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1.
Yaojin Wang Davresh Hasanyan Menghui Li Junqi Gao Ravindranath Viswan Jiefang Li D. Viehland 《固体物理学:研究快报》2012,6(6):265-267
The tunability of magnetoelectric (ME) properties by applied dc electric field (E) was systematically investigated for a laminate composite consisting of Metglas, Pb(Zrx Ti1–x)O3 fiber, and interdigitated electrodes. The ME coefficients and equivalent magnetic noise were found to be dependent on E. This dependence is attributed to variations in the magnetic properties. The dielectric properties and noise charge density were relatively invariant to E. A 1.3× improvement in the ME coefficient was obtained at the Villari point under E = 300 V/mm relative to E = 0 V/mm. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
2.
On the Plasma Chemistry of an RF Discharge Containing Aluminium Tri‐Isopropoxide Studied by FTIR Spectroscopy
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In Ar and Ar/N2 radio frequency (RF) discharges with admixtures of aluminium tri‐isopropoxide (ATI) the fragmentation of this metal‐organic precursor was studied by means of Fourier Transform Infrared (FTIR) spectroscopy using an optical long path cell providing an optical length of l = 17.2 m. The experiments were performed in an asymmetric capacitively coupled process plasma at a frequency of f = 13.56 MHz and at pres‐sure values in the range of p = 1–10.5 Pa. The discharge power was chosen between P = 10–100 W. Using FTIR spectroscopy the evolution of the concentrations of ATI and of six stable molecules, CH4, C2H2, C2H4, C2H6, CO and HCN, was monitored under flowing conditions at gas flows of Φtotal = 0.5–14.5 sccm in the discharge. The concentrations of the reaction products were measured tobe between 2 x 1012 molecules cm–3 as e.g. found for C2H4and C2H6, and 5 x 1013 molecules cm–3, as e.g. in the case of CO. In the plasma a complete dissociation of the precursor ATI was found at a power value of about P = 80 W independent on the admixture of Ar or N2. The fragmentation efficiency (FE) of the reaction products which originate from the ATI molecules ranges between 0.2 and 4 x 1016 molecules J–1 while the fragmentation rate (FR) reached up to 2.5 x 1018 molecules s–1. The multi component detection ability of the spectrometer served to analyse the carbon balance of the by‐product formation. For all experiments, the carbon balance never exceeded 25%. Therefore, in the plasmas the majority of the provided carbon is most likely deposited at the reactor walls or forms dust particles or higher molecular CxHy. The conversion efficiencies (CE) of the produced molecular species ranges between 0.1 x 1015 molecules J–1 for C2H4 and 5 x 1015 molecules J–1 for C2H6 depending on the discharge conditions of the RF plasma. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
3.
Wang Jun Liu Xiang-Lin Yang An-Li Zheng Gao-Lin Yang Shao-Yan Wei Hong-Yuan Zhu Qin-Sheng Wang Zhan-Guo 《Applied Physics A: Materials Science & Processing》2011,104(4):1099-1103
Four novel dmit complexes: [(C2H5)4N][Ni (dmit)2], [(C3H7)4N][Ni(dmit)2], [(C2H5)4N][Au(dmit)2] and [(C3H7)4N][Au(dmit)2], abbreviated as EtNi, PrNi, EtAu, and PrAu, were synthesized. The third-order nonlinear optical properties of them in acetonitrile
solutions were investigated by using the Z-scan technique with 20 ps pulses width at 1064 nm. When the on-axis irradiance
at focus I
0 was 5.025 GW/cm2, the nonlinear refraction coefficient n
2, the third-order nonlinear susceptibility χ
(3), the molecular second-order hyperpolarizability γ of the four types of material were obtained with subject to Z-scan curves, and these indexes were with the magnitudes of
10−18 m2/W, 10−13 esu, and 10−31 esu, respectively. The nonlinear absorption coefficient β of Ni samples had the 10−12 m/W scale. The impact of different metals and cations on the third-order nonlinear optical properties of materials was analyzed.
Through the derivation, the result suggests that these dmit complexes are promising candidates for applications to nonlinear
optical devices manufacture in the near-infrared waveband. 相似文献
4.
Qing Zeng Zucheng Li Yujie Zhang Zhirong Sun Yingzi Wang Fubin Jiang 《Journal of Physical Organic Chemistry》2012,25(12):1275-1285
The nature and strength of metal–ligand bonds in organotransition‐metal complexes are crucial to the understanding of organometallic reactions and catalysis. Quantum chemical calculations at different levels of theory have been used to investigate heterolytic Fe–N bond energies of para‐substituted anilinyldicarbonyl(η5‐cyclopentadienyl)iron [p‐G‐C6H4NH(η5‐C5H5)Fe(CO)2, abbreviated as p‐G‐C6H4NHFp (1), where G = NO2, CN, COMe, CO2Me, CF3, Br, Cl, F, H, Me, MeO, and NMe2] and para‐substituted α‐acetylanilinyldicarbonyl(η5‐cyclopentadienyl)iron [p‐G‐C6H4N(COMe)(η5‐C5H5)Fe(CO)2, abbreviated as p‐G‐C6H4N(COMe)Fp (2)] complexes. The results show that BP86 and TPSSTPSS can provide the best price/performance ratio and more accurate predictions in the study of ΔHhet(Fe–N)'s. The linear correlations [r = 0.98 (g, 1a), 0.93 (g, 2b)] between the substituent effects of heterolytic Fe–N bond energies [ΔΔHhet(Fe–N)'s] of series 1 and 2 and the differences of acidic dissociation constants (ΔpKa) of N–H bonds of p‐G‐C6H4NH2 and p‐G‐C6H4NH(COMe) imply that the governing structural factors for these bond scissions are similar. And the linear correlations [r = ?0.99 (g, 1c), ?0.92 (g, 2d)] between ΔΔHhet(Fe–N)'s and the substituent σp? constants show that these correlations are in accordance with Hammett linear free energy relationships. The polar effects of these substituents and the basis set effects influence the accuracy of ΔHhet(Fe–N)'s. ΔΔHhet(Fe–N)'s(1, 2) follow the captodative principle. MEα‐COMe, para‐Gs include the influences of the whole molecules. The correlation of MEα‐COMe, para‐Gs with σp? is excellent. MEα‐COMe, para‐Gs rather than ΔΔHhet(Fe–N)'s in series 2 are more suitable indexes for the overall substituent effects on ΔHhet(Fe–N)'s(2). Insight from this work may help the design of more effective catalytic processes. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
5.
R. Helburn M. Bartoli K. Pohaku J. Maxka D. Compton B. Creedon C. Stimpson 《Journal of Physical Organic Chemistry》2007,20(5):321-331
Hydrophobic forms of the N,N‐dialkyl‐4‐nitroaniline (DNAP) (p‐O2NC6H4NR2) ( 1a–f ) and alkyl‐4‐nitrophenyl ether (p‐O2NC6H4OR) ( 2a–c ) solvatochromic π* indicators have been characterized and compared with respect to: (a) solvatochromic bandshape, (b) sensitivity expressed as ?s , ( / d π * ), and (c) trends in ? s with increasing length of alkyl chain(s) on the probe molecule. ? Octyl 4‐nitrophenyl ether (p‐O2NC6H4OC8H17) ( 2b ) and ? decyl 4‐nitrophenyl ether (p‐O2N C6H4 OC10H21) ( 2c ) were synthesized and their solvatochromic UV/Vis absorption bands were found to maintain a Gausso‐Lorentzian bandshape for the indicators in non‐polar and alkyl substituted aromatic solvents, for example, hexane(s) and mesitylene. Corresponding absorption bands for 1a–f display increasing deviation from a Gausso‐Lorentzian shape in the same solvents as the alkyl chains on the indicator are increased in length all the way to C10 and C12, for example, N,N‐didecyl‐4‐nitroaniline (p‐O2NC6H4N (C10H21)2) and N,N‐didodecyl‐4‐nitroaniline (p‐O2NC6H4N (C12H25)2) ( 1d–f ). A plot of ? s versus Cn follows a 1st order decay for the DNAP indicators but is linear for the alkyl 4‐nitrophenyl ethers. A discussion of how the long alkyl chains on the two types of indicators affect the orientation and overlap of n and π * orbitals, and resulting solvatochromic bands is presented. For DNAP, overextending the alkyl chains to obtain greater hydrophobic character may cause the alkane component to dominate solute‐solvation processes at the expense of the probe's fundamental solvatochromic character. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
6.
Qing Zeng Zucheng Li Daxiong Han Ling Dong Huaqiang Zhai Bin Liu Genben Bai Yujie Zhang 《Journal of Physical Organic Chemistry》2014,27(2):142-155
The knowledge of accurate bond strengths is a fundamental basis for a proper analysis of chemical reaction mechanisms. Quantum chemical calculations at different levels of theory have been used to investigate heterolytic Fe–O and Fe–S bond energies of para‐substituted phenoxydicarbonyl(η5‐cyclopentadienyl) iron [p‐G‐C6H4O(η5‐C5H5)Fe(CO)2, abbreviated as p‐G‐C6H4OFp ( 1 ), where G = NO2, CN, COMe, CO2Me, CF3, Br, Cl, F, H, Me, MeO, and NMe2] and para‐substituted benzenethiolatodicarbonyl(η5‐cyclopentadienyl) iron [p‐G‐C6H4S(η5‐C5H5)Fe(CO)2, abbreviated as p‐G‐C6H4SFp ( 2 )] complexes. The results show that BP86 and TPSSTPSS can provide the best price/performance ratio and more accurate predictions in the study of ΔHhet(Fe–O)'s and ΔHhet(Fe–S)'s. The excellent linear free‐energy relations [r = 0.99 (g, 1a), 1.00 (g, 2b)] among the ΔΔHhet (Fe–O)'s and Δpka's of O–H bonds of p‐G‐C6H4OH or ΔΔHhet(Fe‐S)'s and Δpka's of S–H bonds of p‐G‐C6H4SH imply that the governing structural factors for these bond scissions are similar. And the linear correlations [r = ?0.99 (g, 1g), ?0.98 (g, 2h)] among the ΔΔHhet (Fe‐O)'s or ΔΔHhet(Fe‐S)'s and the substituent σp? constants show that these correlations are in accordance with Hammett linear free‐energy relationships. The polar effects of these substituents and the basis set effects influence the accuracy of ΔHhet(Fe–O)'s or ΔHhet(Fe–S)'s. ΔΔHhet(Fe–O)'s(g) ( 1 ) and ΔΔHhet(Fe–S)'s(g)( 2 ) follow the Capto‐dative principle. The substituent effects on the Fe–O bonds are much stronger than those on the less polar Fe–S bonds. Insight from this work may help the design of more effective catalytic processes. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
7.
Current–voltage, radio‐frequency (RF) and noise characteristics of single‐wall multi‐tube carbon nanotube (CNT) transistors were measured at cryogenic temperatures. Compared to an ambient temperature (Ta) of 300 K, only a slight drain current increase at Ta = 77 K was observed. In addition, a weak dependence of the maximum value of the current gain cut‐off frequency (fT) on Ta was obtained, indicating that fT is rather limited by the device intrinsic quantum and extrinsic capacitances than by an improved mobility due to reduced optical phonon scattering at low Ta. A noise analysis of the devices at Ta = 10 K reveals that the noise factor (NF) improvement at very low temperatures is related to the reduced Nyquist noise of all resistive transistor noise contributors. Since the main noise source in CNTFETs is the shot noise, NF remains comparatively high even at Ta = 10 K.
8.
Yaojin Wang David Gray David Berry Junqi Gao Jiefang Li D. Viehland Haosu Luo 《固体物理学:研究快报》2011,5(7):232-234
We have experimentally and theoretically investigated the equivalent magnetic noise in a magnetoelectric Metglas/ 0.7Pb(Mg1/3Nb2/3)O3‐0.3PbTiO3 laminate sensor unit by considering the constituent noise sources of dielectric loss (NDE) and DC leakage resistance (NR). In the low frequency range (f = 1 Hz), theory predicts that NR dominates the noise charge (1.6 times larger than NDE), with a 1 Hz noise of 9.1\;{\rm pt}/\sqrt {\rm Hz}. The experimental equivalent magnetic noise was 10.8\;{\rm pt}/\sqrt {\rm Hz}. This observed value is slightly higher than the predicted one, which might be due to an oversimplification of the theoretical model in terms of electrical charge amplifier and external vibration noise sources. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
9.
10.
采用化学镀和黏接法制备层状磁电复合材料Ni/PZT/TbFe2,研究其磁电性能及谐振频率随Ni层厚度的变化情况. 结果表明:Ni/PZT/TbFe2层状磁电复合材料与其他结构的磁电性能不同,其一阶弯曲谐振峰值和纵向谐振峰值都很大. 随着Ni层厚度的增加,Ni/PZT/TbFe2层状磁电复合材料的一阶纵向谐振峰值逐渐增大. 结合实验数据和理论计算值得出了材料的一阶弯曲谐振频率fr1和一阶纵向谐振频率f
关键词:
磁电效应
正磁致伸缩
负磁致伸缩
谐振频率 相似文献
11.
Computation of non-linearity parameter (B/A), molecular radius (r
m) and intermolecular free length (L
f) for H2O, C6H6, C6H12, CH3OH, C2H5OH and their deuterium-substituted compounds have been carried out at four different temperatures, viz., 293.15, 303.15, 313.15
and 323.15 K. The aim of the investigation is an attempt to study the isotopic effects on the non-linearity parameter and
the physicochemical properties of the liquids, which in turn has been used to study their effect on the intermolecular interactions
produced thereof. 相似文献
12.
Giant positive or negative magnetoresistance is calculated in a band model. The spectra of the band electrons in a two-sublattice
antiferromagnetic intermetallic compound depend on the antiferromagnetism vector L(T,H). The metamagnetic transition to the ferromagnetic phase is accompanied by splitting with respect to the spin σ, displacement of the energy bands, and a decrease in the effective masses of the band electrons. This mechanism of giant
negative magnetoresistance is also accompanied by an increase in the relaxation time τjσ. Scattering by chemical-bond fluctuations is considered as the main relaxation mechanism. Giant positive magnetoresistance
results from a four-subband model of 4f and 5f intermetallic compounds. The electron effective masses m
jσ(J
jT
) of the (j,σ) bands increase with the mean angular momentum J
1T
(T,H) of an ion in the jth sublattice of 4(5)f ions. The thermodynamics of such a four-sublattice model, the nonlinear magnetization and magnetoresistance curves, and the
nonmonotonic dependence of the specific heat C
m(T,H) on the field H are calculated.
Fiz. Tverd. Tela (St. Petersburg) 39, 1806–1814 (October 1997) 相似文献
13.
Knowledge of the strength of the metal–ligand bond breaking and formation is fundamental for an understanding of the thermodynamics underlying many important stoichiometric and catalytic organometallic reactions. Quantum chemical calculations at different levels of theory have been used to investigate heterolytic Fe―C bond energies of para‐substituted benzyldicarbonyl(η5‐cyclopentadienyl)iron, p‐G‐C6H4CH2Fp [1, G = NO2, CN, COMe, CO2Me, CF3, Br, Cl, F, H, Me, MeO, NMe2; Fp = (η5‐C5H5)(CO)2Fe], and para‐substituted α‐cyanobenzyldicarbonyl(η5‐cyclopentadienyl)iron, p‐G‐PANFp [2, PAN = C6H4CH(CN)]. The results show that BP86 and TPSSTPSS can provide the best price/performance ratio and more accurate predictions in the study of ΔHhet(Fe―C)'s. The good linear correlations [r = 0.98 (g, 1a), 0.99 (g, 2b)] between the substituent effects of heterolytic Fe―C bond energies [ΔΔHhet(Fe―C)'s] of series 1 and 2 and the differences of acidic dissociation constants (ΔpKa) of C―H bonds of p‐G‐C6H4CH3 and p‐G‐C6H4CH2CN imply that the governing structural factors for these bond scissions are similar. And the excellent linear correlations [r = ?1.00 (g, 1c), ?0.99 (g, 2d)] between ΔΔHhet(Fe―C)'s and the substituent σp? constants show that these correlations are in accordance with Hammett linear free energy relationships. The polar effects of these substituents and the basis set effects influence the accuracy of ΔHhet(Fe―C)'s. ΔΔHhet(Fe―C)'s(1, 2) follow the Capto‐dative Principle. The detailed knowledge of the factors that determine the Fp―C bond strengths would greatly aid in understanding reactivity patterns in many processes. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
14.
Birendra Kumar Deepti Tikariha Kallol K. Ghosh Nadia Barbero Pierluigi Quagliotto 《Journal of Physical Organic Chemistry》2013,26(8):626-631
Kinetic study has been performed to understand the reactivity of novel cationic gemini surfactants viz. alkanediyl‐α,ω‐bis(hydroxyethylmethylhexadecylammonium bromide) C16‐s‐C16 MEA, 2Br? (where s = 4, 6) in the cleavage of p‐nitrophenyl benzoate (PNPB). Novel cationic gemini C16‐s‐C16 MEA, 2Br? surfactants are efficient in promoting PNPB cleavage in presence of butane 2,3‐dione monoximate and N‐phenylbenzohydroxamate ions. Model calculation revealed that the higher catalytic effect of ethanol moiety of gemini surfactants (C16H33N+ C2H4OH CH3 (CH2)S N+ C2H4OH CH3C16H33, 2Br?, s = 4, 6) is due to their higher binding capacity toward substrate. This is in line with finding that binding constants for novel series of cationic gemini surfactants are higher than conventional cationic gemini (C16H33N+(CH3)2(CH2)SN+(CH3)2C16H33, 2Br?, s = 10, 12), cetyldimethylethanolammonium bromide and zwitterionic surfactants, i.e. CnH2n+1N+Me2 (CH2)3 SO3? (n = 10; SB3‐10). The fitting of kinetic data was analyzed by the pseudophase model. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
15.
The edge of the wedge theorem is generalized to the case where one only assumes the existence and equality of the distribution boundary values off
±(z) and all their derivatives on some analytic curveC inR
n
. Heref
±(z) are holomorphic inR
n
±iC, respectively, whereC is a convex cone, andC has its tangent vector inC at every point. Under these assumptions there exists an analytic continuationf(z) holomorphic in some complex neighbourhood of the double cone generated byC. A proof is also given of the connection between the existence of a distribution boundary value and the growth of the holomorphic function near the boundary. 相似文献
16.
Sergey I. Vdovenko Igor I. Gerus Valery P. Kukhar 《Journal of Physical Organic Chemistry》2007,20(3):190-200
The kinetics of the reaction of β‐substituted β‐alkoxyvinyl trifluoromethyl ketones R1O‐CR2?CH‐COCF3 ( 1a – e ) [( 1a ), R1?C2H5, R2?H; ( 1b ), R1?R2?CH3; ( 1c ), R1?C2H5, R2?C6H5; ( 1d ), R1?C2H5, R2?V?pNO2C6H4; ( 1e ), R1?C2H5, R2?C(CH3)3] with four aliphatic amines ( 2a – d ) [( 2a ), (C2H5)2NH; ( 2b ), (i‐C3H7)2NH; ( 2c ), (CH2)5NH; ( 2d ), O(CH2CH2)2NH] was studied in two aprotic solvents, hexane and acetonitrile. The least reactive stereoisomeric form of ( 1a – d ) was the most populated ( E‐s‐Z‐o‐Z ) form, whereas in ( 1e ), the more reactive form ( Z‐s‐Z‐o‐Z ) dominated. The reactions studied proceeded via common transition state formation whose decomposition occurred by ‘uncatalyzed’ and/or ‘catalyzed’ route. Shielding of the reaction centre by bulky β‐substituents lowered abruptly both k′ (‘uncatalyzed’ rate constant) and k″ (‘catalyzed’ rate constant) of this reaction. Bulky amines reduced k″ to a greater extent than k′ as a result of an additional steric retardation to the approach of the bulky amine to its ammonium ion in the transition state. An increase in the electron‐withdrawing ability of the β‐substituent increased ‘uncatalyzed’ k′ due to the acceleration of the initial nucleophile attack (k1) and ‘uncatalyzed’ decomposition of transition state (k2) via promoting electrophilic assistance (through transition state 8 ). The amine basicity determined the route of the reaction: the higher amine basicity, the higher k3/k2 ratio (a measure of the ‘catalyzed’ route contribution as compared to the ‘uncatalyzed’ process) was. ‘Uncatalyzed’ route predominated for all reactions; however in polar acetonitrile the contribution of the ‘catalyzed’ route was significant for amines with high pKa and small bulk. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
17.
The optical nonlinearities of Cu(mpo)2 [formula = C10H8N2CuO2S2] complex have firstly been investigated by using the Z-scan technique with a nanosecond-pulsed Nd:YAG laser at its second harmonic (532 nm) radiation. The nonlinear optical absorption and refraction coefficients of Cu(mpo)2 have been measured with the different on-axial peak irradiances I
0 at the waist ranging from 0.48 to 5.66 GW/cm2. The nonlinear transmittance characteristics exhibit the near resonant two-photon absorption (TPA) at 532 nm and are explained by a population redistribution model. The nonlinear absorption originates from the near resonant TPA while the mechanism of the nonlinear refraction is the near resonant TPA transition enhancement. The linear increasing dependences of the optical nonlinearities on the incident irradiance arise from the population redistribution due to the near resonant TPA. 相似文献
18.
We study memoryless, discrete time, matrix channels with additive white Gaussian noise and input power constraints of the
form Y
i = ∑
j
H
ij
X
j
+ Z
i
, where Y
i
, X
j
and Z
i
are complex, i = 1… m, j = 1… n, and H is a complex m× n matrix with some degree of randomness in its entries. The additive Gaussian noise vector is assumed to have uncorrelated
entries. Let H be a full matrix (non-sparse) with pairwise correlations between matrix entries of the form E[H
ik
H
*
jl] = 1/n
C
ij
D
kl, where C, D are positive definite Hermitian matrices. Simplicities arise in the limit of large matrix sizes (the so called large-n limit) which allow us to obtain several exact expressions relating to the channel capacity. We study the probability distribution
of the quantity f(H) = log (1+PH
†
SH) . S is non-negative definite and hermitian, with TrS = n and P being the signal power per input channel. Note that the expectation E[f(H)], maximised over S, gives the capacity of the above channel with an input power constraint in the case H is known at the receiver but not at the transmitter. For arbitrary C, D exact expressions are obtained for the expectation and variance of f(H) in the large matrix size limit. For C = D = I, where I is the identity matrix, expressions are in addition obtained for the full moment generating function for arbitrary (finite)
matrix size in the large signal to noise limit. Finally, we obtain the channel capacity where the channel matrix is partly
known and partly unknown and of the form α; I+ β H, α,β being known constants and entries of H i.i.d. Gaussian with variance 1/n. Channels of the form described above are of interest for wireless transmission with multiple antennae and receivers. 相似文献
19.
Denisa Tarabová Viktor Milata Jiří Hanusek 《Journal of Physical Organic Chemistry》2013,26(6):503-509
The kinetics and mechanism of the nucleophilic vinylic substitution of dialkyl (alkoxymethylidene)malonates (alkyl: methyl, ethyl) and (ethoxymethylidene)malononitrile with substituted hydrazines and anilines R1–NH2 (R1: (CH3)2N, CH3NH, NH2, C6H5NH, CH3CONH, 4‐CH3C6H4SO2NH, 3‐ and 4‐X‐C6H4; X: H, 4‐Br, 4‐CH3, 4‐CH3O, 3‐Cl) were studied at 25 °C in methanol. It was found that the reactions with all hydrazines (the only exception was the reaction of (ethoxymethylidene)malononitrile with N,N‐dimethylhydrazine) showed overall second‐order kinetics and kobs were linearly dependent on the hydrazine concentration which is consistent with the rate‐limiting attack of the hydrazine on the double bond of the substrate. Corresponding Brønsted plots are linear (without deviating N‐methyl and N,N‐dimethylhydrazine), and their slopes (βNuc) gradually increase from 0.59 to 0.71 which reflects gradually increasing order of the C–N bond formed in the transition state. The deviation of both methylated hydrazines is probably caused by the different site of nucleophilicity/basicity in these compounds (tertiary/secondary vs. primary nitrogen). A somewhat different situation was observed with the anilines (and once with N,N‐dimethylhydrazine) where parabolic dependences of the kinetics gradually changing to linear dependences as the concentration of nucleophile/base increases. The second‐order term in the nucleophile indicates the presence of a steady‐state intermediate ‐ most probably T±. Brønsted and Hammett plots gave βNuc = 1.08 and ρ = ?3.7 which is consistent with a late transition state whose structure resembles T±. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
20.
Density functional theory study of substituent effects on gas‐phase heterolytic Fe–O and Fe–S bond energies of m‐G‐C6H4OFe(CO)2(η5‐C5H5) and m‐G‐C6H4SFe(CO)2(η5‐C5H5)
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Qing Zeng Zucheng Li Yi‐Bo Wang Huaqiang Zhai Bin Liu Ou Tao Ling Dong Jun Guan Yujie Zhang 《Journal of Physical Organic Chemistry》2017,30(1)
The knowledge of accurate bond strengths is a fundamental basis for a proper analysis of chemical reaction mechanisms. Quantum chemical calculations at different levels of theory have been used to investigate heterolytic Fe–O and Fe–S bond energies of (meta‐substituted phenoxy)dicarbonyl(η5‐cyclopentadienyl) iron [m‐G‐C6H4OFp ( 1 )] and (meta‐substituted benzenethiolato)dicarbonyl(η5‐cyclopentadienyl) iron [m‐G‐C6H4SFp ( 2 )] complexes. In this study, Fp is (η5‐C5H5)Fe(CO)2, and G is NO2, CN, COMe, CO2Me, CF3, Br, Cl, F, H, Me, MeO, and NMe2. The results show that Tao–Perdew–Staroverov–Scuseria and Becke's power‐series ansatz from 1997 with dispersion corrections functionals can provide the best price/performance ratio and accurate predictions of ΔHhet(Fe–O)'s and ΔHhet(Fe–S)'s. The excellent linear free energy relations [r = 1.00 (g, 1e), 1.00 (g, 2b)] among the ΔΔHhet (Fe–O)'s and δΔG0 of O?H bonds of m‐G‐C6H4OH or ΔΔHhet(Fe–S)'s and ΔpKa's of S?H bonds of m‐G‐C6H4SH imply that the governing structural factors for these bond scissions are similar. And, the linear correlations [r = ?0.97 (g, 1 g), ?0.97 (g, 2 h)] among the ΔΔHhet (Fe–O)'s or ΔΔHhet(Fe–S)'s and the substituent σm constants show that these correlations are in accordance with Hammett linear free energy relationships. The inductive effects of these substituents and the basis set effects influence the accuracy of ΔHhet(Fe–O)'s or ΔHhet(Fe–S)'s. The ΔΔHhet(Fe–O)'s(g) (1) and ΔΔHhet(Fe–S)'s(g)(2) follow the capto‐dative Principle. The substituent effects on the Fe–O bonds are much stronger than those on the less polar Fe–S bonds. Insight from this work may help the design of more effective catalytic processes. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献