IF product rotational alignment of the reactionsof Na,F+CH_3I has been theoretically studied in a LEPS PES.Theproduct alignment versus the relative translational energy of the reactantshas been obtained.     

两个新颖的联环十二烷衍生物的合成及结构表征

2-（2＇-Oxo-3＇-oximidocyclododecyl） cyclododecanone （1） and 2-（1＇-hydroxylcyclododecyl） cyclododecanone （2） were synthesized and characterized. The conformation analysis was carried out based on the NMR, molecular mechanics calculation and X-ray diffraction. The conformation of two cyclododecyl moieties of both 1 and 2 was found to be the [3333]-2-one or [3333] square conformation both in the crystal state and the solution. The dihedral angle between carbonyl and the oxime double bond of the ring B is 180°in the crystal of 1. The protons or hydroxyl group of carbon atoms to link the two cyclododecyl moieties of 1 and 2 constitute dihedral angles of 174°in the crystal, and 175°in the solution, and the C-C 6 bond between two cyclododecyl moieties can not freely rotate in the solid state and the solution. In addition, compound 2 was the first example of a-comer-anti-monosubstituted cyclododecanone. synthesis     

8-羟基喹啉单体及二聚体质子转移反应的理论研究

Density functional theory （DFT） of quantum chemistry method was employed to investigate proton transfer reactions of 8-hydroxyquinoline （8-HQ） monomers and dimers. By studying the potential energy curves of the isomerization, the most possible reaction pathway was found. The total energy of 8-hydroxyquinoline was lower than that of quinolin-8（1H）-one, whereas the order was reversed in dimers. The findings explained the contrary experimental phenomena. The minimum reaction barrier of intramolecular proton transfer was 47.3 kJ/mol while that in dimer was only 25.7 kJ/mol. Hence it is obvious that proton transfer reactions of 8-HQ monomer have a considerable rate but it is easier to proceed for 8-HQ dimer than monomers. It implied that the hydrogen bond played an important role in depressing the activation energy of reaction. The mechanism of the tautomerization was discussed on the basis of theoretical results.     

两种吩噻嗪衍生物的合成，光学性质及其电化学性质

The synthesis, luminescence and electrochemical properties of two novel phenothiazine derivatives were presented, which exhibit good one-photon fluorescence emission. The quantum yields and solvent effects of them were studied in detail. Compound 3,7-bis（2-4＇-imidazolylbenzylidenehydrazonoethyl）-（0-ethylphenothiazine） （5） was used as an effective initiator, of which two-photon fluorescence spectra were investigated under 800 nm fs laser pulse and the measured two-photon absorption cross-section was 18 × 10^-50 cm^4·s per photon. Two-photon initiated polymerization microfabrication experiments were carried out. X-ray diffraction analyses revealed that the shape of the compound 3,7-bis（2-pyrid-4＇-ylmethylidenehydrazonoethyl）-（0-ethylphenothiazine） （4） looks like a butterfly with nearly planar wings. The dihedral angle of the two benzene rings is 37.6° and there is an obvious π-π stacking interaction between the molecules in the crystal.     

Trans-cis photoisomerization of azobenzene by n →π^＊ excitation： A semiclassical dynamics study

A realistic dynamics simulation study is reported for the trans-cis photoisomerization of azobenzene triggered by the n →π^＊ excitation and the results show that the formation ofcis isomer follows the rotational motion around the N=N bond. The simulation find that the CNN bond angle bending vibrations also play a significant role in the vibronic coupling between the HOMO and LUMO, which essentially leads a nonadiabatic transition of the molecule to the electronic ground state.     

A theoretical study on the water-mediated asynchronous addition between urea and formaldehyde

The reaction between urea and formaldehyde in water solution was theoretically investigated by using B3LYP and MP2 methods.It was found that the addition of the nitrogen atom in urea to the carbonyl group in formaldehyde precedes the proton transfer and the proton migration from water to the carbonyl group occurs before the proton abstraction from the nitrogen.With one or two water molecules involved in the TS.the activation energy barrier is lowered compared to the TS of the mechanism with no water participation.The energy change along the reaction coordinate clearly shows that a zwitterionic-like intermediate does not exist on the PES.The reaction between urea and formaldehyde occurs in a concerted mechanism but with asynchronous characters.This is different from the stepwise mechanism recently found for the amination reactions of formaldehyde.     

Two-photon Dissociation Study of Carbon Disulfide in Acetonitrile at 266 nm

Using laser flash photolysis/transient absorption technique for the study of two photon photodissociation of carbon disulfide in acetonitrile solution at 266 nm, the transient UV-Vis absorption spectrum of Rydberg state CS2 （6sσg） within 240-370 nm and subsequent dissociation product CS （α^3П） with the maximum absorption at 260 nm were directly observed. The lifetime of CS （α^3П） in the nitrogen and oxygen saturated solution is also studied in our experiment.     

Charge transfer across the water/nitrobenzene interface by three-electrode system

A droplet of aqueous solution containing a certain molar ratio of redox couple is first attached onto a platinum electrode surface, then the resulting drop electrode is immersed into the organic solution containing very hydrophobic electrolyte. Combined with reference and counter electrodes, a classical three-electrode system has been constructed. Ion transfer (IT) and electron transfer (ET) are investigated systematically using three-electrode voltammetry. Potassium ion transfer and electron transfer between potassium ferricyanide in the aqueous phase and ferrocene in nitrobenzene are observed with potassium ferricyanide/potassium ferrocyanide as the redox couple. Meanwhile, the transfer reactions of lithium, sodium, potassium, proton and ammonium ions are obtained with ferric sulfate/ferrous sulfate as the redox couple. The formal transfer potentials and the standard Gibbs transfer energy of these ions are evaluated and consistent with the results obtained by a four-electrode system and other methods.     

Thermodynamics for nonequilibrium solvation and numerical evaluation of solvent reorganization energy

This work presents a thermodynamic method for treating nonequilibrium solvation. By imposing an extra electric field onto the nonequilibrium solvation system, a virtual constrained equilibrium state is prepared. In this way, the free energy difference between the real nonequilibrium state and the con-strained equilibrium one is simply the potential energy of the nonequilibrium polarization in the extra electronic field, according to thermodynamics. Further, new expressions of nonequilibrium solvation energy and solvent reorganization energy have been formulated. Analysis shows that the present formulations will give a value of reorganization energy about one half of the traditional Marcus theory in polar solvents, thus the explanation on why the traditional theory tends to overestimate this quantity has been found out. For the purpose of numerical determination of solvent reorganization energy, we have modified Gamess program on the basis of dielectric polarizable continuum model. Applying the procedure to the well-investigated intramolecular electron transfer in biphenyl-androstane-naphthyl and biphenyl-androstane-phenanthryl systems, the numerical results of solvent reorganization energy have been found to be in good agreement with the experimental fittings.