ESCA studies of some copper and silver selenides

Photoelectron and Auger spectra have been obtained for the copper and silver selenides CuSe, Cu ₂Se, Ag ₂Se, and AgCuSe as well as from CuS, Ag ₂O, Ag ₂S, Cu, and Ag. Binding-energy values, chemical shifts, and peak-shapes are reported for the Cu 3 d, Ag 4 d and Se 3 p electrons. Absence of multiplet splitting and shake-up structure is discussed in relation to the magnetic properties. It is shown that chemical shifts are much better revealed in the Auger spectra (Cu L₃M_4,5M_{4, 5} and Ag M₅N_{4, 5}N_{4, 5}) than in the direct photoelectron ones. In addition the use of the Auger parameter to characterize the series under study is emphasized. Finally the valence-band spectra have been examined and the electronic structures are interpreted.     

An E.S.R. study of some alkyl substituted benzene anion radicals : an experimental evaluation of the extent of vibronic interaction

E.S.R. studies of the proton hyperfine splitting in the anion radicals of benzene, toluene, ethylbenzene, iso-propylbenzene, t-butylbenzene, and p-xylene show that it is strongly dependent upon temperature. In the case of the monoalkylbenzenides there are two contributions to this observed temperature dependence. First, there is a rapid thermal averaging over two near-degenerate states which have different spin-density distributions. The energy separations between these two near-degenerate states have been measured for the above series of monoalkylbenzenides and are reported here. It is also possible to measure experimentally the spin-density distributions for the two states between which the averaging takes place. With this information one can obtain an experimental estimate of the extent of vibronic interaction which occurs in these systems. Such estimates are presented here and compared with those obtained theoretically. The second source of the strong temperature dependence of the proton hfs lies in the temperature dependence of the sigma-pi interaction parameter, Q _H. The sigma-pi interaction parameter has been studied as a function of temperature for all members of the above series and the results reported. Finally, restricted rotation of the iso-propyl group in the anion radical of iso-propylbenzenide was observed and the barrier to rotation has been measured.     

Photoelectron-spectroscopic study of nickel,manganese and cobalt selenides

Photoelectron-spectroscopic studies (XPS and UPS) have been carried out to investigate electronic structure and chemical bonding in the monoselenides of nickel, manganese and cobalt. Binding-energy values and chemical shifts are reported from the XPS measurements for Ni 2p and 3s, Mn 2p and 3s, Co 2p and 3s and Se 3p and 3d. The electronic structure and bonding in the monoselenides are interpreted from an analysis of the valence-band spectra. The combined XPS and UPS data suggest transfer of electrons from the metal orbitals (Ni, Mn and Co) to selenium, contrary to bonding schemes proposed previously in the literature. Magnetic-susceptibility measurements performed by us indicate NiSe to be diamagnetic and MnSe and CoSe to be highly paramagnetic at room temperature. The presence of shake-up satellites in the XPS spectra for MnSe and CoSe and their absence for NiSe are discussed in relation to these magnetic properties.     

A photoelectron spectroscopic study of benzonitrile,ethynylbenzene and some of its substituted derivatives

The He-I photoelectron-spectra of ethynylbenzene and benzonitrile have been reinvestigated. An assignment is given to the low lying ionization potentials as well as of those ranging up to 21 eV, which were not accounted for in previous work³. Furthermore, the He-I photoelectron-spectra of some ω- and para-substituted ethynylbenzenes are discussed. A close inspection of the vibrational structure associated to the third ionization potential of ethynylbenzene and its ω-deutero-derivative clearly shows the quasi-π-orbital to be highly localized on the acetylenic triple bond.     

Combination of microwave reactions with fluorous separations in the palladium-catalyzed synthesis of aryl sulfides

Coupling of microwave reactions with fluorous separations can dramatically increase the efficiency of high-speed synthesis. Described in this paper is a fluorous synthesis of aryl sulfides by palladium-catalyzed cross-coupling of aryl perfluoroalkylsulfonates (C8F17O2SOAr) with thiols (RSH) under microwave irradiation. Fluorous solid-phase extractions (F-SPE) are employed for the purification of reaction mixtures. No fluorous solvents are involved in reaction and separation processes. The fluorous synthesis is further extended to the multi-step synthesis of substituted hydantoin and amide scaffolds.     

Mass spectral condition for leptons and quarks

Consideration is given to the mass spectral conditiona(a,_m)a =a _m, wherea is the annihilation operator forQ=–1 states in the Hilbert space of leptons and quarks anda _m is the commutator resolvent ofa with respect tom. It is observed that this spectral condition, which simply requires a to be a congruent automorph ofa _m , implies that the third-, fourth-, and fifth-generationQ=-1 leptons have the masses 1788.03 MeV, 42.1649 GeV, and 1.33422 TeV, respectively. With the assumption that the mass spectral condition also holds forQ=0 states in the Hilbert space, one obtains new theoretical upper and lower bounds on the neutrino masses.     

Splitting of the Cr 2p ions states in some ternary sulphides and selenides

X-ray photoelectron spectroscopy was used to investigate ACr₂S₄ (, Zn, Mn, Fe, Fe:Cu) and BCr₂Se₄ (, Cu, Hg, Hg:Cu) single crystals. Well defined splitting of the Cr 2p core level has been found. The local magnetic moments of the Cr ions are responsible for the observed effect. Received 2 November 1999     

ENDOR studies of alkyl substituted p-Benzosemiquinones in reversed micelles and in 2-propanol

Various substituted p-benzosemiquinone radical anions, inter alia ubisemiquinone and derivatives, have been investigated in 2-propanol and in reversed micelles by EPR and ENDOR spectroscopy. Unsymmetrical semiquinones, with respect to the oxygen atoms, experience remarkable hyperfine shifts depending on the medium. This effect even allows differentiation between stereoisomers. Immobilization of the semiquinone molecules at the water-surfactant interface in reversed micelles gives rise to pronounced asymmetric linewidth effects. In the case of 2-cyclohexyl-3-methyl-1,4-benzosemiquinones, mixtures of two species (conformers) have been observed.     

Calculation of some characteristics of substituted benzenes

Compounds of the C₆H₅XY₁Y₂ type have been examined, and the dependence of energy and wave functions ona _Y, ß_XY and ß_CX has been studied. Numerical calculations have been carried out and tables compiled.In conclusion the authors would like to thank N. A. Prilezhaev and V. I. Danilov, who helped us daily in carrying out this work.     

Conductometric study of complex formations between some substituted pyrimidines and some metal ions in acetonitrile and the determination of thermodynamic parameters

The complexation reactions between Cr³⁺, Cd²⁺, Co²⁺, Ni²⁺, Hg²⁺, Zn²⁺, Pb²⁺,and Ag⁺ metal ions with diethyl-3-(4-hydroxy-6-methylpyrimidin-2-yl) guanidine (L1), 2-amino,4-hydroxy,6-methylpyrimidine (L2), and 2-(diethylamin),4-hydroxy,6-methylpyrimidine (L3) in acetonitrile (AN) were studied using a conductometric method. The formation constants of the resulting complexes were determined from computer fitting conductance-mole ratio data. The results revealed that the formation constants of L1 with metal ions are varying in order of Cr³⁺ > Pb²⁺ > Zn²⁺ > Co²⁺ > Hg²⁺ > Ag⁺ ~ Cd²⁺ > Ni²⁺. For L2 and L3 the sequence of complex formation constants are follow as Cr³⁺ > Pb²⁺ > Zn²⁺ > Co²⁺ > Cd²⁺ > Hg²⁺ > Ag⁺ > Ni²⁺ and Cr³⁺ > Pb²⁺ > Zn²⁺ > Co²⁺ > Ni²⁺ ~ Hg²⁺ ~ Cd²⁺ ~ Ag⁺, respectively. The values of the thermodynamic parameters (ΔH, ΔS and ΔG) for complexation reactions were obtained from the temperature dependence of the stability constants. In all cases, the complexes were found to be enthalpy stabilized but entropy destabilized. In addition, some ab-initio quantum-mechanical calculations were carried out, in order to obtain a clue about the degree tendency of ligands to metal ions.     

NMR chemical shifts of129Xe dissolved in liquid ethers, secondary amines, and alkyl sulfides

Xenon-129 NMR spectra have been measured for solutions containing Xe dissolved in a variety of linear aliphatic ethers, secondary amines, and alkyl sulfides. The chemical shifts obtained from these data are found to be linearly related to the composition of the solvent molecules expressed as volume fraction of the constituent methyl groups, methylene groups, and the respective oxygen, nitrogen, and sulfur atoms. These results support a model used previously to interpret chemical shifts measured for¹²⁹Xe dissolved in a variety ofn-alkanes and their terminally substituted derivatives. This model treats dispersion force contributions to the chemical shift as resulting from pairwise additive interactions between each dissolved Xe atom and the individual constituent groups of each solvent molecule.     

Photoelectron spectra of some fluorine substituted diazanaphthalenes

The high resolution He 584 Å photoelectron spectra of fluorine substituted 1,2-diaza-, 1,3-diaza-, 1,4-diaza- and 2,3-diaza-naphthalene are presented. By means of fluorine substitution the analysis of the photoelectron spectra of the parent compounds can be made more definite. Unexpected shifts of the nitrogen “lone-pair” bands can be explained within the through-space and through-bond interaction model. From this explanation one can deduce that fluorine substitution can give experimental evidence about the symmetry character of the “lone-pair” molecular orbitals.     

A quantum-chemical study of the spectral and luminescent properties of photoproducts of some 8-azasteroids

The spectral and luminescent properties of photoproducts of two oxy-substituted 8-azasteroids in aprotic and proton-donor solvents are studied with the aid of methods of quantum chemistry. The electronic structure and the absorption and fluorescence spectra of isolated molecules and their complexes with water and proton hydrates are calculated and interpreted. It is shown that, orbitally, the first excited singlet state of photoproducts is close to an analogous ππ* state of 8-azasteroid. The bands observed in the absorption spectra of photoproducts are complex and are formed by two or more transitions. It is found that both neutral and charged complexes of photoproducts with water can fluoresce.     

The laser gain characteristics of some substituted coumarins

A theoretical and experimental study has been made of the small signal gains of six coumarin dyes (DAMC, 4 MU, 7 HC, calcein blue, esculin and scopoletin) in a common solvent (ethanol), and the variation correlated with the different substituents in the coumarins. The relative variation in gain, taking the value for DAMC as the basis, is about 75% for 4 MU, 7 HC and calcein blue, 55% for esculin and 20% for scopoletin. The total tunable range for these dyes is from 430–530 nm. The higher gain in the case of DAMC is attributed to the relatively higher intramolecular charge transfer in this dye compared to the hydroxy-coumarins. The different substituents in the hydroxy-coumarins studied appear to have only a marginal influence on the gain.