Photoelectron spectra of p-terphenyl in gaseous and solid states

The high resolution photoelectron spectrum of gaseous p-terphenyl and the spectral response of its photoemission in solid state were measured. Both spectra - gaseous and solid - were in good agreement when a slight shift was assumed. The first vertical ionization potential in the gas phase was 8.20 eV and the potential obtained from the threshold value of the photoemission of crystalline p-terphenyl was 6.1 eV. The conformations in both phases were also discussed.     

MS-Xα calculations on boron trihalides and comparison with their photoelectron spectra

The multiple-scattering Xα model has been applied to the sequence of boron trihalides BX₃ where X = F.C1. Br, and I. Transition state calculations show good agreement with the experimental ionization potentials measured by photoelectron spectra.     

Photoelectron spectra of molecules. II. Carboxylic acids and their esters

He I photoelectron (PE) spectra of four carboxylic acids and five esters are measured. Semiempirical and ab initio quantum chemical calculations are used for the interpretation of the spectra. The complex approach which uses empirically established relationships (the dependence of valence electron ionization energies on proton affinities in the gas phase, on the core level ionization energies, and on the structure) was developed. © 1997 John Wiley & Sons, Inc.     

Fine-structure vibronic fluorescence spectra of meso-substituted porphyrins and their interpretation

Fine-structure fluorescence spectra have been recorded on selective laser excitation at 4.2 K for meso-tetraethylporphyrin (TEP), meso-tetrapropyl-porphyrin (TPP) and their derivatives with deuteriated NH groups. An interpretation of the spectra obtained is proposed on the basis of calculations of the normal vibrations of the molecules. It was noted that the interaction of the ethyl groups of TEP with the solvent leads to different orientations of these groups to the plane of the macrocycle, which leads to an increase in the number of lines in the frequency range 150–400 cm^–1 and to their broadening.Translated from Teoreticheskie i Éksperimental'naya Khimiya, Vol. 26, No. 6, pp. 664–668, November–December, 1990.     

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.     

Vibrational spectra of pyrazole in various aggregate states and their interpretation

The selection of the fundamental frequencies of pyrazole and the assignment of them to various types of vibrations were made on the basis of a comparison of the IR and Raman spectra of pyrazole and some of its isotopically substituted derivatives in various aggregate states and in the form of complexes with CdCl₂. The assignment was confirmed by prior calculation of the frequencies and forms of the vibrations of pyrazole.     

Structures,raman, infrared and electronic absorption spectra of pyridinium trihalides

Vibrational and electronic absorption spectra of PyHI₃, PyHIBr₂, PyHICl₂, PyHBr₃ and PyHBrCl₂ are presented and explained in terms of the vibrations and electronic transitions, respectively, of the pyridinium and trihalide ions. Two compounds, PyHI₃ and PyHBr₃, show charge transfer bands in the absorption spectra of the solids, and the vibrational spectrum of the PyH⁺ ion in solid PyHBr₃ differs from the normal PyH⁺ spectrum. PyHBr₃ as well as PyHI₃ contains asymmetric trihalide ions in the solid state, as can be concluded from the Raman and infrared spectra.     

Electronic and photoelectron spectra of amino-1-methylnitropyrazoles and their quantum-chemical interpretation

The electronic and photoelectron spectra of isomeric vic-aminonitro-1-methylpyrazoles were interpreted by means of the data from PPP and MNDO quantum-chemical calculations.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1629–1634, December, 1986.     

Photoelectron spectra and electronic structure of aza-boron-dipyridomethene derivatives

The electronic structure of three aza-boron-dipyridomethene derivatives containing different hydrocarbon groups at the boron atom is studied by ultraviolet photoelectron spectroscopy and calculations at the density functional theory level. According to the experimental and theoretical data, the higher occupied molecular orbitals of anthracene, acridine, and the studied complexes are of the same character. For the three studied compounds, the effect of alkyl and phenyl substituents on the electronic structure is determined. The parameters of the electronic structure of aza-boron-dipyridomethene (phenyl groups at the boron atom) and its β-diketonate analogue are compared. It is shown that in an energy range up to 11 eV the calculated results correlate with the ultraviolet photoelectron spectra.     

Photoelectron spectra,electronic and spatial structure of phenylhydrazones

Theoretical and Experimental Chemistry -     

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 spectra and electronic structure of derivatives of imidazoline

We have obtained for the first time the photoelectron spectra (PES) of 20 diamagnetic and paramagnetic derivatives of imidazole. On the basis of calculations in the MNDO approximation, analysis of the vibrational structure, and comparisons in a series we have interpreted the bands in the range 7–11 eV. In the nitroxyl radicals of 3-imidazoline the highest occupied molecular orbital is the _NO ^* orbital, having also a contribution on the C⁴ atom. On introducing N-oxide groups there is a considerable rearrangement of the electronic structure of the radicals. In the PES of the nitroxyl radicals of 3-imidazoline-3-oxide there is multiplet splitting of the ionization band of the n_o·MO, amounting to 0.3–0.4 eV. Replacement of the methyl groups on the C² atom by methoxyl groups leads to an increase in the interactions of the unshared pairs of the O atoms of the nitronium and nitroxyl groups, while the same replacement on the C⁵ atoms leads to a considerable decrease in this interaction. When the substituent on the N¹ atom in derivatives of 3-imidazoline-3-oxide is varied the energy of ionization of the _C-NO MO decreases in the series: CH₃ < H OH < O < NO.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1769–1777, August, 1990.     

Photoelectron spectra and electronic structures of some chlorosulfonyl pseudohalides

The electronic structures of chlorosulfonyl pseudohalide ClSO2X (X = Cl, NCO, N3) are studied by photoelectron spectroscopy (PES) combined with the OVGF calculation at 6-311++G(3df) basis sets. The first ionization potentials for ClSO2NCO and ClSO2N3 are determined to be 12.02 and 11.43 eV, respectively, for the first time, and their features in the PE spectra were assigned based on comparison with related compounds and with high level quantum calculations. Photoelectron spectra of ClSO2NCO and ClSO2N3 suggest that the interactions between chlorine "lone-pair" electrons and two pseudohalogen groups have significant effect on the HOMOs of two compounds, besides the influence of their electronegativity on the first ionization energies.     

Photoelectron spectra of powder and single crystalline chromium-copper disulfides

2p _3/2,1/2 Photoelectron spectra of single crystalline specimens of chromium-copper disulfides CuCrS₂ and CuCr_0.85V_0.15S₂ are studied. It is shown that the spectra of single crystalline specimens substantially differ from the corresponding spectra of chromium-copper disulfides in the powder state.     

Photoelectron spectra of 1,2,3-triazine and its methyl derivatives

The He(1α) photoeletron (PE) spectra of 1,2,3-triazabenzene and its five mono-, di-, and tri-methyl derivatives are repored. The PE bands are assigned by comparison with the results of molecular orbital (MO) calculations and empirical correlation procedures.