Photoelectron and ultraviolet absorption spectra of allenyl vinyl ethers

The electronic structure of allenyl vinyl ethers (I) has been studied with the aid of photoelectron and UV spectroscopy, as well as MNDO and CNDO/S quantumchemical calculations. Divinyl ether has been selected as a model system for these molecules. The photoelectron spectra of I are similar to the spectrum of divinyl ether, with the exception of the band at 10.2–10.6 eV. The long-wavelength band in the UV spectra of I has been assigned to a transition localized in the allene group. The short-wavelength band of I corresponds to the ^* transition observed in divinyl ether.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2011–2014, September, 1989.     

Photoelectron spectroscopy of naphthacene crystal in the vacuum ultraviolet region

The energy distribution curves of the photoelectrons emitted from naphthacene (C₁₈H₁₂) crystal in the vacuum ultraviolet region were measured by an ac modulated retarding potential method. The peaks in the curves, 5.8₃, 7.2₈, 8.2₉, 8.7₀ and 9.4₀ eV, are considered to be associated with the valence bands of the naphthacene crystal.     

The vacuum ultraviolet spectra of methylated silanes

The vacuum ultraviolet spectra of monomethylsilane, monomethylsilane-d₃, dimethylsilane, dimethylsilane-d₂, trimethylsilane, trimethylsilane-d₁, trimethylmonofluorosilane and tetramethylsilane have been recorded in the range 135 nm to 190 nm.     

Rydberg series in the absorption spectra of H2O and D2O in the vacuum ultraviolet

The photoabsorption cross section of molecular H₂O and D₂O has been determined in the range from hν = 10eV to 20 eV with 0.03 Å resolution. A refined analysis of the Rydberg series including the rotational line shapes of several bands to locate the band origins and a comparison with recent ab initio calculations is given. In the region of continuous absorption we have assigned a p-type and an s-type Rydberg series leading to the ²A₁ and the ²B₂ state respectively with quantum defects δ ≈ 0.75 and δ ≈ 1.36.     

The vacuum ultraviolet spectra of fluorine chlorine substituted trivalent phosphorus

The vapor phase absorption spectra of PF₃, PF₂Cl, PFCl₂, and PCl₃ are reported in the vacuum ultraviolet spectral region 2400—1200 A. These results are compared with information obtained from photoelectron spectra. A brief discussion of the spectra in terms of analogous absorption regions and results from CNDO/2 calculations are given.     

Photoelectron spectra of cyclopolysilanes

Summary He (I) PE spectra of cyclopentasilane and cyclohexasilane show excellent agreement with STO-3 G + ab initio calculations. The HOMO in both compounds is of (SiSi) 3 p character. First IP's appear at 9.4 and 9.6 eV respectively.

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Photoelektronenspektren von Cyclopolysilanen (Kurze Mitt.)

Zusammenfassung Die He (I) PE-Spektren der Cyclosilane Si₅H₁₀ und Si₆H₁₂ zeigen ausgezeichnete Übereinstimmung mit STO-3 G + ab initio Rechnungen. Beide Ringe besitzen HOMO's mit (SiSi) 3 p Charakter. Die ersten Ionisierungspotentiale liegen bei 9.4 bzw. 9.6 eV.

     

Photoelectron spectra of 1,4-benzodiazepines

Photoelectron (PE) spectra of 20 biologically active molecules of 1,4-benzodiazepine derivatives have been measured. The spectra in the range of low ionization energies (IE) were interpreted by comparison of MNDO quantum-chemical calculation data with the perturbation theory estimations. The effect of substituents and structural changes in the series studied is felt mainly by the -MOs of ring A; theortho effect is observed in the PE spectra ofortho isomers.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1583–1587, September, 1993.     

Absorption spectra of volatile aromatic hydrocarbon films in the vacuum ultraviolet region

Absorption spectra of volatile aromatic hydrocarbon films, p-terphenyl, chrysene, benzanthracene and triphenylene, in the near and vacuum ultraviolet region down to 130 nm were measured under an atmosphere of Ar gas to suppress their sublimation. The spectrum of p-terphenyl is different from the spectra reported for other phases. This difference is explained in terms of the change of dihedral angles among the three benzene rings. The peak positions in the spectra of chrysene and bezanthracene agree with those in the solution spectra. The differences in the peak intensities are discussed in terms of the orientation of the films with the aid of MO calculations. The result of triphenylene suggests the presence of Davydov splitting.     

Photoelectron spectra of substituted benzenes

Photoelectron spectra of several substituted dimethylanilines, nitrobenzenes, acetophenones and nitrosobenzenes have been studied with a view to examine the electronic effects of substituents on the various φ and n levels. The results are discussed in the light of molecular orbital calculations and electronic absorption spectra. Correlation of substituent effects on the IE's with π-electron densities and Hammett substituent constants has enabled rationalization of all available data on mono- and disubstituted benzenes. The IE's generally increase with the electron-withdrawing power of the substituents.     

Photoelectron spectra of vinyl tellurides

The lowest energy band in the photoelectron (PE) spectra of alkyl vinyl tellurides is attributed to-MO with predominant contribution from the p_z-AO of the tellurium atom. The second and fourth lowest energy bands correspond to-MO. An additional-MO is located between these-MO. The introduction of a second vinyl group hardly affects the HOMO. The heterocyclization of divinyl telluride has a large perturbation effect. Nevertheless, divinyl telluride and tellurophene have the same type of orbital structure.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 935–939, April, 1991.     

Photoelectron spectra and steric structure of sulfenamides

According to the data from photoelectron and UV spectroscopy, the molecules of N,N-dimethylmethane sulfenamide and N,N-diethylpropane-2-sulfenamide have a conformation with orthogonal orientation of n_N and n_S orbitals, while N,N-dimethylbenzene sulfenamide in the gas phase exists in conformational equilibrium of the planar and skewed conformers.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 77–80, January, 1990.We would like to thank F. G. Nasybullina for conducting the GLC analysis.     

Photoelectron spectra and ion chemistry of imidazolide

The 351.1 nm photoelectron spectrum of imidazolide anion has been measured. The electron affinity (EA) of the imidazolyl radical is determined to be 2.613 +/- 0.006 eV. Vibrational frequencies of 955 +/- 15 and 1365 +/- 20 cm(-1) are observed in the spectrum of the (2)B1 ground state of the imidazolyl radical. The main features in the spectrum are well-reproduced by Franck-Condon simulation based on the optimized geometries and the normal modes obtained at the B3LYP/6-311++G(d,p) level of density functional theory. The two vibrational frequencies are assigned to totally symmetric modes with C-C and N-C stretching motions. Overtone peaks of an in-plane nontotally symmetric mode are observed in the spectrum and attributed to Fermi resonance. Also observed is the photoelectron spectrum of the anion formed by deprotonation of imidazole at the C5 position. The EA of the corresponding radical, 5-imidazolyl, is 1.992 +/- 0.010 eV. The gas phase acidity of imidazole has been determined using a flowing afterglow-selected ion tube; delta(acid)G298 = 342.6 +/- 0.4 and delta(acid)H298 = 349.7 +/- 0.5 kcal mol(-1). From the EA of imidazolyl radical and gas phase acidity of imidazole, the bond dissociation energy for the N-H bond in imidazole is determined to be 95.1 +/- 0.5 kcal mol(-1). These thermodynamic parameters for imidazole and imidazolyl radical are compared with those for pyrrole and pyrrolyl radical, and the effects of the additional N atom in the five-membered ring are discussed.     

Absorption spectra in the vacuum ultraviolet region of small molecules in condensed phases

With radiation from a synchrotron we measured the spectra of several small molecular species, in the solid phase at 10K, either pure--O2, NO, CO2, N2O, H2O and NH3--or, for NH3, also dispersed in Ar at molar ratio 1/250, from the onset of absorption in the ultraviolet region until the limits of transmission by crystalline LiF or solid Ar. In a quantitative treatment of spectral data, we fitted the total absorption profile divided by wavenumber to Gaussian curves of minimal number, and made tentative assignments of electronic transitions and vibrational structure by comparison with spectra of gaseous species. These results illuminate the nature of electronic spectra of samples in solid phases in the vacuum ultraviolet region.     

Photoelectron spectra of planar sulfur heterocycles

The photoelectron spectra of benzo[b]thiophene (2), benzo[c]thiophene (3), thieno[3,2-b] thiophene (4) and thieno[2,3-b]thiophene (5) together with 2,1,3-benzothiadiazol (6) and benzofurazan (7) have been recorded and the first three bands have been assigned to π-orbitals on the basis of band shapes and semiempirical calculations. The good agreement obtained between measured and calculated ionization potentials suggests that sulfur 3d orbital participation must be very small.     

Photoelectron spectra of the allyl amines

The Hel photoelectron spectra of the three allyl amines show low ionization potential bands arising from nitrogen lone-pair n electrons and ethylenic π-bond electrons. Analysis of the spectra using MINDO/3 calculations and comparisons with ionization data of related molecules shows that π-π interactions are considerable, but n-π interactions are small. The π-π splitting in triallyl amine is consistent with a near-planar C₃ symmetry structure for the gas phase molecule.