Relativistic Jahn-Teller effects in the photoelectron spectra of tetrahedral P4, As4, Sb4, and Bi4

The group-V tetrahedral cluster cations P(4)(+), As(4)(+), Sb(4)(+), and Bi(4)(+) are known to exhibit exceptionally strong Jahn-Teller (JT) effects of electrostatic origin in their (2)E ground states and (2)T(2) excited states. It has been predicted that there exist, in addition, JT couplings of relativistic origin (arising from the spin-orbit (SO) operator) in (2)E and (2)T(2) states of tetrahedral systems, which should become relevant for the heavier elements. In the present work, the JT and SO couplings in the group-V tetramer cations have been analyzed with ab initio relativistic electronic structure calculations. The vibronic line spectra and the band shapes of the photoelectron spectra were simulated with time-dependent quantum wave-packet methods. The results provide insight into the interplay of electrostatic and relativistic JT couplings and SO splittings in the complex photoelectron spectra of these systems.     

Comparison of the crystal structures of sodium orthosilicate,Na4SiO4, and sodium orthogermanate,Na4GeO4

The crystal structures of Na₄SiO₄ and Na₄GeO₄ are isotypic, despite a difference in coordination numbers: in Na₄SiO₄ only one of the four symmetrically independent sodium atoms is four coordinated, in Na₄GeO₄ two of them are.

---

Vergleich der Kristallstrukturen von Natriumorthosilikat, Na₄SiO₄, und Natriumorthogermanat, Na₄GeO₄ (Kurze Mitteilung)

Zusammenfassung Die Kristallstrukturen von Na₄SiO₄ und Na₄GeO₄ sind isotyp, trotz eines Unterschiedes in den Koordinationszahlen: im Na₄SiO₄ ist nur eines der symmetrisch unabhängigen Natriumatome vierfach koordiniert, während es im Na₄GeO₄ derer zwei sind.

     

The electronic structure of FeO 4 2− , RuO4, RuO 4 − , RuO 4 2− and OsO4 by the HFS-DVM method

The electronic structures of FeO ₄ ^2? , RuO₄, RuO ₄ ^? , RuO ₄ ^2? and OsO₄ have been investigated using the Hartree-Fock-Slater Discrete Variational Method. The calculated ordering of the valence orbitals is 2t ₂, 1e, 2a ₁, 3t ₂ andt ₁ with thet ₁ orbital as the highest occupied. The first five charge transfer bands are assigned as:t ₁→2e(v ₁), 3t ₂→2e(v ₂),t ₁→4t ₂(v ₃), 3t ₂→4t ₂(v ₄) and 2a ₁→4t ₂(v ₅). It is suggested that ad-d transition should be observed at 1.5 eV in RuO ₄ ^? and RuO ₄ ^2? .     

The properties and some reactions of 4-oxo-1, 5-diazabicyclo[4, 4, 0]decane and 5-oxo-1, 4-diazabicyclo[4, 4, 0]decane

The chemical properties of 1,4- and 1,5-diazabicyclo[4, 4, 0]decanes and their 5- and 4-oxo derivatives, respectively, have been studied.     

ChemInform Abstract: Ab initio Study on the Be2F4, Mg2F4 Dimers,on the Mixed Dimers BeMgF4 and LiNaF2 and on the Li2BeF4, LiBCl4 and LiAlCl4 Ion-Pairs

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

X-ray emission and X-ray photoelectron studies of the electronic structure of the polymeric cubane cluster compounds Mo4S4Cl4, GaMo4S8, and GaMo4S4Te4

X-ray emission and X-ray photoelectron spectroscopy was used to study the electronic structures of the polymeric cubane cluster compounds Mo₄S₄Cl₄, GaMo₄S₈, and GaMo₄S₄Te₄. It is revealed that the ligand orbitals make significant contributions to the highest occupied molecular orbitals (M−M bonds). Substitution in the series Cl−S−Te increases the covalence of the metal—bridging ligand bonds. The experimental spectra allowed the construction of a qualitative scheme of the electronic structure of Mo₄S₄Cl₄. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 6, pp. 1038–1045, November–December, 1995. Translated by I. Izvekova     

Experimental and theoretical determination of the dipole-quadrupole and dipole-octopole polarizabilities of the group IV tetrachlorides TiCl4, ZrCl4, and HfCl4

The dipole-quadrupole and dipole-octopole polarizabilities A and E of TiCl4, ZrCl4, and HfCl4 have been determined from collision-induced light-scattering experiments. Our respective experimental results for /A/ are (165+/-10), (110+/-30), and (140+/-20) e2a0 3Eh (-1), whereas /E/ is determined to be (675+/-125), (750+/-200), and (670+/-400) e2a0 4Eh (-1). Theory predicts values convincingly close to experiment, as A=(181.4+/-9.1), (167.6+/-8.4), and (139.8+/-7.0) e2a0 3Eh (-1), and E=(-671+/-67), (-688+/-69), and (-574+/-57) e2a0 4Eh (-1). In addition our quantum chemical ab initio calculations give reliable values for the dipole polarizability alpha, as well as for the octopole and hexadecapole moments Omega and Phi for all three substances.     

Synthesis,crystal structure,and magnetic properties of the oxometallates KBaMnO4 and KBaAsO4

Single crystals of KBaMnO₄ and KBaAsO₄ were grown using the hydroflux method and characterized by single crystal X-ray diffraction. Both compounds crystallize in the orthorhombic space group Pnma with a = 7.7795(4) Å, b = 5.8263(3) Å, and c = 10.2851(5) Å for the manganate and a = 7.7773(10) Å, b = 5.8891(8) Å, and c = 10.3104(13) Å for the arsenate. The materials exhibit a three-dimensional crystal structure consisting of isolated MnO₄³⁻ or AsO₄³⁻ tetrahedra, with the charge balance maintained by K⁺ and Ba²⁺. Each tetrahedron is surrounded by six K⁺ and five Ba²⁺, and shares its corner/edge with KO₁₀ polyhedra and corner/edge/face with BaO₉ polyhedra, respectively. The crystal growth, crystal structure and magnetic properties are discussed.     

Activity and Osmotic Coefficients from the Emf of Liquid-Membrane Cells. VII: Co(ClO4)2, Ni(ClO4)2, K2SO4, CdSO4, CoSO4, and NiSO4

The activity coefficients of CdSO₄ CoSO₄, and NiSO₄ are determined from the emf of liquid-membrane cells, like those described in the papers I–VI of this series. The activity coefficients of the auxiliary salts Co(ClO₄)₂, Ni(ClO₄)₂, and K₂SO₄, needed to eliminate the problem of extrapolation to infinite dilution of the 2–2 salts, are also measured. CdSO₄ CoSO₄ and NiSO₄ in the dilute region deviate downward from the limiting law by a larger extent than believed in the past, thus creating the need for the activity coefficients to be recalculated and systematically lowered by 8–16%. The activity coefficients of Co(ClO₄)₂ and Ni(ClO₄)₂, too, need to be corrected by around –3%. For K₂SO₄, the original values, although scattered, were substantially correct. Pitzer's theory best-fit parameter, able to provide the activity and osmotic coefficients of the salts considered, are reported.     

Electronic structures of the boron cage molecules B4H4, B4Cl4 and B4F4

Ab initio calculations have been performed on B₄H₄, B₄Cl₄ and B₄F₄ in order to aid our understanding of the bonding in these compounds, which is presumably based on a tetrahedral boron cage. This cage has only 8 electrons and so is less than that expected on the basis of the usual framework electron counting rules. Basis sets with polarisation functions were used at the SCF, CI and CPF levels of theory to confirm that the T _d structures are indeed more stable than the D _4h ones. Davidson-Roby population analyses were able to show that many factors, including 3-centre 2-electron bonding and backbonding from the ligand to the boron cage, are of importance in determining the relative stability of the three compounds, of which B₄Cl₄ is the only one that has yet been observed experimentally.     

Theoretical study of the Ar-, Kr-, and Xe-CH4, -CF4 intermolecular potential-energy surfaces

We present a theoretical study of the intermolecular potentials for the Ar, Kr, and Xe-CH4, -CF4 systems. The potential-energy surfaces of these systems have been calculated utilizing second-order M?ller-Plesset perturbation theory and coupled-cluster theory in combination with correlation-consistent basis sets (aug-cc-pvnz; n = d, t, q). The calculations show that the stabilizing interactions between the rare gases and the molecules are slightly larger for CF4 than for CH4. Moreover, the rare-gas-CX4 (X = H, F) potentials are more attractive for Xe than for Kr and Ar. Our highest quality ab initio data (focal-point-CCSD(T) extrapolated to the complete basis set limit) have been used to develop pairwise analytical potentials for rare-gas-hydrocarbon (-fluorocarbon) systems. These potentials can be applied in classical-trajectory studies of rare gases interacting with hydrocarbon surfaces.     

Water activity,osmotic and activity coefficients of aqueous solutions of Li2SO4, Na2SO4, K2SO4, (NH4)2SO4, MgSO4, MnSO4, NiSO4, CuSO4, and ZnSO4 at T=298.15 K

The water activities for aqueous solutions of Li₂SO₄(aq), Na₂SO₄(aq), K₂SO₄(aq), (NH₄)₂SO₄(aq), and sulphates MgSO₄(aq), MnSO₄(aq), NiSO₄(aq), CuSO₄(aq), and ZnSO₄(aq) were determined experimentally at a temperature of 298.15 K with a hygrometric method, at molalities in the range from 0.1 mol·kg⁻¹ to saturation. The osmotic coefficients are calculated from these results. The coefficients of Pitzer’s model was used to fit the osmotic coefficients for each salt solution. These parameters were used to predict solute activity coefficients for the salts studied.     

Synthesis of 4-ethoxycarbonylmethyl-, 4-N-phenylcarbamoylmethyl-, and 4-carboxymethyl-1,3-dithiole-2-thiones and the corresponding 1,3-dithiolium salts

A method for the preparation of 4-ethoxycarbonylmethyl-, 4-N-phenylcarbamoylmethyl-, and 4-carboxymethyl-1,3-dithiole-2-thiones and the corresponding 1,3-dithiolium salts from -bromoacetoacetic ester, -bromoacetoacetanilide, and sodium tertbutyltrithiocarbonate was developed. The compounds were characterized by their IR and PMR spectra.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 180–183, February, 1984.     

Infrared absorption spectra and structure of 1, 1, 4, 4-tetrasubstituted 1, 4-disilacyclohexanes

The IR absorption spectra of 1,1,4,4-tetramethyl- and 1,1,4,4-tetraphenyl-1,4-disilacyclohexanes have been studied. The group spectral analysis of these compounds shows that the silicon atoms have barene properties. The presence at about 980 cm^–1 of one strong band (and not two) of C-C stretching vibrations in agreement with the selection rules confirms the chair form of the heterocycle.     

Cross sections for rotational excitations of CH4, SiH4, GeH4, SnH4 and PbH4 by electron impact

We report differential and integral cross sections for rotational excitation of XH₄ molecules (X: C, Si, Ge, Sn, Pb) from 7.5–30 eV by electron impact. These cross sections were derived from fixed-nuclei scattering amplitudes (Bettega et al. 1995) obtained using the Schwinger Multichannel Method with Pseudopotentials (SMCPP) (Bettega et al. 1993). Our results represent the first rotational excitation cross sections for molecules as large as GeH₄, SnH₄ and PbH₄ using entirely ab initio procedures. The cross sections for CH₄ and SiH₄ obtained with pseudopotentials are in very good agreement with all-electron calculations and with other theoretical results. A comparison between our calculated cross sections and experimental data for CH₄ is in general encouraging, but some discrepancies remain. We found inelastic rotational cross sections and momentum transfer cross sections to be larger for SiH₄, GeH₄, SnH₄ and PbH₄ than for CH₄. We could explain this feature.