F. G. Herring

Photoelectron Spectra of F2O and Cl2O

The valence ionization potentials of F2O and Cl2O have been determined by photoelectron spectrometry, and the results are compared with the predictions of ab initio and approximate LCAO SCF calculations. The first PES band shows vibrational structure which is assigned to ν1 for F2O, and to both ν1 and ν2 for (Cl2O). These frequencies all show slight increases over the corresponding values for the ground states of the neutral molecules.

The ionization potentials of ammonia and ammonia-d3. Measured by photoelectron spectroscopy, and an indo calculation of these values

Abstract New high resolution photoelectron spectra of ammonia and ammonia- d 3 are reported. The spectra of both compounds show two ionization processes corresponding to ionization from the 3a and 1e molecular orbitals. The first band in the photoelectron spectrum of each compound shows a well-resolved vibrational progression which is assigned to v 2 , the totally symmetric out-of-plane bending mode. Calculations of the ionization potentials have been carried out using the CNDO/2 and INDO molecular orbital methods. The INDO method gave better results than the CNDO/2 calculation but both sets of values were higher than the experimental ones.

The ionization potentials of methyl cyanide and methyl acetylene by photoelectron spectroscopy and semi-rigorous LCAOSCF calculations

Abstract The photoelectron spectra of methyl cyanide, methyl cyanide-d3, and methyl acetylene have been measured using the 584A helium resonance line as a light source. On the basis of CNDO/2 and INDO calculations the ionization potentials determined are assigned to ionizing processes from the various orbitals in molecules.

Ionization Potentials of the Difluoroamino Radical by Photoelectron Spectroscopy and INDO Calculations

The photoelectron spectrum of the NF2 radical has been measured. The spectrum shows evidence for three vertical ionization potentials at 12.10, 14.60, and 16.38 eV. The adiabatic first ionization potential was found to be 11.62 eV. LCAO–INDO calculations have been employed to deduce the excitation energies of the NF2+ ion, and these are compared with the experimental values. The calculations indicate that the 1A1 state of the bent NF2+ ion is lower in energy than the linear 3Σ− state. Vibrational structure is clearly seen on the first band (1250 cm−1) and on the second (520 cm−1), and there is evidence that both progressions belong to the symmetric stretching mode ν1(a1).

The ionization potentials of borazine by photoelectron spectrometry and indo theory

Abstract The 584 A photoelectron spectrum of borazine is given, and the ionization potentials compared with previously calculated values and with those found by an INDO calculation.

The fluidity of plasma membranes of Dictyostelium discoideum. The effects of polyunsaturated fatty acid incorporation assessed by fluorescence depolarization and electron paramagnetic resonance.

Two probe techniques, fluorescence depolarization (using diphenylhexatriene) and electron paramagnetic resonance (using 5-doxyl stearic acid), have been used to assess the fluidity of the purified plasma membranes of Dictyostelium discoideum. Both techniques indicate that a large incorporation of polyunsaturated fatty acids into the plasma membranes does not significantly change membrane fluidity In addition, phosphatidylcholines isolated from cells grown on both polyunsaturated fatty acid-supplemented and unsupplemented media exhibit similar mobilities of an incorporated spin probe when dispersed in aqueous solution. This result suggests that the enrichment of a membrane already high in content of fatty acyl chains containing two double bonds with those containing three or more double bonds does not markedly change fluidity.

Fixation of amine copper preservatives. Part 1. Reaction of vanillin, a lignin model compound with monoethanolamine copper sulphate solution

Summary The fixation reaction of copper-ethanolamine preservatives in wood was studied using the reaction between vanillin, a lignin model compound, and ethanolamine-copper sulphate solution. The green compound precipitated after the reaction has been characterized spectroscopically as di(ethanolamine)-bis (vanillinato)dicopper(II); [Cu(vanillin) (ethanolamine)]2. Single crystal X-ray crystallographic studies showed that the crystals of [Cu(vanillin)(ethanolamine)]2 are triclinic with the space group P1 with a = 9.1271(7), b = 10.8723(9), c = 6.360(1) Å, α = 97.08(1), β = 100.63(1), and γ = 110.024(7)°. Z = 1. The binuclear molecule has crystallographic inversion symmetry. The ligand arrangement around the Cu(II) is a distorted square based pyramid, with a base plane made up of two oxygen atoms from the ethanolamine ligands, one oxygen atom from a hydroxyl group in vanillin and one nitrogen atom from ethanolamine. Two Cu-O [1.916(2) and 1.950(5) Å], one Cu-O (hydroxyl) [1.926(4) Å] and one Cu-N [1.999(3) Å] bonds form a plane with Cu-O (methoxyl) [2.303(2) Å] bond in an axial direction at an angle 77 ° to the plane. The result suggests that after treatment with copper-ethanolamine wood preservatives, stable copper-nitrogen-lignin complexes can be formed through reaction with guaiacyl units in lignin.

Fixation of Ammoniacal Copper Preservatives: Reaction of Vanillin, a Lignin Model Compound with Ammoniacal Copper Sulphate Solution

A model for the fixation of ammoniacal copper preservatives in wood was examined through reaction of vanillin, a lignin model compound, with ammoniacal copper sulphate solution. The compound produced on evaporation of the aqueous ammoniacal solution has been characterized spectroscopically as di(amine)bis(vanillinato)copper(II) ; [Cu(vanillin) 2 (NH 3 ) 2 ]. Single crystal X-ray crystallographic studies showed that the crystals of [Cu(vanillin) 2 (NH 3 ) 2 ] are monoclinic with space group P21 with a = 5.4172(9), b = 15.452(2), c = 10.4595(9)A, Z = 2. The ligand arrangement around the Cu(II) is a distorted octahedron. Two Cu-N [2.014(5) and 2.034(5) A] and two Cu-O (hydroxyl) [1.969(4) and 1.972(4) A] bonds form a plane with Cu-O (methoxyl) [2.371(3) and 2.388(3) A] bonds in an axial direction at an angle 75° to the plane. The copper-nitrogen bonding is trans oriented in the plane. Electron spin resonance (ESR) was used to determine the g-tensor and hyperfine tensor elements from both a polycrystalline sample and a DMSO solution. The result suggests that ammoniacal copper wood preservatives can form stable copper-nitrogen-lignin complexes through reaction with guaiacyl units in lignin.

The photoelectron spectrum of the free radical chlorine dioxide

Abstract The photoelectron spectrum of the free radical ClO2 shows seven ionization potentials, with vertical values of 10.48, 12.94, 15.45, 17.50, 17.95, 19.36 and 20.89 eV. To aid in interpreting the experimental ionization potentials CNDO/2 calculations were carried out assuming that the ion had the same geometry as the parent free radical. These calculations showed that the electron configuration for ClO2 is …a22b22a12b11 and for ClO2+ is …a12b22a22 with the lowest unoccupied being b1. The vibrational structure evident on the first band (980 cm−1) is assigned to the ν1 mode, and is 4% higher in frequency than the corresponding value of ν1 in the neutral molecule, which reflects the antibonding nature of the (b1) orbital.

Electron Spin Resonance Spectrum of the Chlorodisulfanyl (S2Cl) Radical in Inert Matrices at 4.2°K

A new species, the chlorodisulfanyl radical (ClSS), has been produced by photolysis of dichlorodisulfane (Cl2S2) in inert matrices at 4.2°K. The identification of ClSS rests on the complete simulation of its well resolved electron spin resonance spectrum. A versatile computer program was developed for this purpose. The method of computation is perfectly general and takes into account the noncoincidence of the principal axes frames of the various tensors in the spin Hamiltonian which, apart from the usual g and A tensors, includes a quadrupole coupling tensor and nuclear Zeeman term. The chlorodisulfanyl radical possesses anisotropic g and hyperfine tensors which have principal axes rotated relative to each other by 10° in the molecular plane. In addition to this, the fact that the chlorodisulfanyl radical has been found to have a quadrupole coupling tensor which is of comparable magnitude to the hyperfine interaction tensor leads to a rather complicated ESR spectrum for the randomly oriented species. Our ...