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1.
The frontier orbital interactions of electron pushing and drawing substituents with ferrocenyl group were analyzed based on the electrochemical,UV visible spectral and spectroelectrochemical results of five ferrocene derivatives,R-Fc-A1(PⅠ),A1-Fc-A1(PⅡ),D-Fc-R (PⅢ),D-Kc-A1(PIV) and D-Fc-A2(PV)(R,CH2OH;A1 CHO;A2,CH=C(CN)2 and D,(C18H37)2N-C6H4-CH=CH) It was found that there are strong interactions of the LUMO (πA) of electron drawing substituents with le2g(dxy,dx2 y2)and e2u of the ferroeenyl group because the energy levels of πA and e2g,C2U of (Cp )2 are close,which lower not only the energy levels of bonded orbits,πA+ and dx2-y2+[πA] of PⅠ,PⅡ,PⅣ and PⅤobviously,but also those of their non-bonded orbu dxy For PⅢ,PⅣ and PⅤ,there are strong interactions of HOMO(πD) of the electron pushing substituent with le of the ferrocenyl group because the levels of πD and e of (Cp)2 are close,which result in the formation of anti-bonded orbit,πD- and bonded orbit 相似文献
2.
V. P. Novikov S. A. Tarasenko S. Samdal L. V. Vilkov 《Journal of Structural Chemistry》2000,41(2):217-230
The geometrical parameters for 1,1-dimethylsilacyclobiitane and 1,1,3,3-tetramethyl-13-disilacyclobutune are detemiined by
gas phase electron diffraction analysis using a dynamic model, which considers ring inversion as a large-amplitude motion.
The structural and potential function parameters were refined with allowance for molecular geometry relaxation estimated by
quantum chemical calculations with an HF/6-311G** basis. The potential function of 1,1-dim ethylsilacyclobutane is represented
as V(ϕ) = V0[(ϕ/ϕe)2 − 1]2 with V0 = 1.3 ± 1.2 kcallmole and ϕe = 29.7±4.5°, where ϕ is the ring puckering angle. A more reliable estimate for the height of the barrier (V0 = 0.56 kcallmole) was obtained by solving the one-dimensional quantum vibrational problem and by fitting the frequency of
the 0 →2 transition to the experimental value. For 1,1,3,3-tetram ethyl-1,3-disilacyclobutane, the potential function is adequately
represented bx V(ϕ) = Aϕ2, where A = (4.9 ± 1.8) · 10−4 kcall(mole · deg2) with a minimum coiresponding to a planar ring conformation with ϕ = 0°. The calculated structural parameters are compared
with the data for related compounds.
Translated fromZhumal Struktumoi Khimii. Vol. 41, No. 2, pp. 269–284, March–April, 2000 相似文献
3.
A temperature-dependent integrated kinetics for the overall process of photosynthesis in green plants is discussed. The C4 plants are chosen and in these plants, the rate of photosynthesis does not depend on the partial pressure of O2. Using some basic concepts like chemical equilibrium or steady state approximation, a simplified scheme is developed for
both light and dark reactions. The light reaction rate per reaction center (R′
1) in thylakoid membrane is related to the rate of exciton transfer between chlorophyll neighbours and an expression is formulated
for the light reaction rate R′
1. A relation between R′
1 and the NADPH formation rate is established. The relation takes care of the survival probability of the membrane. The CO2 saturation probability in bundle sheath is also taken into consideration. The photochemical efficiency (ϕ) is expressed in terms of these probabilities. The rate of glucose production is given by R
glucose = (8/3)(R′
1
v
L
)ϕ(T)
g
(T) ([G3P]/[P
i]2
leaf)SS
Q
G3P→glucose where g is the activity quotient of the involved enzymes, and G3P represent glycealdehyde-3-phosphate in steady state. A Gaussian
distribution for temperature-dependence and a sigmoid function for de-activation are incorporated through the quotient g. In general, the probabilities are given by sigmoid curves. The corresponding parameters can be easily determined. The theoretically
determined temperature-dependence of photochemical efficiency and glucose production rate agree well with the experimental
ones, thereby validating the formalism. 相似文献
4.
Almuth Laeuter Hans-Robert Volpp Jai P. Mittal Rajesh K. Vatsa 《Journal of Chemical Sciences》2007,119(4):277-282
The collision-free, room temperature gas-phase photodissociation dynamics of CH3CFCl2 (HCFC-141b) was studied using Lyman-α laser radiation (121.6 nm) by the laser photolysis/laser-induced fluorescence ‘pump/probe’ technique. Lyman-α radiation was used both to photodissociate the parent molecule and to detect the nascent H atom products via (2p
2P → 1s
2S) laser-induced fluorescence. Absolute H atom quantum yield, ϕH = (0.39 ± 0.09) was determined by calibration method in which CH4 photolysis at 121.6 nm was used as a reference source of well-defined H atom concentrations. The line shapes of the measured
H atom Doppler profiles indicate a Gaussian velocity distribution suggesting the presence of indirect H atom formation pathways
in the Lyman-α photodissociation of CH3CFCl2. The average kinetic energy of H atoms calculated from Doppler profiles was found to be E
T(lab) = (50 ± 3) kJ/mol. The nearly statistical translational energy together with the observed Maxwell-Boltzmann velocity distribution
indicates that for CH3CFCl2 the H atom forming dissociation process comes closer to the statistical limit. 相似文献
5.
A series of polyads consisting of covalently-(CH2)4-linked fluorescein with carbazole and violger.Live been synthesized and characterized The studies of absorption,emission spectra and fluorescence lifetime quenching indicated that the intramolecular fluorescence quenching of fluorescein by violgen is mainly a static process through the formation of non emission complex (fluorescence quenching efficiency φQ=0.97,lifetime quenching efficiency φH 0,quenching efficiency of formation of non-emission complex φC=0.97); while the quenching by carbazole is mainly a dynamic electron transfer process (φQ=0.63,φET=0.63,φC=0).In the violgen-fluorescein-carbazole triads,φQ=0.97,Q ET=0.65,φC=0.32,which suggests that the photoinduced interaction of fluorescein-carbazole pair and that of violgen-fluorescein pair are in a competitive process,the dynamic electron transfer from carbazole to fluorecein is dominant in the process The free energy change of the photoinduced electron transfer and the back reac-tiorns i 相似文献
6.
V. G. Kokacheva L. V. Menshikova S. K. Talitskikh P. G. Khalatur 《Journal of Structural Chemistry》1995,36(5):734-738
A system of Ornstein-Zernike integral equations is solved numerically to determine the heats of vaporization ΔHV of liquid ethane, propane, and n-butane. It is shown that the calculations (the deformations of valence bonds and bond angles
in the liquid-phase molecules are ignored) give rather accurate values of ΔHV, which are in agreement with the corresponding experimental data. On the other hand, it is established that if there are
intramolecular rotational degrees of freedom, ΔHV depends on the angle of internal rotation ϕ. The function ΔHV(ϕ) is minimum for trans-conformations (ϕ=0) and maximum for cis-conformations (ϕ=180°). Hence, intermolecular interactions
stabilize compact (convolute) conformations. The energy of this effect is of the order of 1 kJ/mole.
Tver State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 5, pp. 808–813, September–October, 1995.
Translated by I. Izvekova 相似文献
7.
M. N. Roy R. K. Das A. Bhattacharjee 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(13):2201-2210
Apparent molar volumes ϕν and viscosity B-coefficients for tetrabutyl ammonium bromide (TBAB) in (0.00, 0.05, 0.10, and 0.15) mol dm−3 aqueous ascorbic acid solutions have been determined from solution density and viscosity measurements at temperatures over
the range 298.15 to 318.15 K as function of concentration of ascorbic acid solutions. In the investigated temperature range,
the relation: ϕν0 = a
0 + a
1
T + a
2
T
2, have been used to describe the partial molar volume ϕν0. These results, in conjunction with the results obtained in pure water, have been used to calculate the standard volumes
of transfer Δϕ
ν
0 and viscosity B-coefficients of transfer for TBAB from water to aqueous ascorbic acid solutions for rationalizing various interactions in
the ternary solutions. The structure making or breaking ability of TBAB has been discussed in terms of the sign of (δ2ϕν0/δT
2)
P
. An increase in the transfer volume of TBAB with increasing ascorbic acid concentration has been explained by Friedman-Krishnan
co-sphere model. The activation parameters of viscous flow for the ternary solutions studied have also been calculated and
explained by the application of transition state theory. 相似文献
8.
9.
O. E. Ayala D. Lardizábal A. Reyes M. I. Rosales J. A. Matutes A. González Arias 《Journal of Thermal Analysis and Calorimetry》2000,59(3):943-949
Expressions for calculating the cation vacancy contents of MnZn ferrites from thermogravimetric curves are presented together
with some experimental data. In a single-phase MnZn ferrite synthesized by conventional ceramic procedures, the O2 evolution accompanying ferrite formation follows the formal equation.
Mn2+
σα Znσβ Fe3+
2σ(1–γ) [V ]σ/4(1–2γ) O4 =σ'/σ Mn2+
σ(α–2ϕ) Znσβ Fe2+
2σθ Mn3+
2σϕ Fe3+
2σ(1–γ–θ) [V ]σ/4(1–2γ–3ϕ) O4 +σ'φ/2O2 (g)
where α and β denote the MnO and ZnO mole fractions in the primary mixture γ=α+β, θ and ϕ depend on the quantities of Fe2+ and Mn3+ formed, respectively, φ=θ–ϕ and σ'/σ is a function of the former parameters. Even though the relative amounts of Fe2+ /Fe3+ and Mn2+ /Mn3+ remain uncertain, the vacancy content [V ] of the ferrite can be determined because it depends on φ alone, which is related to the change in mass of the sample as
the synthesis takes place through the equation
φ=(1.5–γ) μβ /μO2 (1–m
f /m
i )
Here, m
i and m
f are the masses of the sample before and after O2 evolution, μB is the formula mass of the ferrite and μO2 is the O2 molar mass. Practically vacancy-free single-phase MnZn ferrite samples were obtained by sintering in air at 1250°C and cooling
in pure N2 .
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
采用高温固相法制备了Sr_3Y(BO_3)_3:xTm~(3+),yDy~(3+)荧光粉,并通过XRD、SEM和荧光光谱仪对样品的物相、微观形貌、发光性能、能量传递机制和CIE色坐标进行了分析。结果表明:Sr_3Y(BO_3)_3:xTm~(3+)荧光粉在监测波长为359 nm时发射蓝光,Tm~(3+)的浓度淬灭点为x=0.08;在Sr_3Y(BO_3)_3:0.08Tm~(3+),yDy~(3+)荧光粉中,随着Dy~(3+)掺杂浓度的增加,Tm~(3+)的发光强度降低而Dy~(3+)发光强度却先增加后降低,Dy~(3+)的浓度淬灭点为y=0.1;通过改变Dy~(3+)掺杂浓度或改变激发光的波长,均可实现发射光的颜色可调;在Tm~(3+)-Dy~(3+)离子之间存在能量传递。当Dy~(3+)掺杂浓度(物质的量分数)为0.15时能量传递效率达75.14%,能量传递机制为电偶极-电偶极相互作用。 相似文献
11.
Summary Two different methods were used to determine the separation factor α at different temperatures and the Gibbs-Helmholtz parameters
(Δ(ΔH), Δ(ΔS)) of two adjacent benzodiazepines on a chromatogram were obtained from plots of lnα versus 1/T. We first studied each factor (fraction of water ϕ in the ACN/water mixture and column temperatureT), which controls the retention mechanism, and then we examined the simultaneous variation of all these factors. The changes
in Δ(ΔH) and Δ(ΔS) in relation to a volume fraction of water ϕ in an ACN/water mixture were examined. In the ACN/water system, Δ(ΔH) was fairly constant in the acetonitrile region of ϕ≤0.52 and appears to be a roughly linear function of ϕ for ϕ≥0.52. In
this system Δ(ΔS) is approximately a parabolic function of ϕ with an optimum at ϕ≊0.52. The retention mechanism of ten benzodiazepines was
found to be significantly different in the methanol/water and ACN/water mixtures. The separation optimization of these ten
benzodiazepines was then considered. A fraction of water of 0.43 in the ACN/water mixture and a column temperature of 44 °C
gave the most efficient separation conditions in the ACN/water mixture. 相似文献
12.
Thermodynamic stability of CdMoO4 was determined
by measuring the vapor pressures of Cd and MoO3 bearing
gaseous species. Th vaporization reaction could be described as CdMoO4(s)+MoO2(s)
=Cd(g)+2/n(MoO3)n
(n=3, 4 and 5). The vapor pressures of
the cadmium (p
Cd)
and trimer (p
(MoO3)3)
measured in the temperature range 987≤T/K≤1111
could be expressed, respectively, as ln (p
Cd/Pa)
= –32643.9/T+29.46±0.08 and
ln(p
(MoO3)3/Pa) = –32289.6/T+29.28±0.08. The standard molar Gibbs free
energy of formation of CdMoO4(s),
derived from the vaporization results could be expressed by the equations:
°f
G
CdMoO4
(s)
0= –1002.0+0.267T±14.5 kJ mol–1
(987≤T/K≤1033) and °f
G
CdMoO4 (s)
0
= –1101.9+0.363T±14.4 kJ mol–1
(1044≤T/K≤1111). The standard enthalpy
of formation of CdMoO4(s)
was found to be –1015.4±14.5 kJ mol–1
. 相似文献
13.
M. G. Myskiv E. A. Goreshnik V. K. Pecharskii V. V. Oljinik 《Journal of Structural Chemistry》1994,35(1):82-86
We have carried out synthesis and X-ray structural study (DARCH, MoKα radiation, graphite monochromator, ϕ/2ϕ, scan mode, 2ϕ<-65°) of the CuNo3·C6H11N π-complex (a=14.346(6), c=16.719(7) δA, space group I41/a, and Z=16). The bifunctional (bridge and chelate) tridentate molecule of diallylamine cross-links the inorganic component
into infinite spirals oriented along the axes 41 and 43. The mainly covalent character of the Cu+...No
3
-
bond affects the hydrogen bond strength and the efficiency of the metal-olefin interaction.
I. Franko Lvov State University. Translated fromZhumal Strukturmoi Khimii, Vol. 35, No. 1, pp. 90–94, January–February, 1994.
Translated by T. Yudanova 相似文献
14.
Vladimir V. TretyakovRID=""ID="" To whom correspondence should be addressed Sergey V. Kazakov Alexander V. Bobyl Samuil G. Konnikov 《Mikrochimica acta》2000,132(2-4):365-375
An analytical model of an effective atomic number, Z
eff, for simultaneous calculation of composition and thickness of films on substrates that allows for backscattering processes
is presented. Comparison of dependencies of ϕ(ρz) parameters for film elements on electron beam energy, on atomic numbers of a film and a substrate and on film thickness
was done. The errors inherent in EPMA have been determined by comparing experimental data obtained on YBa2Cu3O7−x bulk crystals with model calculations. Possibility of EPMA as an effective technique for investigation of spatially inhomogeneous
objects was demonstrated by studying the correlation between composition and local superconducting properties (values of critical
temperature and critical current) of these films. 相似文献
15.
A number of samples of sodium and silver phosphate glasses doped with
various compositions of some transition metals viz. iron, manganese and zinc
chlorides alongwith undoped samples of sodium and silver phosphate glasses
were synthesized and characterized by X-ray diffraction, IR spectral, electrical
conductivity and differential scanning calorimetry (DSC). The glass transition
temperature (T
g)
and crystallization temperature (T
c)
values obtained from DSC curves were found to increase with increasing concentration
of the dopant Fe/Mn/Zn chlorides in both sodium and silver phosphate glasses
and the following sequence is observed:
T
g(–FeCl3)>T
g(–MnCl2)>T
g(–ZnCl2)
T
c(–FeCl3)>T
c(–MnCl2)>T
c(–ZnCl2)
The increase in T
g
and T
c values indicate
enhanced chemical durability of the doped glasses. The electrical conductivity
values and the results of FTIR spectral studies have been correlated with
the structural changes in the glass matrix by the addition of different transition
metal cations as dopants. 相似文献
16.
The method of momentum electron density for interatomic interactions has been applied to the two lowest σ states of the H
2
+
system. For attractive (1sσg) and repulsive (2pσ
u
) interactions, the behaviour of momentum density and its effect on the stabilization energy of the system are examined quantitatively.
The concept of contraction and expansion of the momentum density is shown to form an important guiding principle in this approach.
The origin of covalent bonding is discussed based on the energy partitioning proposed previously. 相似文献
17.
Microcalorimetric Study of the Oscillating Extraction System 总被引:3,自引:0,他引:3
Z. Honglin Y. Xiufang L. Xiangyang S. Haitao N. Yi W. Lili L. Chengxue 《Journal of Thermal Analysis and Calorimetry》2002,68(3):931-936
The power–time curves of the oscillating extraction system were determined at different temperatures for the extraction of
hydrochloric acid and acetic acid with primary amine N1923 (R–CH(NH2)–R1), R, R
1 represent alkyl of C9–11 in chloroform using the titration microcalorimetric method. The apparent activation energy was calculated from the induction
period (t
in), the first oscillation period (t
p.1) and the second oscillation period (t
p.2).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
18.
In this paper, evaluation of kinetic parameters (the activation energy – E,the pre-exponential factor – A and the reaction order – n) with simultaneous determination of the possible reaction mechanism of thermal decomposition of calcium hydroxide (portlandite),
Ca(OH)2 formed during hydration of commercial Portland-slag cement, by means of differential scanning calorimetry (DSC) in non-isothermal
conditions with a single heating–rate plot has been studied and discussed. The kinetic parameters and a mechanism function
were calculated by fitting the experimental data to the integral, differential and rate equation methods.
To determine the most probable mechanism, 30 forms of the solid-state mechanism functions, f(αc) have been tried. Having used the procedure developed and the appropriate program support, it has been established that the
non-isothermal thermal decomposition of calcium hydroxide in the acceleratory period (0.004<αc<0.554) can be described by the rate equation: d αc/dT=A/βexp(−E/RT)f(αc), which is based on the concept of the mechanism reaction:f(αc)=2(αc)1/2.
The mechanism functions as well as the values of the kinetic parameters are in good agreement with those given in literature.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
19.
N. M. Klimenko E. A. Rykova M. L. McKee I. N. Senchenya 《Russian Chemical Bulletin》1999,48(3):417-427
Ab initio MP2/6-31G*//HF/6-31G*+ZPE(HF/6-31G*) calculations of the potential energy surface in the vicinity of stationary points and the pathways of intramolecular rearrangements
between low-lying structures of the OBe3F3
+ cation detected in the mass spectra of μ4-Be4O(CF3COO)6 were carried out. Ten stable isomers with di- and tricoordinate oxygen atoms were localized. The relative energies of six
structures lie in the range 0–8 kcal mol−1 and those of the remaining four structures lie in the range 20–40 kcal mol−1. Two most favorable isomers, aC
2v isomer with a dicoordinate oxygen atom, planar six-membered cycle, and one terminal fluorine atom and a pyramidalC
3v isomer with a tricoordinate oxygen atom and three bridging fluorine atoms, are almost degenerate in energy. The barriers
to rearrangements with the breaking of one fluorine bridge are no higher than 4 kcal mol−1, except for the pyramidalC
3v isomer (∼16 kcal mol−1). On the contrary, rearrangements with the breaking of the O−Be bond occur with overcoming of a high energy barrier (∼24
kcal mol−1). A planarD
3h isomer with a tricoordinate oxygen atom and linear O−Be−H fragments was found to be the most favorable for the OBe3H3
+ cation, a hydride analog of the OBe3F3
+ ion; the energies of the remaining five isomers are more than 25 kcal mol−1 higher.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 420–430, March, 1999. 相似文献
20.
S. P. Chen X. X. Meng Q. Shuai B. J. Jiao S. L. Gao Q. Z. Shi 《Journal of Thermal Analysis and Calorimetry》2006,86(3):767-774
A
solid complex Eu(C5H8NS2)3(C12H8N2) has been obtained from reaction of
hydrous europium chloride with ammonium pyrrolidinedithiocarbamate (APDC)
and 1,10-phenanthroline (o-phen⋅H2O)
in absolute ethanol. IR spectrum of the complex indicated that Eu3+
in the complex coordinated with sulfur atoms from the APDC and nitrogen atoms
from the o-phen. TG-DTG investigation provided
the evidence that the title complex was decomposed into EuS.
The
enthalpy change of the reaction of formation of the complex in ethanol, Δr
H
m
θ(l), as –22.214±0.081 kJ mol–1,
and the molar heat capacity of the complex, c
m,
as 61.676±0.651 J mol–1 K–1,
at 298.15 K were determined by an RD-496 III type microcalorimeter. The enthalpy
change of the reaction of formation of the complex in solid, Δr
H
m
θ(s), was calculated as 54.527±0.314 kJ mol–1
through a thermochemistry cycle. Based on the thermodynamics and kinetics
on the reaction of formation of the complex in ethanol at different temperatures,
fundamental parameters, including the activation enthalpy (ΔH
≠
θ),
the activation entropy (ΔS
≠
θ),
the activation free energy (ΔG
≠
θ),
the apparent reaction rate constant (k),
the apparent activation energy (E), the
pre-exponential constant (A) and the reaction
order (n), were obtained. The constant-volume
combustion energy of the complex, Δc
U,
was determined as –16937.88±9.79 kJ mol–1
by an RBC-II type rotating-bomb calorimeter at 298.15 K. Its standard enthalpy
of combustion, Δc
H
m
θ,
and standard enthalpy of formation, Δf
H
m
θ,
were calculated to be –16953.37±9.79 and –1708.23±10.69
kJ mol–1, respectively. 相似文献