A Raman spectroscopic study of the low-frequency vibrations in anisole and anisole-d3

Low-frequency Raman spectra of solid anisole and of solid anisole-d₃ have been recorded at 130 K. The phenyl torsion observed at 148 cm^?1 is shifted to 133 cm^?1 upon deuteration of the methyl group. The twofold torsional barriers calculated from these frequencies are 4033 ± 110 cm^?1 and 4094 ± 123 cm^?1 indicating that coupling to other low-frequency modes in both cases is of the same order of magnitude. The methyl torsional mode was observed at 285 cm^?1 in the spectrum of solid anisole and at 183 cm^?1 in the spectrum of anisole-d₃. The threefold barriers calculated using these frequencies are 1847 ± 20 cm^?1 and 1465 ± 18 cm^?1 respectively. These barrier values indicate that the methyl torsion is coupled to another low-frequency mode. A doublet centered at 230 cm^?1 in anisole is shifted to 245 cm^?1 in anisole-d₃; it is proposed that this is due to a ring mode coupled to the methyl torsion. The splitting is interpreted as an example of Davydov splitting.     

Direct syntheses of Lan+1NinO3n+1 phases (n=1, 2, 3 and ∞) from nanosized co-crystallites

A new direct route for the “bottom up” syntheses of phases in the La_n+1Ni_nO_3n+1 series (n=1, 2, 3 and ∞) has been achieved via single-step heat treatments of nanosized co-crystallized precursors. The co-crystallized precursors were prepared using a continuous hydrothermal flow synthesis system that uses a superheated water flow at ca. 400 °C and 24.1 MPa to produce nanoparticulate slurries. Overall, a significant reduction in time and number of steps for the syntheses of La₃Ni₂O₇ and La₄Ni₃O₁₀ was achieved compared with more conventional synthesis methods, which typically require multiple homogenization and reheating steps over several days.     

The Fermi doublet V2−V3 + V4 of CH3CN as a probe of molecular interactions

The Fermi doublet V₂?V₃ + V₄ of CH₃CN in basic, inert and acidic solvents has been studied by IR and Raman spectroscopy. The values of W, the Fermi coupling coefficient, obtained from IR spectra varies with the nature of the solvent while W evaluated from Raman data remains constant at 12.5 ± 0.5 cm^?1. The similar effects of Bronsted and Lewis acids on the band frequencies and intensities is evidence that the CN group complexes with acids via the N atom “n” electron pair and not the π bond.     

Combined analysis of microwave and infrared spectra of methyl iodide: rotational and l-type doubling constants of the v5, v3+v6 and v2 states

The rotational constant B and the l-type doubling constant q were determined for the v₅, v₃+v₆ and v₂, states of CH₂I from the microwave transition frequencies, in combination with the infrared data previously reported. Since these vibrational states were coupled through the Fermi resonance and the xy-type E-E and A₁-E Coriolis resonances, the analysis was made by setting up and solving the complete form of the secular determinants of the energy matrices. The rotational and l-type doubling constants were determined as B₅, = 0.250 173 cm^?1, B₃₆ = 0.247 600 cm^?1, B₂ = 0.249 369 cm^?1, q₅ = ?0.000 027 cm^?1 and q₃₆ = ?0.000 179 cm^?1, which are unperturbed by Fermi and Coriolis interactions. Other band constants for v₅ and v₃+v₆ were also refined in accordance with the new values of B₅ and B₃₆. The present study indicated that the combined analysis of microwave and infrared spectral data was useful for the precise determination of vibration-rotation, levels in the perturbed system.     

Excess molar enthalpies of {(1 − x2 − x3)Al + x2Bi + x3Ga}(I) alloys

The excess molar enthalpies H_m^E{(1 ? x₂ ? x₃)Al + x₂Bi + x₃Ga}(I) have been measured between 725 and 1170 K along the sections $\text{(1 ? x}{}_2\text{? x}{}_3\text{)}\text{x}{}_3\text{=}\text{1}\text{3}$, 1, and 3, and $\text{x}{}_2\text{x}{}_3\text{=}\text{1}\text{3}$, 1, and 3, with a high-temperature Calvet calorimeter using both the direct- and indirect-drop methods of mixing; experimental uncertainty is quoted respectively at 6.7 per cent and 9.9 per cent. The equilibrium temperatures confirmed phase boundaries previously determined by potentiometry, d.t.a., and calculation. Extrapolation of the experimental excess molar enthalpies to the limiting binary alloys {(1 ? x₂)Al + x₂Bi} allows new values for the excess molar enthalpies of these alloys to be proposed. The excess molar enthalpies of the ternary liquid mixtures can be represented correctly using these new values and Bonnier's equation.     

Electrical Behavior of New Orthophosphates Na2M3(PO4)3 (M3=GaMn2, GaCd2, InMn2 and FeMnCd) with Alluaudite-Like Structure

New sodium orthophosphates of general formula Na₂M₃(PO₄)₃ belonging to the alluaudite-type structure have been synthesized and characterized by neutron and X-ray powder diffraction. The nature of the M₃ elements (M₃=GaMn₂, GaCd₂, InMn₂ and FeMnCd) was chosen in order to analyze their influence on electrical and magnetic properties. The conductivity of these materials was measured by the complex impedance method and the transport mechanism was studied from complex permittivities and modulus formalism. Electrical results including charge/discharge experiments showed two main behaviors: GaCd₂ and FeMnCd behave as purely ionic conductors whereas GaMn₂ and InMn₂ are mixed ionic-electronic conductors. The magnetic susceptibility data reveal the antiferromagnetic behavior of FeMnCd, InMn₂ and GaMn₂, with a weak ferromagnetic transition at low temperatures.     

Experimental and theoretical study of the IR spectrum of [(CH2OH)3CNH3]2SiF6 crystal

[(CH₂OH)₃CNH₃]₂SiF₆, (tris(hydroxymethyl)aminomethane)₂SiF₆ crystal, abbreviated as (TRIS)₂SiF₆ crystal, exhibits a solid-solid phase transition (PT) at 182 K. The phase transition is connected with reorientational motion of SiF₆²⁻ and -CH₂OH groups. The vibrational infrared spectra of powdered (TRIS)₂SiF₆ crystal in Nujol and Fluorolube mulls were studied in the wide range of temperatures, from 320 K to 133 K. A wide region of internal vibrations of the TRIS⁺ and SiF₆²⁻ ions was investigated. Temperature changes of wavenumber, width, centre of gravity, and intensity of bands were analyzed to clarify the molecular mechanism of the phase transitions. Theoretical calculations were made based on density functional theory (DFT). The calculated normal vibrational modes of the molecules, their frequencies and intensities were compared with those obtained from experimental data.     

Pulsed NMR of cis-polyisoprene solutions T1 and T2 relaxations,free volume,viscosity relationships

Previous pulsed NMR studies of polyisoprene have largely been concerned with entangled or crosslinked networks. This paper deals with (i) the relaxation of high molecular weight entangled; (ii) cross-linked; (iii) monodisperse low molecular weight; and (iv) high molecular weight polymer in the presence of tetrachloroethylene which, by increasing molecular mobility, can be expected to influence the NMR relaxation. For all four types of polyisoprene, the spin-lattice T₁, relaxation shows a minimum with position depending only on the free volume, as influenced by changes in temperature T and polymer concentration v₁,. For monodisperse polyisoprene of molecular weight 7200, insufficient to form an entangled network, the spin-spin relaxation decay constant T_2L is quantitatively related to the free volume ₁ by two parameters A′ and B″ when the free volume is altered by a change in temperature, or in polymer concentration (10–100/). This can also be expressed in the form where the parameter T_∞ at 100% concentration agrees with the value used to describe rheological properties. At other concentrations of polymer, T_∞ and B′ can be derived quantitatively from the coefficients of volume expansion of polymer and solvent. The variation of T_2L with molecular weight (T_2L ∝ M^?0.5) occurs via the A′ parameter. It is concluded that T_2L can be quantitatively related to the free volume available for molecular motion (as influenced by temperature and solvent concentration) as well as to molecular weight. Furthermore T_2L is simply related to viscosity n, over a wide range of temperatures and concentrations. T₂ can be used to analyse the molecular motions involved in theology.     

Variational principles for E3

New variational principles are given for E₃ in RS perturbation theory, also a unified derivation of several other principles. An example with a unknown π₀ is treated.     

A CNDO/S study on the Tn ← T1 absorption spectrum of 1,1′-binaphthyl

CNDO/S calculations demonstrate that changes in the T_n ← T₁ absorption spectrum of 1,1′-binaphthyl in going from rigid to fluid media is consistent with a rotation of the chromophores about the interconnecting bond to a nearly planar trans configuration.     

Crystal structure and luminescence of compounds A3BC10O20

In this paper we describe compounds A₃BC₁₀O₂₀ (A = Sr, Ba, Pb; B = Ti, Ge, Sn; and C = Al, Ga). The crystal structure of Ba₃TiAl₁₀O₂₀ has been determined by neutron powder profile refinement. The luminescence of these compounds has been investigated. Apart from the titanate luminescence of Ba₃TiAl₁₀O₂₀, these compounds show a semiconductor type of luminescence.     

Crystal structure of Ln1/3NbO3 (Ln=Nd, Pr) and phase transition in Nd1/3NbO3

The crystal structure of the A-site deficient perovskite Ln_1/3NbO₃ (Ln=Nd, Pr) at room temperature has been determined, for the first time, as orthorhombic in space group Cmmm using high-resolution neutron powder diffraction. Pertinent features are the alternation of unoccupied layers of A-sites and layers partly occupied by Ln cations, as well as out-of-phase tilting of the NbO₆ octahedra around an axis perpendicular to the direction of the cation/vacancy ordering. The phase transition behaviour of Nd_1/3NbO₃ has also been studied in situ. This compound undergoes a continuous phase transition at around 650 °C to a tetragonal structure in space group P4/mmm due to the disappearance of the octahedral tilting. The analysis of spontaneous strains shows that this phase transition is tricritical in nature.     

Direct IR spectroscopic study of the cyclopentadienyl radical

The products of vacuum pyrolysis of bis(cyclopentadienyl)nickel have been studied by matrix isolation infrared spetroscopy. Three IR bands at 3079, 1383 and 661 cm^–1 corresponding to the cyclopentadienyl radical have been observed. A comparison of the IR spectrum of the radical C₅H₅ with those of the ligand -C₅H₅ and free anion^–C₅H₅ has been performed.These results were presented for the first time in O. M. Nefedov's plenary lecture at X IUPAC Conference on Physical Organic Chemistry (Haifa, Israel, August 1990) (see ref. 1 and literature cited therein).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1497–1499, August, 1993.     

Ch-stretching gas phase overtone spectrum of symmetric neopentane-d4

The overtone spectrum of neopentane-d₄, C(CH₂D)₄, is examined and the local mode model is used to assign the prominent peaks. Proposed coupling routes for intramolecular vibrational relaxation of CH-stretching overtones are discussed. The dominant vibrational relaxation pathway is identified by comparisons of neopentane-d₄, neopentane and benzene overtone bandwidths.     

Electric dipole moment of Ph3 in the v4 = 1 state

The electric dipole moment of PH₃ in the v₄ = 1 state was measured by means of the Stark effect on the first two l-type doubling transitions     

Direct observation of the ν6 band in the IR spectrum of CF3I dissolved in liquid xenon

The IR spectrum of CF₃I dissolved in liquefied xenon at 185 K shows a very weak peak at 265.2 cm^?1 due to the ν₆ fundamental vibration. The separation, $\text{ν}$₃  $\text{ν}$₆, 19.3 cm^?1 is the same as that deduced from the microwave spectrum of CF₃I in the gas phase.     

NQR study of ternary chalcogenides A3BX3, ABX2, and ABX where A = Cu,Ag, or TI, B = As or Sb,and X = S or Se

¹²¹Sb, ¹²³Sb, ⁷⁵As, ⁶³Cu, and ⁶⁵Cu NQR resonances are reported for CuSbSe₂, Tl₃SbSe₃, Tl₃SbS₃, Tl₃AsS₃, Tl₃AsSe₃, Ag₃AsSe₃, TlSbS₂, CuAsS, AgAsS, and Cu₅SbS₃I₂. Tl₃SbSe₃ is an incongruently melting compound not observed in an earlier phase-diagram study of the pseudobinary system Tl₂SeSb₂Se₃. For isostructural arsenic and antimony chalcogenides the ratio of ⁷⁵As to ¹²¹Sb quadrupole coupling constants is 0.42, and for the BX₃ group in binary or ternary corresponding pairs of sulfide and selenides the ratio of quadrupole coupling constants for ⁷⁵As or ¹²¹Sb is 0.83. A reversible phase transition was observed at 130 K for Ag₃AsSe₃. Unit cell parameters are reported for crystals of TlSbS₂ and Cu₅SbS₃I₂.     

On AgRhO2, and the new quaternary delafossites AgLi1/3M2/3O2, syntheses and analyses of real structures

Two new quaternary delafossite type oxides with the general formula Ag(Li_1/3M_2/3)O₂, M=Rh, Ir, have been synthesized, and their structures characterized. Based on X-ray and electron diffraction analyses the structural similarity with AgRhO₂ delafossite, has been evidenced. The real structures of the quaternary delafossites have been revealed, which has allowed to fully explain the diffuse scattering as observed in X-ray powder diffraction. AgRhO₂ is thermally stable up to 1173 K, the behavior of the two quaternary compounds AgLi_1/3Rh_2/3O₂ and AgLi_1/3Ir_2/3O₂ is comparable, and they decompose above 950 and 800 K, respectively. AgRhO₂ shows temperature independent paramagnetism, while for the other two an effective magnetic moment of 1.77μ_B for Ir, and 1.70μ_B for Rh were determined, applying the Curie-Weiss law. All compounds are semiconducting with activation energies of 4.97 kJ mol⁻¹ (AgLi_1/3Rh_2/3O₂), 11.42 kJ mol⁻¹ (AgLi_1/3Ir_2/3O₂) and 17.58 kJ mol⁻¹ (AgRhO₂).