共查询到20条相似文献,搜索用时 46 毫秒
1.
Gold(I) thiolate compounds (i.e. AuI-SR) are important precursors for the synthesis of atomically precise Aun(SR)m nanoclusters. However, the nature of the AuI-SR precursor remains elusive. Here, we report that the Au10(TBBT)10 complex is a universal precursor for the synthesis of Aun(TBBT)m nanoclusters (where TBBT=4-tertbutylbenzenethiol/thiolate). Interestingly, the Au10(TBBT)10 complex is also found to be re-generated through extended etching of the Aun(SR)m nanoclusters with excess of TBBT thiol and O2. The formation of well-defined Au10(TBBT)10 complex, instead of polymeric AuI-SR, is attributed to the bulkiness of the TBBT thiol. Through 1D and 2D NMR characterization, the structure of Au10(TBBT)10 is correlated with the previously reported X-ray structure, which contains two inter-penetrated Au5(TBBT)5 rings. The photophysical property of Au10(TBBT)10 complex is further probed by femtosecond transient absorption spectroscopy. The accessibility of the precise Au10(TBBT)10 precursor improves the efficiency of the synthesis of the Aun(TBBT)m nanoclusters and is expected to further facilitate excellent control and understanding of the reaction mechanisms of nanocluster synthesis. 相似文献
2.
Structures and thermochemistry of methyl ethyl sulfide and its hydroperoxides: HOOCH2SCH2CH3, CH3SCH(OOH)CH3, CH3SCH2CH2OOH,and radicals 下载免费PDF全文
Hydroperoxides and the corresponding peroxy radicals are important intermediates during the partial oxidation of methyl ethyl sulfide (CH3SCH2CH3) in both atmospheric chemistry and in combustion. Structural parameters, internal rotor potentials, bond dissociation energies, and thermochemical properties (ΔHfo, So and Cp(T)) of 3 corresponding hydroperoxides CH2(OOH)SCH2CH3, CH3SCH(OOH)CH3, CH3SCH2CH2OOH of methyl ethyl sulfides, and the radicals formed via loss of a hydrogen atom are important to understanding the oxidation reactions of MES. The lowest energy molecular structures were identified using the density functional B3LYP/6‐311G(2d,d,p) level of theory. Standard enthalpies of formation (ΔHfo298) for the radicals and their parent molecules were calculated using the density functional B3LYP/6‐31G(d,p), B3LYP/6‐31 + G(2d,p), and the composite CBS‐QB3 ab initio methods. Isodesmic reactions were used to determine ?Hfo values. Internal rotation potential energy diagrams and rotation barriers were investigated using the B3LYP/6‐31G(d,p) level theory. Contributions for So298 and Cp(T) were calculated using the rigid rotor harmonic oscillator approximation based on the structures and vibrational frequencies obtained by the density functional calculations, with contributions from torsion frequencies replaced by internal rotor contributions. The recommended values for enthalpies of formation of the most stable conformers of CH3SCH2CH2, CH2(OOH)SCH2CH3, CH3SCH(OOH)CH3, and CH3SCH2CH2OOH are ?14.0, ?33.0, ?37.2, and ?32.7 kcal/mol, respectively. Group additivity values were developed for estimating properties of structurally similar and larger sulfur‐containing peroxides. Groups for use in group additivity estimation of sulfur peroxide thermochemical properties were developed. 相似文献
3.
The 2ν3 overtone (A1, E) and the ν1 + ν3 (E) combination bands of the oblate symmetric top 14NF3 were studied by FTIR spectroscopy with a resolution of 2.5 × 10−3 cm−1. Nearly 500 lines up to Kmax/Jmax = 30/43 were observed for the weak A1 component reaching the v3 = 20 substate (1803.1302 cm−1), the majority of which corresponded to reinforced K = 3p-type transitions. For the strong E component reaching the v3 = 2±2 substate (1810.4239 cm−1), about 3550 transitions were assigned up to Kmax/Jmax = 65/69, favoring a clear observation of the ℓ(4, −2) and ℓ(4, 4) splittings within the kℓ = −2 and +4 sublevels, respectively. The two v3 = 2 substates are linked by the ℓ(2, 2)- and ℓ(2, −1)-type interactions, providing severe crossings, respectively, at K′ = 6 and near K′ = 24 on the v3 = 2+2 side. A model working in the D-reduction and including all these ℓ-type interactions could reproduce together 3695 nonzero weighted experimental data (NZW) through 33 free parameters with a standard deviation of σ = 0.357 × 10−3 cm−1. As for the ν1 + ν3 (E) combination band, about 3690 lines were assigned up to Kmax/Jmax = 45/55. Its v1 = v3 = 1 upper state (1931.577 5 cm−1) was treated using the same model recently applied to the v3 = 1 (E, 907.5413 cm−1) state. It yielded 21 free parameters through 3282 NZW experimental data, adjusted with σ = 0.344 × 10−3 cm−1 in the D-reduction. For the two excited states, the small and unobserved ℓ(0, 6) interaction was tested as useless. To confirm the adequacy of the vibrationally isolated models used, some other reductions of the Hamiltonian were tried. For the v3 = 2 state, the D-, L-, and LD-reductions led to similar σ’s, while the Q one was not successful. For the v1 = v3 = 1 state, the D- and Q-reductions gave comparable σ’s, while the QD-reduction was not as good. The corresponding unitary equivalence relations are generally more nicely fulfilled for the v3 = 2 state than for the v1 = v3 = 1 state. The three derivable anharmonicity constants in cm−1 are x33 = −4.1528, g33 = +1.8235 and x13 = −7.9652. 相似文献
4.
利用飞秒时间分辨光谱,可观测叠加在电子态动力学上的相干振动动力学. 从金团簇的相干振动中,不仅能提取电子与振动的耦合信息,也能得到力学性质和电子结构,进而有望实现微小质量探测等应用. 本文利用飞秒时间分辨的瞬态吸收探测了[Au25(SR)18]-团簇的相干振动动力学,通过对相干振动的频率、相位、波长分布的详细分析进一步揭示了其来源. 在[Au25(SR)18]-团簇的飞秒瞬态吸收动力学中可以观测到频率为40 cm-1和80 cm-1的两种振动,均来源于团簇中心Au13核的振动. 通过对相干振动的相位分析发现频率为80 cm-1的振动来自于对电子态之间吸收频率的调制,而频率为40 cm-1的振动来源于对电子态之间吸收强度的调制. 同时,研究发现[Au25(SR)18]-团簇相干振动的频率对其表面配体不敏感,该振动是来源于Au13核的本征性质. 相似文献
5.
X. J. Kuang X. Q. Wang G. B. Liu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,63(1):111-122
An all-electron scalar relativistic calculation on
Au
n
Pt (n = 1−12) clusters has been
performed by using density functional theory with the generalized gradient approximation
at PW91 level. Our results reveal that all the lowest energy geometries of
Au
n
Pt (n = 1−12) clusters may be
generated by substituting Pt atom for one gold atom of the
Au
n+1 cluster at the highest coordinated site. Compared with
corresponding pure Au
n+1 cluster, the lowest energy geometries
of Au
n
Pt clusters are distorted slightly and still keep the
planar structures due to the strong scalar relativistic effect in small gold cluster. The
Au-Pt bonds are stronger and most Au-Au bonds far from Pt atom are weaker than the
corresponding Au-Au bonds in pure Au
n+1 cluster. By
substituting Pt atom for one gold atom of Au
n+1 cluster at the
highest coordinated site, the relatively stable and inactive odd-numbered
Au
n+1 cluster becomes the relatively unstable and reactive
odd-numbered Au
n
Pt cluster, and the relatively unstable and
reactive even-numbered Au
n+1 cluster becomes the relatively
stable and inactive even-numbered Au
n
Pt cluster chemically
and electronically. All the Au
n
Pt clusters prefer low spin
multiplicity. The even-numbered Au
n
Pt clusters are found to
exhibit zero magnetic moment and the odd-numbered
Au
n
Pt clusters are found to possess magnetic moment with the
value of 1 μ
B. The odd-even alterations of magnetic moments
and electronic configurations for Au
n
Pt clusters are very
obvious and may be simply understood in terms of the electron pairing effect. 相似文献
6.
R. Boča 《Czechoslovak Journal of Physics》1990,40(6):629-645
Quasirelativstic and relativistic (four-component) versions of the CNDO (Complete Neglect of Differential Overlap) methods have been used in studying the electronic structure of octahedral2[CuF6]4–,2[AuF6]4– complexes and
m
[Cu6]
q
,
m
[Au6]
q
and
m
[Au6(PH3)6]
q
clusters for various charges,q, and spin multiplicities,m. A strong spin-orbit splitting of levels t1u in [Au6]2+ cluster removes the degeneracy of the ground electronic state3T1g into a nondegenerate state so that the Jahn-Teller instability disappears as a consequence of the relativistic effect. The phosphine ligands change the redox stability of the cluster as the orbital energies are shifted to higher values. On the contrary, the spin-orbit splitting of completely filled t2u levels in [AuF6]4– is irrelevant since the degeneracy of the ground electronic state2Eg (8g in the double group notation) remains unchanged. Consequently the Jahn-Teller instability of the octahedral geometry exists and thus a considerable tetragonal distortion appears.Part V: J. Quantum Chem.36 (1989) 727. 相似文献
7.
The structural and electronic properties of MAu−19 and M2Au−18 (M = Cu and Na) have been studied by the relativistic density-functional calculations. It is found that the most stable configurations of CuAu−19 and Cu2Au−18 are the face-centered and two-face-centered doped structures based upon the tetrahedral structure Au−20. In contrast, the ground states of Na-doped gold clusters (NaAu−19 and Na2Au−18) exhibit flat-cage configurations. The PES of these ground states are depicted that may be helpful to identify their configurations in the future experiments. The face-centered and two-face-centered doped tetrahedral structures of CuAu−19 and Cu2Au−18 have a large HOMO–LUMO gap, indicating that they are chemically stable. 相似文献
8.
M.A.A. Moussa M. Muralidhar M. Izumi M. Murakami 《Physica C: Superconductivity and its Applications》2009,469(15-20):1211-1214
Effects of a combined substitute of Yb and Nd on Y site on the superconducting properties of YBa2Cu3Oy have been studied. We synthesized Y1−x(Yb0.9Nd0.1)xBa2Cu3Oz compound with x = 0.2, 0.4, 0.6, 0.8 and 1.0. Here, the ratio of Yb–Nd was fixed to be 9:1 for obtaining 123 phase without secondary phases. The melt processing thermal profiles for Y1−x(Yb0.9Nd0.1)xBa2Cu3Oz with x = 0.2 and 0.4 and the addition of 40 mol% {Y1−x(Yb0.9Nd0.1)x}2BaCuO5 and 0.5 wt% Pt in air were determined on the basis of the thermal analysis results. All samples showed a low grain growth rate, particularly for high x values, which may be partially ascribed to un-optimized thermal schedules. Although almost all the samples exhibited low Jc values, the sample with x = 0.2 exhibited Tc of 88.8 K and a relatively high Jc value of 16,000 A/cm2 at 77 K for H//c-axis. 相似文献
9.
E.T. Seppälä M.J. Alava 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(3):407-424
We study the effect of an external field on (1 + 1) and (2 + 1) dimensional elastic manifolds, at zero temperature and with
random bond disorder. Due to the glassy energy landscape the configuration of a manifold changes often in abrupt, “first order”-type
of large jumps when the field is applied. First the scaling behavior of the energy gap between the global energy minimum and
the next lowest minimum of the manifold is considered, by employing exact ground state calculations and an extreme statistics
argument. The scaling has a logarithmic prefactor originating from the number of the minima in the landscape, and reads ΔE
1∼L
θ[ln(L
z
L
- ζ)]-1/2, where ζ is the roughness exponent and θ is the energy fluctuation exponent of the manifold, L is the linear size of the manifold, and Lz is the system height. The gap scaling is extended to the case of a finite external field and yields for the susceptibility
of the manifolds ∼L
2D + 1 - θ[(1 - ζ)ln(L)]1/2. We also present a mean field argument for the finite size scaling of the first jump field, h
1∼L
d - θ. The implications to wetting in random systems, to finite-temperature behavior and the relation to Kardar-Parisi-Zhang non-equilibrium
surface growth are discussed.
Received December 2000 and Received in final form April 2001 相似文献
10.
The anisotropic and isotropic components of the ν2, ν5 rotation-vibrational Raman bands of 13CH3F were obtained separately. The two upper states are coupled by a strong second-order Coriolis resonance. The anisotropic spectrum was analyzed by means of a program system due to R. Escribano. A contour simulation and a least-squares fit of 233 assigned transitions yielded values for ν5, ΔA5, ΔA2, and Aζ5a, 5b(z). The 13C shifts of ν2 and ν5 were obtained from the isotropic spectrum. 相似文献
11.
Ljiljana Puskar Evan G. Robertson Don McNaughton 《Journal of Molecular Spectroscopy》2006,240(2):244-250
We report a rovibrational analysis of the ν4 and ν6 fundamentals and the 2ν5 overtone of HNSO from high-resolution Fourier transform infrared spectra. The ν6 band (out-of-plane bend) centred at 757.5 cm−1 is c-type. The ν4 band (HNS bend) centred at 905.9 cm−1 is predominantly a-type with a very weak b-type component (). Numerous global perturbations and localized avoided crossings affecting the v4 = 1 rotational levels were successfully treated by inclusion of Fermi and c-axis Coriolis resonance terms between v4 = 1 and v5 = 2, and a b-axis Coriolis resonance term between v4 = 1 and v6 = 1. The latter term gives rise to an avoided crossing with an extraordinary ΔKa = 5 selection rule. The Fermi resonance between v4 = 1 and v5 = 2 gives rise to strong mixing of their rotational wavefunctions in the vicinity of Ka = 18. The resultant borrowing of intensity made it possible for 2ν5 transitions in the range Ka = 16–19 to be assigned and included in a global rovibrational treatment of all three band systems. 相似文献
12.
B. Sitamtze Youmbi Serge Zékeng Samuel Domngang Florent Calvayrac Alain Bulou 《Ionics》2012,18(4):371-377
To date, the fastest lithium ion-conducting solid electrolytes known are the perovskite-type ABO3 oxide, with A = Li, La and B = Ti, lithium lanthanum titanate (LLTO)
Li3x La( 2 \mathord