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1.
A. N. Egorochkin S. E. Skobeleva T. G. Mushtina E. T. Bogoradovsky 《Russian Chemical Bulletin》1998,47(8):1526-1531
The integrated extinction coefficients (A) of the C≡C stretching modes in the IR spectra of 12 germylacetylenes Me3GeC≡CR are determined by the resonance interactions of substituents with the triple bond. TheA
1/2 values change linearly with change in the difference between the effective π-electron charges on the atoms at the triple
bond and σ0
R constants of organic substituents R. The average value of the σ0
R constant of the Me3Ge substituent in the compounds studied is +0.06. The resonance acceptor effect of the Me3Ge substituent toward the triple bond (d,π-conjugation) is stronger than the donor effect (σ,π-conjugation).
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1569–1574, August, 1998. 相似文献
2.
A. N. Egorochkin S. E. Skobeleva T. G. Mushtina E. T. Bogoradovsky 《Russian Chemical Bulletin》1997,46(1):71-75
A comparative study of the integrated extinction coefficients (A) of the C≡C stretching bands in the IR spectra of acetylene derivatives Me3SiC≡CR, HC≡CR, and Me3CC≡CR was carried out. The resonance interactions of substituents with a triple bond are the main cause of the changes in
the values ofA. The total resonance effect of the Me3Si fragment involves both acceptor (d, π-conjugation) and donor (σ, π-conjugation) components; d, π-conjugation dominates
in the silylacetylenes studied. Theσ
R
0
resonance constant of the Me3Si substituent in compounds Me3SiC≡CR is 0.17±0.02.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 76–80. January 1997. 相似文献
3.
S. E. Skobeleva T. G. Mushtina A. N. Egorochkin M. M. Demina A. S. Medvedeva M. G. Voronkov 《Russian Chemical Bulletin》1998,47(9):1710-1713
The σR0 and σp parameters of Me3SiOCR2 and HOCR2 substituents at the triple bond were determined using the IR spectra of individual acetylene derivatives and their H-complexes.
These parameters vary as the effective charge on the atoms of the C≡C fragment of terminal acetylenic alcohols and their trimethylsilyl
ethers changes due to intermolecular interaction. The most reliable values of σR0 and σp parameters (−0.02 and −0.03, respectively) for the Me3SiOCH2 substituent were established; they indicate a sharp decrease in σ,π-conjugation of the Me3SiOCH2 substituent with the triple bond as compared to the Me3SiCH2 substituent.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1759–1762, September, 1998. 相似文献
4.
Unlike theE
HOMO energies, the first vertical ionization potentials (I
1) of monosubstituted ethylenes dependen not only on both the inductive and resonance effects but also on the polarizability
of the substituents, which can be characterized by the σα parameters. The σ
R
+
, σ
p
+
, and σα parameters for 12 silicon-, germanium-, and tin-containing groups were determined using the equations relating theI
1 values and the σI, σ
R
+
, σ
p
+
and σα parameters of the substituents in the molecules of organic compounds. The conjugation of organoelemental substituents with
the double bond is stronger than that with benzene ring; the σ
R
+
parameters in the ethylene and benzene series are related by a linear dependence.
Translated fromIzvestiya Akademii Nauk Seriya Khimicheskaya, No. 9, pp. 1626–1631, September, 1997. 相似文献
5.
The first vertical ionization potentialsl
1 of molecules RπX (X=Ph, H2C=CH, and HC≡C) depend on the joint influence of the inductive, resonance, and polarizability effects of substituents X, which
are characterized by parameters σ1, σR+, and σα, respectively. The mechanism of conjugation in radical cations formed upon ionization of RπX is changed as compared to neutral RπX molecules, while the substituent X becomes polarized. The conjugation and polarizability effects are strenthened in the
sequence Ph < H2C=CH <HC≡C as Rπ changes from Ph to H2C=CH and HC≡C. The σR+ parameters of Si-, Ge-, and Sn-containing substituents X are dependent on the type of Rπ but are connected by linear dependences in the series of benzene, ethylene, and acetylene derivatives.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1481–1486, August, 1998. 相似文献
6.
The results of MNDO/PM3 calculations of η5-π-C60R5M complexes (R=H and Ph; M=Tl and In) are reported. Local energy minima and geometric parameters as well as the heats of formation
and ionization potentials were determined for all systems in question. The nature of chemical M—pent bonding (pent is the pentagonal face) is discussed. The results of calculations are compared with experimental data that confirm our predictions
about the possibility of existence of stable cyclopentadienyl type η5-π-complexes of C60 fullerence derivatives. The stability of the C60In12 complex with theI
h
symmetry, in which the In atoms are coordinated to each of 12 pentagonal faces of C60 fullerene, was estimated. The energy of the In—pent bond (62.4 kcal mol−1) is close to that in C60H5In (64.5 kcal mol−1).
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1935–1940, November, 1997. 相似文献
7.
The CEPA-PNO method is used for calculating the energy difference ΔE
ST between the3∑− and the1Δ states of diatomic molecules in electronic π2 configurations. An analysis of the contribution of electron correlation to ΔE
ST is performed in terms of physically understandable effects such as direct correlation, dynamic spin polarization, semiinternal
and internal excitations. It is shown that these effects are of completely different importance for the molecules treated
in this study: For C2 the direct correlation between the two singly occupied π-orbitals is the dominant correlation contribution to ΔE
ST; for O2, S2, SO the internal excitation π
u
2
→ π
g
2
is predominant, whereas for NH and PH there is a close competition between the direct correlation and the spin polarization
of the underlying σ-orbitals. The basis set dependence of these effects is investigated, in particular for NH. Our final results
reproduce experimental values of ΔE
ST within 0.05–0.10 eV. 相似文献
8.
Solvolytic reactions could be greatly influenced by the presence of neighbouring groups. The tool of increasing electron demand
has been successfully used to detect such participation. For example, the tool has detected the presence of major π-participation
inanti-7-norbornenyl and π-conjugation in cyclohexen-2-yl derivatives. The changes observed in the absolute values ofp
+ with ring size in cyclic systems could be adequately explained by the I-strain concept. The tool has established major πδ-conjugation
in cyclopropylcarbinyl and nortricyclyl derivatives. πδ-participation in the Coates’ cation has been unambiguously established.
However, this sensitive probe has failed to provide evidence for δ-participation in the solvolysis of 2-norbornyl system.
It, is concluded that the tool of increasing electron demand is quite sensitive to detect the presence or absence or neighbouring
group participation. 相似文献
9.
The molecular and electronic structure of hypothetical complexes of unsubstituted fullerene C60 withI
h
symmetry and its cyclopentadienyl type derivatives were simulated by the MNDO/PM3 method taking the C60(XC[)
n
molecules (n=1, 2, 10, 12; X=Si, Ge, Sn) and η5-C60H5XCp (X=Ge, Sn), respectively, as example. The complexes 12η5-πC60(XCp)12 and η5-πC60XCp withI
h
andC
5v symmetry, respectively, were found to be the most stable compounds. The energies of the X−C60 bonds in these complexes are close to those of X−Cp bonds in bis(cyclopentadienyl) complexes XCp2 and are substantially higher than the energies of similar bonds in complexes of unsubstituted fullerene η1-πC60(XCp)− and η5-πC60(XCp)+. Geometric parameters and spin densities in radicals C60XCp and biradicals C60(XCp)2 and C60H10 were calculated.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2155–2165, November, 1998. 相似文献
10.
The effects of X substituents on the energies of charge-transfer bandshv
CT in electronic absorption spectra of charge-transfer complexes of π-, n-, or σ-donors (DX) with π- or σ-acceptors (A) as well
as on the ionization potentialsI
D of individual DX molecules are described by the equationhv
CT(l
D)=a +bσ1 +cσ
R
+
+dσα. When DX and A are fixed, the inductive (bσ1), resonance (cσ
R
+
), and polarization (dσα) contributions tohv
CT andI
D are virtually identical. The electronic structure of the D.+X donor component of the compact [A.−, D.+X] radical-ionic pair in a solution is similar to that of the radical cation generated upon photoionization of the individual
DX molecule in the gaseous phase.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1002–1006, June, 2000. 相似文献
11.
Maurizio Guerra 《Theoretical chemistry accounts》2000,104(6):455-460
Calculations with the density functional theory (DFT) method using the most popular functional, Becke's three parameter hybrid
with the Lee, Yang and Parr correlation functional, predict the π-delocalized configuration of the vinylacyl radical, CH2=CH—C(•)=O, to be more stable than the σ-localized configuration in contrast with ab initio unrestricted quadratic configuration
interaction with single and double excitations calculations as previously found for the isoelectronic vinyl radical, Y-C(•)=CH2, bearing π-type α substituents. Experimental evidence on the electronic configuration adopted by vinyl radicals is contrasting.
In the present case comparison with experiment indicates firmly that the currently available density functionals overestimate
the stability of π-delocalized versus σ-localized configurations in radicals since they favor the π configuration for the
γ-methylvinylacyl radical, CH3—CH=CH—C(•)=O, in contrast with unequivocal electron spin resonance data. This failure is mainly due to an incorrect estimate
of dynamic correlation energy with DFT functionals.
Received: 13 January 2000 / Accepted: 16 March 2000 / Published online: 21 June 2000 相似文献
12.
A. N. Egorochkin M. G. Voronkov S. E. Skobeleva T. G. Mushtina O. V. Zderenova 《Russian Chemical Bulletin》2000,49(1):26-32
The first vertical ionization potentialsI(ns) of 69 monosulfides XSY (X, Y=H, Hal, organic, or heteroorganic substituent) are related to the inductive σI resonance (σ
R
+
) and polarizability (σα) constants of the substituents by dependences of theI(nS)=a+bΣσI+bΣσR+bΣσα type. TheI(ns) values are also affected by hyperconjugation which increases on going from XSH to XSY (Y≠H) compounds. The first calculations
of the σ
R
+
parameters characterizing the conjugation of Si-, Ge-, Sn-, and Pb-containing substituents with the S.+ radical cation center are reported. The reasons for weakening of resonance donor properties of heteroorganic substituents
of the +M-type in the systems studied as compared to those of the same substituents in the corresponding aromatic radical cations are
considered.
Translated fromIzvestiya Akademii Nauk. Seriya Khmicheskaya, No. 1, pp. 25–31, January, 2000. 相似文献
13.
A. N. Egorochkin M. G. Voronkov S. E. Skobeleva T. G. Mushtina O. V. Zderenova 《Russian Chemical Bulletin》1990,49(1):26-32
The first vertical ionization potentialsI(ns) of 69 monosulfides XSY (X, Y=H, Hal, organic, or heteroorganic substituent) are related to the inductive σI resonance (σ
R
+
) and polarizability (σα) constants of the substituents by dependences of theI(nS)=a+bΣσI+bΣσR+bΣσα type. TheI(ns) values are also affected by hyperconjugation which increases on going from XSH to XSY (Y≠H) compounds. The first calculations
of the σ
R
+
parameters characterizing the conjugation of Si-, Ge-, Sn-, and Pb-containing substituents with the S.+ radical cation center are reported. The reasons for weakening of resonance donor properties of heteroorganic substituents
of the +M-type in the systems studied as compared to those of the same substituents in the corresponding aromatic radical cations are
considered.
Translated fromIzvestiya Akademii Nauk. Seriya Khmicheskaya, No. 1, pp. 25–31, January, 2000. 相似文献
14.
O. V. Shishkin O. Ya. Borbulevych I. V. Blokhin Yu. M. Atroschenko S. S. Gitis 《Russian Chemical Bulletin》1998,47(3):423-428
Potassium 10-methoxy-9-nitroanthracenide was studied by X-ray diffraction analysis. The central ring of the anthracene fragment
adopts an asymmetrically flattened boat conformation. The bond lengths in the C(Ar)−C(NO2)−C(Ar) fragment are indicative of the presence of conjugation between the π-systems of the benzene rings and the nitro group
owing to a substantial contribution of theaci form to the structure of the nitro group. Quantum-chemical calculations of anionic σ-complexes of 9-nitroanthracene derivatives
were performed. In all cases, the central ring adopts two conformations with the pseudoaxial and pseudoequatorial orientations
of the substituents at the saturated C(10) atom, respectively. The relative stability of the conformers and the factors determining
the stability were considered. The minima on the potential energy surface have a flattened shape in spite of relatively high
barriers to the conformational transition (2–4 kcal mol−1). The deviation of the C(Ar)−C(Ar)−C(sp3)−C(Ar) torsion angle from the equilibrium value by ±20° causes an increase in the energy of the anion by less than 1 kcal
mol−1. The effect of the substituents on the charge distribution was considered.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 438–443, March, 1998. 相似文献
15.
Relativistic energy-consistent small-core lanthanide pseudopotentials of the Stuttgart–Bonn variety and extended valence
basis sets have been used for the investigation of the dimers La2 and Lu2. It was found that the ground states for La2 and Lu2 are most likely 1∑
g
+ (σ
g
2π
u
4) and 3∑
g
− (4f
144f
14σ
g
2σ
u
2πu
2), respectively. The molecular constants including error bars were derived from multireference configuration interaction as
well as coupled-cluster calculations, taking into account corrections for atomic spin–orbit splitting as well as possible
basis set superposition errors. The theoretical values for La2 (R
e=2.70±0.03 ?, D
e=2.31±0.13 eV, ωe=186±13 cm−1) show good agreement with the experimental binding energy (D
e=2.52±0.22 eV), but the experimental vibrational constant in an Ar matrix (ωe=236±0.8 cm−1) is significantly higher. For Lu2 the theoretical values (R
e=3.07±0.03 ?, D
e=1.40±0.12 eV, ωe=123±1 cm−1) are in overall excellent agreement with experimental data (D
e=1.43±0.34 eV, ωe=122± 1 cm−1). The electronic structures of La2 and Lu2 are compared to those other lanthanide dimers and trends in the series are discussed.
Received: 25 March 2002 / Accepted: 2 June 2002 / Published online: 21 August 2002 相似文献
16.
The basicities of several 2′-, 3′-, and 4′-substituted 4-acetylbiphenyls and biphenyl-4-carboxylic acids have been determined
spectrophotometrically in sulphuric acid media at 30°C. The pKBH
+ of 3′- and 4′-substituted compounds are correlated by the Hammett equation. The 4′-methoxy group deviates considerably in
the Hammett plot. This is attributed to its conjugative interaction with the carbonyl or carboxyl group aided by protonation.
Good correlation exists between pKBH
+ and σ+. The basicities of 2′-substituted 4-acetylbiphenyls and biphenyl-4-carboxylic acids reaffirm the existence of π-electron
steric effect of 2′substituents. 相似文献
17.
Egorochkin A. N. Skobeleva S. E. Bogoradovsky E. T. Zubova T. P. 《Russian Chemical Bulletin》1994,43(6):976-982
The resonance donor effect of the , conjugation of R3M and R3MCH2 (M = Si, Ge, Sn; R is an alklyl group) substituents with the triple bond in compounds R3MC=CX and R3MCH2CCX (X = H, R) changes on passing from isolated molecules to their H-complexes. A partial + charge on the triple bond enhances , conjugation; a partial – charge on the triple bond has practically no effect on the resonance properties of R3M substituents, whereas the , conjugation of R3MCH2 substituents diminishes owing to the effect of negative direct resonance interaction. The effect of , conjugation on the effective negative charges of the carbon atoms in the -CC- fragments was estimated quantitatively.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1041–1046, June, 1994.This work was supported by the Russian Fundation for Basic Research (Grant 93-03-18372). 相似文献
18.
This paper deals with the mechanisms of localization of Franck-Condon vibronic coupling of πσ*- or πlπ*-orbital type in a few vibrational modes, (LVM) in excited electronic states of polyatomic molecules. The analysis of vibronic
coupling uses highly symmetric basis sets (for representing MO structures and normal coordinates ξR) as well as simplified models that relate the shift ΔR of the electron potential minima along the normal coordinates to the MO structure and to ξR in the form of analytical expressions. The modes that are active in LVM are determined from the experimental luminescence
spectra. These ideas about approximately high local symmetry of vibronic coupling in benzene fragments as well as the estimates
of ΔR depending on variations in the MO structure explain the experimental results.
L. Ya. Karpov Physicochemical Scientific Research Institute. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 2, pp. 286–291, March–April, 1995.
Translated by L. Smolina 相似文献
19.
20.
A. G. Mirochnik E. V. Gukhman V. E. Karasev P. A. Zhikhareva 《Russian Chemical Bulletin》2000,49(6):1024-1027
The fluorescence and photochemical properties of crystalline β-diketonatoboron difluorides (DBD) RCOCHCOR1BF2 were studied. These compounds are characterized by relatively high photochemical stability. The introduction of electron-donating
groups into the aromatic α-substituent of the chelate ring increases and the introduction of electron-withdrawing groups decreases
the fluorescence intensity of DBD. Anisoylbenzoylmethanotoboron difluoride was found to exhibit the highest fluorescence intensity.
The substituents were shown to influence the relative arrangement of singlet and triplet ηπ* and ππ* levels and luminescence properties of compounds.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1030–1033, June, 2000. 相似文献