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1.
An ab initio calculation of electron transfer reactivity of Mn2+OH2/Mn3+OH2 redox system, in gas and in solution, has been made in this paper. The detailed geometry optimization and the scanning of the potential energy surfaces have been carried out at UMP2 (full)/6-311+G* level. The relevant energy quantities (such as the activation energy and the binding energy) are calculated at different levels of theory (HF, MP2, MP3, MP4 and QCISD and corresponding spin-projection PUHF, PMP2 and PMP3) with the same basis set (6-311+G*). Both all-electrons and valence electrons have been correlated in energy calculations. 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 obtained using both a classical sphere approximation scheme and a novel scheme. The relevant kinetic parameters are obtained at different ab initio levels in terms of the new model. The contact-distance dependence of these parameters and the applicability of the presented models are also discussed.  相似文献   

2.
A new type of catalyst from supporting C60 on MoO3 and Al2O3 has been prepared. The effect of different order of impregnation and calcination atmosphere on catalyst are investigated by the solution test in toluene, UV-VIS spectroscopy and temperature programmed reduction (TPR). The results show that when the catalyst was prepared by supporting MoO3 on C60/Al2O3 and calcined in N2, there is a stronger interaction between C60, MoO3 and Al2O3, but when supporting C60 on MoO3/Al2O3, the interaction is relatively weak. We consider that in the former method a new complex, Mo–C60–O–Al, is formed.  相似文献   

3.
The structures and properties of the O2+O2 electron transfer system in the quartet state, both in the gaseous phase and in solution, were studied at the UMP2(full)/6-311+G* basis set level for the five selected coupling structures: two T-type, collinear, parallel, and crossing. The stabilities of these encounter complexes were compared. The activation barriers, coupling matrix elements, and the electron transfer rate at two theoretical levels (semiclassical and quantum mechanical) were also calculated for the quartet state, and the effect of the solvent medium evaluated at the self-consistent reaction field level. Results indicate that the structures and properties of the encounter complexes directly affect the mechanism and rate of the electron transfer reaction, the contact distances for this O2…O2 were generally large (3 Å), the interaction between the donor and the acceptor was weak, and the structures are floppy. The electronic transmission factor for the reacting system, O2+O2, was less than unity (ca. 001–0.6), thus the electron transfer reaction was non-adiabatic in nature. Analysis of the dependence of relevant kinetic parameters on various influencing factors showed that the effect of the solvent medium on the coupling matrix element was small, but that on the electron transfer rate was very large, and the gaseous phase results for the molecular geometrical parameters and their contributions can directly transfer to solution. Among the five selected transition state structures, the electron transfer was more likely to take place via the T-type and the P-type structures, the rate values from two theoretical levels were in good agreement with each other and were also very close to the experimental findings. If the various anharmonic vibrational contributions, the effect of the solvent molecular electronic structures and the interaction between the reacting species and the solvent medium are taken into account, the results can be improved.  相似文献   

4.
Possibility of encapsulations of metallofullerenes inside single-walled boron nitride nanotubes (BNNTs) is studied by using first-principles calculations. We find that both La@C82 and La2@C80 can be exothermically encapsulated inside the (17, 0) and (14, 7) BNNTs. The minimum diameters of exothermically encapsulating both La@C82 and La2@C80 inside BNNTs are predicated to be about 13.4 Å.  相似文献   

5.
Ampoule reactions of C70 with n- and i-C3F7I were carried out at 250-310 °C. Two step HPLC separations allowed the isolation of several C70(n-C3F7)4-8 and C70(i-C3F7)4 compounds. Crystal and molecular structures of C70(n-C3F7)8-V, C70(n-C3F7)6O, C70(n-C3F7)4, and three isomers of C70(i-C3F7)4 have been determined by X-ray crystallography using synchrotron radiation. Molecular structures of the new compounds were compared with the known examples and discussed in terms of addition patterns and relative energies of their formation.  相似文献   

6.
One isomer of C60(i-C3F7)8, three isomers of C60(i-C3F7)6, and the first mixed perfluoroalkylated fullerene, C60(CF3)2(i-C3F7)2, have been isolated by HPLC from a mixture prepared by reaction of C60 with heptafluoroisopropyl iodide in a glass ampoule at 260-290 °C. The molecular structures of the four new compounds have been determined by means of X-ray single crystal diffraction partially also by use of synchrotron radiation. Theoretical calculations at the DFT level of theory have been employed to rationalize the energetics of isomers and of C60-Rf binding.  相似文献   

7.
A theory for charge transfer between the electrode and the donor/acceptor molecule coupled through a DNA bridge in solution is developed. We explore the crossover between the coherent tunneling and the incoherent sequential transfer regimes by varying the electrode potential and discuss the effects of single-base mismatches in DNA duplex in both regimes. In the former regime a single-base mismatch in DNA duplex causes a reduction in the charge transfer rate simply by decreasing the electron tunneling matrix element, however, in the latter regime the effects are rather complicated.  相似文献   

8.
In this opinion paper, we discuss the charge transfer at biotic/abiotic interfaces in man-made and biological electrochemical systems. Specifically, we will first introduce the heterogeneous charge transfer at the bioelectrode interface, followed by the intramolecular change transfer in peptide and protein structures, and finally discuss the extracellular charge transfer in electrogenic microorganisms. In addition to discussion of charge transfer mechanisms and synthetic structures/scaffolds required for it, a particular focus will be given to novel experimental designs that are able to bring new concepts and boost mechanism understanding and applications development. There are also discussions on the combination of modern computational techniques and experimental characterizations.  相似文献   

9.
Sub-picosecond transient absorption study has been employed to study the electron transfer kinetics in the dye-sensitized TiO2 films used in commercial photovoltaic devices. The electron injection in these dye sensitized films occurs on an ultrafast time scale with two components, 150 fs and 1·2 ps.  相似文献   

10.
The performance of Fourier transform infrared spectroscopy (FT-IR) detection coupled to high-performance liquid chromatography for the analysis of C60 and C70 fullerenes was investigated. The isocratic separation method involved an octadecylsilane (ODS) column and an acetonitrile–toluene (1:1) mobile phase. The hyphenated system was designed with a split valve to control eluent volume leading to the FT-IR detector; this allowed for additional coupling of the liquid chromatograph to ultraviolet–visible detection. On-line FT-IR spectra of C60 and C70 were matched with standard off-line FT-IR spectra from the literature. In addition, with band chromatograms individual fullerenes can be identified using FT-IR active modes known specifically for each fullerene. Few changes to a pre-existing HPLC–UV method were necessary for the HPLC–FT-IR method, and there was no need for fraction collection to identify the fullerenes C60 and C70.  相似文献   

11.
Room temperature ionic liquid [bmim]PF6 was used to immobilize a bimetallic catalytic system for H2O2-based dihydroxylation of alkenes. Osmium tetroxide was used as the substrate-selective catalyst with either VO(acac)2 or MeReO3 as co-catalyst. The latter serve as an electron transfer mediator (ETM) and activates H2O2. For an increased efficiency N-methylmorpholine is required as an additional ETM in most cases. A range of alkenes were dihydroxylated using this robust bimetallic system and it was demonstrated that for some of the alkenes the catalytic system can be recycled and used up to five times.  相似文献   

12.
孙健  刘扬  陈德文  张启元 《物理化学学报》1999,15(12):1088-1091
采用ESR技术对甲基紫精(MV2 )在三乙胺与C60的电子转移反应中的催化作用进行了研究.反应体系无MV2 存在时,三乙胺与C60并不发生电子转移反应,得不到电荷的分离态;在MV2 存在的条件下,由三乙胺向C60分子的电子转移得以实现,并检测到活泼中间体MV ·及电荷分离态C-·60,MV2  实质上起到催化剂的作用.  相似文献   

13.
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.  相似文献   

14.
Epitaxial growth and electron doping of 12CaO·7Al2O3 (C12A7) and 12SrO·7Al2O3 (S12A7) are reported. The C12A7 films were prepared on Y3Al5O12 (YAG) single-crystal substrates by pulsed laser deposition at room temperature and subsequent thermal crystallization. X-ray diffraction patterns revealed the films were grown epitaxially with the orientation relationship of (001)[100] C12A7 || (001)[100] YAG. For S12A7, pseudo-homoepitaxial growth was attained on the C12A7 epitaxial layer. Upon electron doping, metallic conduction was achieved in the C12A7 film and the S12A7/C12A7 double-layered films. Analyses of optical absorption spectra for the S12A7/C12A7 films provided the densities of free electrons in each layer separately. Hall measurements exhibited larger electron mobility in the S12A7/C12A7 film than those in C12A7 and S12A7 films, suggesting free electrons may be accumulated at the S12A7/C12A7 interface due presumably to a discontinuity of the cage conduction bands.  相似文献   

15.
Ru(bpz)32+ (bpz = 2,2′-bipyrazine) has six peripheral uncoordinated nitrogen atoms potentially available for protonation in presence of acids. The emission from *Ru(bpz)32+ is efficiently quenched by organic acids and the observed quenching rate constants are explained in terms of proton transfer from acids to *Ru(bpz)32+. The absorption and emission intensity of Ru(bpz)32+ increases with increasing concentration of carboxylate ion suggesting the complex formation between the two reactants in the ground state. From these studies, the formation constant (Kf) have been evaluated by Benesi–Hildebrand method. The Kf values indicate that generally the ion pair association constants estimated from absorption and emission techniques are comparable and these values are sensitive to the structure of the carboxylate ions.  相似文献   

16.
The TCNX ligands TCNE (tetracyanoethene) and TCNQ (7,7,8,8-tetracyano-p-quinodimethane) react instantaneously with (C5R5)2(CO)2Ti, R=H or Me, to yield highly air-sensitive mononuclear complexes (C5R5)2(CO)Ti(TCNX) of which the soluble species (R=Me) were characterized also in the oxidized and reduced forms through cyclic voltammetry, EPR, IR and UV-vis spectroelectrochemistry. While oxidation at rather low potentials yields labile carbonyltitanium(IV) species of the TCNX ligands, the reduction occurs stepwise at unusually negative potentials, first on the ligand (to yield coordinated TCNX2−) and then on the metal (to form TiII). For the neutral complexes (C5R5)2(CO)Ti2+q(TCNXq) the results support a rather large amount of charge transfer 1<q<2 from the metal to the acceptors TCNX. Evidence for the previously formulated {(μ-TCNE2−)[(C5H5)2TiIV(CO)]2}(TCNE2−) could not be found. The complexes (C5R5)2(CO)Ti(TCNE) are compared with related compounds (C5R5)2BrV(TCNE), (C6R6)(CO)2Cr(TCNE) and (C5R5)(CO)2Mn(TCNE).  相似文献   

17.
Electron transfer is a common characteristic in fullerene complexes and brings about an optoelectronic effect in a polymer-C60 composite and superconductivity in alkali-metal doped C60. This paper reports that the concept of self-trapping of the transferred electron in C60 can explain the main features of photoinduced electron transfer in a polymer-CC60 composite and electron pairing in alkali-metal doped C60.  相似文献   

18.
We report on the crystallographic structure of the layered perovskite iridate Sr3Ir2O7, investigated using transmission electron microscopy. The space group was found to be Bbcb (, No. 68 in the International Tables for Crystallography) at 315 K. A very fine twin structure with 90° rotation with respect to the c-axis was observed. The crystal structure at temperatures lower than 285 K, where a phase transition from paramagnetism to weak ferromagnetism is known to occur, was also examined. There was no difference in the extinction rule for the diffraction patterns between the two phases. We conclude that there is no change in the space group for this magnetic transition. There still remains the possibility of a change in the rotation angle of IrO6 octahedrons and a corresponding change in the interatomic distance between Ir and O, though.  相似文献   

19.
Thermodynamic properties of binary systems of C60 with 1,2- and 1,3-dibromobenzenes have been studied by means of differential scanning calorimetry (DSC). Solid solvates with the compositions C603(1,2-C6H4Br2); C602(1,3-C6H4Br2) and C600.6(1,3-C6H4Br2) have been found. The solvates have been characterised by their enthalpies and temperatures of incongruent melting transition and in part by X-ray powder data. It has been shown that positional isomers 1,2- and 1,3- of the substituted benzenes formed two series of “typical” phase diagrams. Solubility behaviour of C60 in positional isomers has been discussed.  相似文献   

20.
A quaternary phase, Ba3La3Mn2W3O18, was synthesized in reduced atmosphere (5% H2/Ar) at 1200 °C and characterized by using powder X-ray diffraction, electron diffraction and high resolution TEM. Ba3La3Mn2W3O18 crystallizes in rhombohedral space group with the cell parameters, and , and can be attributed to the n=6 member in the B-site deficient perovskite family, AnBn−1O3n. The structure can be described as close-packed [La/BaO3] arrays in the sequence of (hcccch)3, wherein the B-site cations, W and Mn, occupy five octahedral layers in every six octahedral layers, which leave a vacant octahedral layers separating the 5-layer perovskite blocks. The B-cation layers in the perovskite block alternate along the c-axis in a sequence of W6+-Mn2+-W5+-Mn2+-W6+. The bond valence calculation and optical reflection spectrum confirm the presence of W5+. This compound behaves paramagnetically in wide temperature range and weak antiferromagnetic interaction only occurs at low temperatures.  相似文献   

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