共查询到20条相似文献,搜索用时 15 毫秒
1.
《Chemical physics letters》1985,117(1):22-28
Comparison of open-shell RHF CNDO/S (CI) computations with existing optical and photoelectron spectra of the trans-stilbene radical cation indicates a significant structural relaxation subsequent to ionization. 相似文献
2.
The photoelectron spectrum of formaldoximie, CH2NOH, has been re-investigated with higher resolution and interpreted by, means of ab initio SCF Cl calculations. Calculations have confirmed that the states increase in energy as π1 < n1 < π2 < n2 and have shown the existence of a shake-up peak at ≈15 eV. The calculation of Franck-Condon factors allowed the interpretation of the observed vibrational structure. 相似文献
3.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1994,50(8-9):1475-1485
The Raman and transient resonance Raman spectra of biphenyl (BP) and its perdeuterated analogue (BP-d10) in three different electronic states (S0, S1 and T1) and in two different ionized states (cation and anion) have been recorded in solution. The S0 Raman spectra have also been measured for the crystalline state. The obtained set of spectra are analysed on the basis of the established vibrational assignments for the ground state of the planar (crystal) and the non-planar (solution) structures. The analysis suggests that BP in solution exists as a twisted structure in the S1 state, but that it takes planar or nearly planar structures in the T1, the cationic and the anionic states. 相似文献
4.
Richard W. Bigelow 《Chemical physics letters》1983,100(5):445-449
The low-lying doublet states of the p-quinodimethane (1) 3,7-dimethyl-p-quinodimethane (2) and tetracyano-p-quinodimethane (TCNQ) (3) cations are addressed within the semi-empirical open-shell RHF CNDO/S(Cl) formalism. Results indicate that the reduced intensity observed experimentally for the third ionization in both 1 and 2 arises from a pronounced configuration mixing between the parent one-electron Koopmans state and the non-Koopmans HOMO → LUMO valence excitation. Similar contributions are found to account for the relative intensifies of the first and second ionization bands (1.0 : 1.425) in 3. 相似文献
5.
N-Methyl and N-ethylphenothiazines were oxidized with bromine and sodium perchlorate to give stable cation radical salts. Their well-resolved epr spectra were obtained in nitromethane solution. In order to assign the hfs constants, the cation radicals of N-deuteriomethyl and N-deuterioethylphenothiazines were prepared with lead tetraacetate and trifluoroacetic acid in solutions. 相似文献
6.
Eshimbetov AG Kristallovich EL Abdullaev ND Tulyaganov TS Shakhidoyatov KhM 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,65(2):299-307
A detailed analysis of both frontier MOs and electronic transitions in UV spectra of 16 4-quinazolinone derivatives has been carried out in MO terms, by semiempirical methods AM1/CI, CNDO/S and ZINDO/S. On the basis of experimental and theoretical investigations by the ZINDO/S and CNDO/S methods the long-wavelength bands of 4(3H)-quinazolinone and its derivatives have been assigned to n-->pi(*) transition of the CO fragment and to the transition caused by intramolecular charge transfer from Ph and NCN fragments to CO group. It was shown that theoretically obtained electronic transitions applying method AM1/CI are not in agreement with experimental data observed for the 4(3H)-quinazolinone and 2,4(1H,3H)-quinazolinedione. Good correlation of theoretical and experimental data has been obtained by the method ZINDO/S for the wavelengths and the molar extinction coefficients of the compounds studied. Satisfactory correlation of theoretical and experimental data has also been obtained by the method CNDO/S with singly and doubly excited configurations, for the wavelengths only. Such correlations on experimental and theoretical wavelength and molar absorption coefficients of 4-quinazolinone derivatives are carried out for the first time. 相似文献
7.
The lowest doublet electronic state of the cyclopentadienyl radical (CPDR) and the lowest singlet state of the cyclopentadienyl cation (CPDC) are distorted from the highly symmetric D(5h) structure due to the Jahn-Teller effect. A valence bond analysis based on the phase-change rule of Longuet-Higgins reveals that in both cases the distortion is due to the first-order Jahn-Teller effect. It is shown that, while for the radical an isolated Jahn-Teller degeneracy is expected, in the case of the cation the main Jahn-Teller degeneracy is accompanied by five satellite degeneracies. The method offers a chemically oriented way for identifying the distortive coordinates. 相似文献
8.
We report Xα SW MO calculations on (η2-C4H4)Fe(CO)3 and its five transition states, formed by removing a half of an electron from each of the five uppermost filled MOs. Eigenvalues in the transition states depend only slightly upon the MO from which the “high-ionization” occurs. The MOs are more polarized in the transition states than in the ground state. The C4H4-Fe bonding is highly covalent. 相似文献
9.
Non-empirical SCF and CI calculations are reported for the HN2, free radical in various low-lying electronic states. The nature of the angular and N-N and N-H stretching potential curves of each of these species is investigated, including a study of the dissociative behavior of such states. The ground state is found to be only very slightly bound with respect to NH stretch, in contrast to what is observed for isoelectronic HCO, The vertical electronic spectrum of HN2, appears to be marked by a single long wavelength transition (1.95 eV) from the bent (124°) ‘A’ ground state to the linear 2Π excited species, but at least four other intra-valence and an additional n → 3s Rydberg species are indicated in the 5.5–8.0 eV absorbing region. 相似文献
10.
Wang Chan John L. Courtneidge Alwyn G. Davies Jeffrey C. Evans Anthony G. Neville Christopher C. Rowlands 《Tetrahedron letters》1985,26(34):4121-4124
A revised interpretation is proposed for the 1H and 13C hyperfine coupling in the e.s.r. spectrum of the tetra-1-adamantylcyclobutadiene radical cation, and assumes that free rotation occurs about the 1-adamantyl bond. 相似文献
11.
《Chemical physics letters》1985,115(2):154-157
Core-level photoelectron spectra of geometrical isomers of nitroanilines are studied by a semi-empirical method. Energy results alone reveal the presence of satellites for the ionization from the NO2 group in all three isomers, in contrast to some experimental observations. Intensity calculations, using HOMOLUMO overlap, agree with the calculation using full π-overlap for para-nitroaniline, but differ considerably for meta- and ortho-nitroanilines. 相似文献
12.
Dora Demeter Philippe Blanchard Ion Grosu Jean Roncali 《Journal of inclusion phenomena and macrocyclic chemistry》2008,61(3-4):227-239
The association of linear or macrocyclic polyethers with the electronic properties of the π-conjugated polythiophene backbone leads to functional conducting polymers that exhibit metal cation dependent electronic properties. Based on this concept, various classes of cation sensors have been proposed and investigated for almost two decades. The interactions of metal cations with linear or macrocyclic polyether functional groups lead to modifications of the electronic properties of the π-conjugated backbone through various mechanisms including direct electronic effects on a single conjugated chain, collective electrochemical processes, or conformational changes. Conjugated polymers and oligomers representative of these various processes are discussed with an emphasis on recent examples of derivatized conjugated systems in which the interactions between metal cations and polyether groups serve as driving force to create molecular motion in conjugated systems. 相似文献
13.
The photoelectron spectra of ruthenium tetroxide and osmium tetroxide excited by He(I) radiation are reported. From their interpretation it follows that the first two strong low energy transitions in the electronic absorption spectra of OsO4, RuO4, TcO?4, ReO?4, MoO2?4 and WO2?4 can be assigned to t1 → 2e and 3t2 → 2e respectively. 相似文献
14.
We report simulated photoelectron spectra for 1,2,3-triazolide (CH)(2)N(3)(-), which reveal the vibronic energy levels of the neutral radical 1,2,3-triazolyl, (CH)(2)N(3). The spectral simulation using a quasidiabatic Hamiltonian H(d) comprised of polynomials through 4th order (thereby extending conventional quadratic expansions), is compared to both the experimental spectrum and a standard Franck-Condon (adiabatic) simulation. The quartic H(d) is far superior to the quadratic H(d), reproducing the main features of the experimental spectrum and allowing for their subsequent assignment. The contributions from excited anion states successfully reproduce the observed vibronic transitions to the red of the assigned band origin of the neutral species. The algorithmic extensions required for the determination of these hot band contributions to the total spectrum are discussed. Convergence of the spectral envelope with respect to the vibronic basis, including both the principal and hot bands, required more than 10(9) terms. 相似文献
15.
A procedure is outlined for the calculation of molecular static electric polarizabilities in excited singlet and triplet states using the ”finite perturbation theory“ in conjunction with the CNDO/S CI method. Numerical results for the ground and the three lowest excited singlet and triplet states of naphthalene are presented. It turns out that the generalized Hellmann-Feynman theorem is approximately valid for the CNDO/S CI wavefunctions and that triplet and singlet state polarizabilities in states of the same symmetry may strongly differ. 相似文献
16.
17.
Coupled-cluster and density-functional methods have been used to determine specific rotations and electronic circular dichroism (ECD) rotational strengths for (S)-2-chloropropionitrile. Coupled-cluster specific rotations using both the length- and velocity-gauge representations of the electric-dipole operator, computed with basis sets of triple-zeta quality containing up to 326 functions, compare very well with recently reported gas-phase cavity-ring-down polarimetry data. ECD rotational strengths for the six lowest-lying excited states are found to vary in sign, and the second excited state, which has a larger rotational strength than the first by a factor of 4, was found to yield a much larger contribution (by a factor of 10) to the overall negative specific rotation observed both experimentally and theoretically. However, both valence and Rydberg states appear to make substantial contributions to the total rotation, often of opposite sign from the converged/linear-response result. Furthermore, the sum-over-states approach was found to be inadequate for reproducing the specific rotations derived from the linear-response approach, even when 100 excited states (well beyond the estimated ionization limit) were included in the summation. Density-functional specific rotations using the B3LYP functional with basis sets of quadruple-zeta quality containing up to 588 functions are found to be too large compared to experiment by approximately a factor of 2. This error appears to be related to both the underestimation of the electronic excitation energies, as well as concomitant overestimation of the corresponding ECD rotational strengths. Although earlier studies reported good agreement between density-functional specific rotations and experiment when electric-field-dependent functions were used in conjunction with a double-zeta-quality basis set, the results reported here, which are near the basis-set limit, suggest that this agreement may be fortuitous. 相似文献
18.
Valence-band angle-resolved photoelectron spectra of oriented polycrystalline films of hexatriacontane (n-C36H74) were measured by He II (40.8 cV) light. Significant dependence of the spectra on photoemissive angle and light-incidence angle was observed. The advantages and problems of angle-resolved UV photoelectron spectroscopy to the study of electronic structures of organic crystals are discussed. 相似文献
19.
The 30.4 nm He(II) photoelectron spectra of the fluorosubstituted ethylenes have been recorded. The assignment of all main bands is obtained from many-body Green's function calculations. The results from the semi-empirical HAM/3 method lead to a nearly identical assignment. For the mono- and difluoroethylenes, an unambiguous interpretation of the spectra can be established from empirical considerations alone. The set of spectra has been reexamined with respect to the “perfluoro-effect” rules. Also discussed are the ionisation energies as a function of the geminal FCF bonding angle and the similarity of the spectra of the cis and trans isomers of 1,2-difluoroethylene. Additional weak bands were detected in the energy region 21–24 eV in all spectra and were attributed to “shake-up” transitions on the basis of 2ph-Tamm-Dancoff Green's function calculations. The orbital model of ionisation breaks down for the ionisation out of the F(2s) and C(2s) orbitals in general. The calculations reveal a charge transfer character of the excitations accompanying ionisation from the C(2s) orbitals. 相似文献
20.
B.J. Brisdon G.F. Griffin J. Pierce R.A. Walton 《Journal of organometallic chemistry》1981,219(1):53-59
The W 4f binding energies of various carbonyl-containing complexes of tungsten are reported. Comparisons between WII complexes containing the [(η3-allyl)W(CO)2] moiety and neutral derivatives of the type W(CO)6-xLx are made. The absence of a clear-cut correlation between the W 4f binding energies and the value of x in W(CO)6-xLx is discussed and these results compared with those obtained for the analogous molybdenum complexes. 相似文献