William M. Risen

Interionic Vibrations and Glass Transitions in Ionic Oxide Metaphosphate Glasses.

The far infrared spectrum of each ionic metal‐metaphosphate glass, (MPO3)n (M = Li, Na, K, Rb, Cs) and [M(PO3)2]n (M = Ca, Sr, Ba), contains a broad absorption band whose peak frequency, ω0, and halfbandwidth, Δω1/2, are strongly dependent on the mass and charge of the glass‐modifying cation. Each such band, which appears as the envelope of the optical phonon spectrum of the crystalline form of the material, is assigned to a density of coupled oscillator pseudo phonon states, which assignment is shown to be consistent with experimental linear vibrations of ω0 with Δω1/2 and of ω02 with , the integrated absorbance, within the complete set of glasses. The net effect of coupling the oscillators in the vitreous (disordered) system is equivalently treated as a single damped harmonic oscillator. The damping coefficient, b = μΔω1/2, is constant in each series as is the complex part of the refractive index at ω0, κ(ω0), and the Lorentzian band is used to compute the force constant, F, b, and T, 0,...

A laser Raman study of the stress dependence of vibrational frequencies of a monocrystalline polydiacetylene

The applicaiton of a tensile stress to a monocrystalline fiber of a polydiacetylene, an extended‐chain polymer, causes the Raman‐observed C≡C and C=C in‐chain vibrational frequencies to decrease linearly with elongation. The polymer studied, poly‐HDU, results from the solid state polymerization of R–C≡C–C≡C–R, where R=–CH2OCONHC6H5. This experimental relationship between bond frequency shifts and deformation is analyzed by calculating bond force constant changes as a function of macroscopic stress. It is shown that possible effects due to stress‐induced changes in electron delocalization in this fully conjugated polymer are negligible and the principal contributions to the bond frequency shifts are due to bond anharmonicity. Models which assume that the entire effect is due to bond anharmonicity produce calculated dependencies of ν (C=C) and ν (C≡C) upon fractional elongation, which are in good agreement with that observed.

Vibrational spectra of oxygen- and boron-isotopically substituted B2O3 glasses

Abstract The Raman spectra of 10B, 11B, 16O, 18O, and mixed isotopic compositions of B2O3 (gl) are reported. The 808 cm−1 band assigned to the boroxol ring structure is found to shift upon oxygen isotope substitution, and not to depend on the boron mass. It is replaced by four band, in the intensity ratio 1 : 3 : 3 : 1, in the case of the 50% 16O-50% 18O-containing material. On the other hand, the frequencies of other principal bands depend on the masses of both boron and oxygen. The about 1260 cm−1 band, in particular, depends on the masses of both, and shifts without broadening upon partial oxygen substitution. The analysis of these data shows that both a local unit, behaving as predicted for the boroxol ring, and a continuous random network of connecting bonds are manifested in the spectra.

Chitaline materials: soluble chitosan-polyaniline copolymers and their conductive doped forms

Abstract Graft copolymers of polyaniline and chitosan have been synthesized. They are soluble in aqueous solution and form self-supporting materials, including thick films and fibers. Upon protonic doping, their conductivities rise from less than ∼10−7 S/cm to the 10−2 to 10−5 S/cm range, depending on the initial chitosan-to-aniline ratio. Spectroscopic studies show the grafting and demonstrate that the electronic states are similar to those of the emeraldine and protonically doped emeraldine forms of polyaniline.

Raman studies in CuTCNQ: Resonance Raman spectral observations and calculations for TCNQ ion radicals

The Raman spectra of thin film, and powdered crystalline forms of CuTCNQ have been studied and analyzed in connection with their electronic spectra and vibrational normal coordinate analysis and molecular orbital results. Nonresonance and resonance Raman conditions have been obtained by using different sample forms and source wavelengths. Shifts of TCNQ− and TCNQ= vibrational frequencies from those of TCNQ0 due to changes in the charge on the TCNQ moiety have been calculated in terms of molecular orbital parameters and TCNQ0 vibrational frequencies. The resonance Raman enhancement of TCNQ− in the red band system is shown to be of Franck–Condon origin and its resonance Raman spectrum in this region is calculated. Transformation of CuTCNQ to TCNQ0 with different laser lines is explained on the basis of photoinduced electronic transitions.

Rare earth phosphate glasses

Abstract Praseodymium phosphate and dysprosium phosphate glasses with compositions xLn 2 O 3 (1−x)P 2 O 5 have been synthesized and analyzed to be in the x=0.18−0.30 range. Their structures have been studied by infrared, far infrared and laser Raman spectroscopy, and the dependences of the magnetic and thermal properties of the glasses on stoichiometry and structure have been investigated.

Vibrational Spectra of Single and Mixed Alkali Pentasilicate Glasses.

Abstract The far infrared and laser Raman spectra of single and mixed alkali pentasilicate glasses, M 2 O·5SiO 2 (M = Li, Na, Kb, Cs), and x Cs 2 O(1 − x )Na 2 O·5SiO 2 are reported in both the annealed and unannealed forms. Study of the cation-motion bands in the far infrared shows that the vibrationally significant cation-network interactions are unaffected by either introduction of a second cation or by annealing, and these results are discussed in terms of the glass formation and annealing. The spectra of the network show the existence of intrinsic network strain, changes in distributions of bond angles related to alkali mixing and annealing, and evidence for the nature of the distribution of cations in the glass. The results are discussed in relation to the composition dependence of other properties of these and related mixed alkali glasses.

Cation Motion in Anionic Fields of the Polyelectrolytic Salts of Ethylenemethacrylic Copolymers

The far‐infrared spectra of the Li+, Na+, K+, Cs+ salts and acid forms of polyelectrolytic ethylene‐methacrylic acid copolymers have been examined in the 800–33‐cm−1 region at ambient and low temperatures. A broad band, which shifts to lower frequency as the cation mass is increased, is attributed to cation motion in anionic fields, and the appearance of a low frequency band, whose intensity is related to the cation properties, is assigned to perturbed skeletal motions of a neighboring polymer segment. Models are proposed and analyzed for the vibrational modes involving ion motion. The vibrational force constants for aggregate distortion, as calculated from the observed ion‐motion frequencies, are in agreement with such constants computed here employing an ion‐multipole potential energy function which does not use these experimental data. The spectral and theoretical results are considered in terms of the molecular interactions of importance in polyelectrolytes and in the physical properties of these mate...

The PtP(C6H11)3(C2H4)2 mediated activation of aldehyde CH bonds via chelate-assisted oxidative addition reactions

Abstract Hydrocarbon solutions of PtPCy 3 (C 2 H 4 ) 2 (Cy = cyclohexyl) react rapidly with 8-quinolinecarboxaldehyde (1 equiv.) to yield tricyclohexylphosphine quinolinecarboxyl platinum hydride ( 1 ) and CH 2 CH 2 (2 equiv.). Compound 1 reacts with CCl 4 in hydrocarbons to give PtPCy 3 (NC 9 H 6 CO)Cl ( 2 ) and CHCl 3 . The compound PtPCy 3 (C 2 H 4 ) 2 also reacts with Ph 2 P(C 6 H 4 - o -CHO) and Ph 2 As(C 6 H 4 - o -CHO) to give PCy 3 PtPh 2 P(C 6 H 4 - o -CO)(H) ( 3 ) and PCy 3 PtPh 2 As(C 6 H 4 - o -CO)(H) ( 4 ), respectively. Compounds 1, 2, 3, and 4 were characterized by infrared and 1 H NMR spectra, and the crystal structure of 3 was determined by X-ray diffraction. Crystals of 3 are monoclinic, with space group P 2 1 / n and Z = 4 with the unit cell dimensions a 9.7936(17), b 14.844(35), c 23.530(64) A, β 91.817 (18)°, and V 3419.09(1.36) A 3 . The structure is refined to final discrepancy factors of R = 0.055, and R w = 0.064. The molecular structure of 3 is that ligating atoms are in a plane containing Pt. The position of the hydride was not located crystallographically, but the 1 H NMR spectrum of 3 , supports the presence of a terminal hydride that is cis to the carbonyl. The IR band of 3 at 2023 cm −1 which is assigned to ν(PtH), and the hydride cleavage reaction of 1 with CCl 4 , provide evidence for the PtH bond.

Dielectric and infrared reflectance studies of inorganic oxide glasses

Abstract The dielectric properties of several types of ionic oxide glasses, sodium trisilicate and a series of lithium fluoroborate glasses, have been measured in the infrared and far infrared by reflectance methods and analyzed together with those reported earlier which were obtained in the 1 × 10 2 to 2 × 10 9 Hz region at temperatures from 25 to 300 °C by bridge and time domain reflectance (TDR) techniques, Together, these provide nearly continuous data from low frequency through 1.35 × 10 4 Hz, with a gap from about 2 × 10 9 to 7.5 × 10 11 Hz. Interpolation through this range has been addressed by consideration of the behavior of ϵ′(ω) at the limits of the measured ranges. It has been found that the damped harmonic oscillator-modelled ϵ″ (ω) features in the infrared and far infrared lead to ϵ′(ω) curves which extrapolate to those ϵ′(ω) curves measured at lower frequency and provide the interpolation and effectively continuous spectra from low frequency through the infrared.