Stanley Abramowitz

Matrix‐Isolation Studies of the Infrared Spectra of the Free Radicals CCl3 and CBr3

CCl3 has been stabilized both by the reaction of lithium atoms with CCl4 in an argon matrix at 20°K and by the vacuum‐ultraviolet photolysis of HCCl3 or of DCCl3 in an argon or a nitrogen matrix at 14°K. The analogous techniques have been found to lead to the stabilization of CBr3. The product spectra obtained in the lithium‐atom experiments are considerably simpler than those obtained in the previous studies of the reaction of lithium atoms with matrix‐isolated CX4. In the vacuum‐ultraviolet photolysis experiments, DCCl2, HCBr2, and CBr2 have also been observed. The absorption frequencies and contours obtained for ν3 of CCl3 and of CBr3 are independent of the method used to produce these species, suggesting that lithium atoms and their reaction products do not appreciably perturb the degenerate stretching mode of either CCl3 or CBr3. Despite yields of these species comparable to those previously reported, absorptions at 674 and at 582 cm−1, previously attributed to ν1 of CCl3 and CBr3, respectively, are ...

Force Fields for the Boron Trihalides

The method of Edgell and Moynihan for determining Coriolis zeta constants from the infrared band contours of degenerate vibrational modes was verified for selected molecules and was then applied toward computing the zeta values of the E symmetry vibrations of the boron‐trihalide molecules. Since it is not feasible to define unique potential functions for the BX3 species from only frequency data, general force fields were determined for the series by combining both the Coriolis zeta constants and the observed isotopic frequency data in a least‐squares refinement scheme. The final force fields indicate that the sensitive stretch—bend interaction constant is a significantly large negative quantity that decreases as the series progresses from BF3 to BI3.

Force Fields for Group IV Tetrafluorides and Group V Trifluorides

The Coriolis zeta constants of the degenerate modes of SiF4, GeF4, NF3, PF3, and AsF3 were obtained from infrared‐band contour measurements. These Coriolis coupling data provided the necessary constraints for determining unique force fields for the F2 and E symmetry species of the XF4 and XF3 molecules, respectively. In an attempt to limit the force field for the A1 species of the XF3 molecules, the rotational distortion constants, which are functions of both the A1 and E species force constants, were calculated for a range of values of the F12 interaction force constant. For the purpose of this calculation, the E species force constants that were determined from Coriolis coupling data were held fixed. For NF3, a satisfactory value of F12 was obtained using the rotational distortion data. However, the rotational distortion data were not useful in fixing the A1 species force fields for PF3 and AsF3.

STRUCTURE OF THE ALKALI HYDROXIDES. V. THE INFRARED SPECTRA OF MATRIX- ISOLATED RbOH, RbOD, NaOH, AND NaOD.

The infrared spectra of matrix‐isolated RbOH, RbOD, NaOH, and NaOD have been observed. Both the alkali‐metal–oxygen stretch ν1 and the bending mode ν2 have been assigned for each species. The metal–oxygen stretching mode is found at 354.4, 345, 431, and 422 cm−1 for RbOH, RbOD, NaOH, and NaOD, respectively; the bending mode ν2 is observed at 309.0, 229, 337, and 250 cm−1, respectively. Combination of the results of this study with the microwave measurements for RbOH and RbOD indicates an essentially linear structure for these species. The isotope shift for ν2 observed in NaOH coupled with reasonable bond lengths indicates an equilibrium configuration of NaOH which probably does not deviate significantly from linearity. The assumption of a linear model with a harmonic bending potential yields force constants of 0.046 × 10−18 and 0.053 × 10−18 Nm (0.046 and 0.053 mdyn·A) for RbOH and NaOH, respectively. These results are consistent with our previously reported results for CsOH.

Potential function for axial–equatorial fluorine atom exchange in PF5, AsF5, and VF5

Gas‐phase Raman spectra of the ν7 fundamentals of AsF5 and VF5 were recorded for spectral resolutions approaching 1.5 cm−1. The vibrational transitions associated with ν7 for these systems, as well as for PF5, were interpreted in terms of a two‐dimensional anharmonic potential function constrained to a double minimum form for the motions leading to axial–equatorial fluorine atom exchange. The intramolecular exchange barrier heights, determined by the double minimum potentials, lie between 1139 and 995 cm−1 (3.26 to 2.84 kcal/mol where 1 kcal/mol=4.184 kJ/mol) for PF5, 864 and 755 cm−1 (2.47 and 2.16 kcal/mol) for AsF5, and 593 and 428 cm−1 (1.54 and 1.22 kcal/mol) for VF5. A discussion of the dynamics of the fluorine atom interchange pathways suggests that these trigonal bipyramidal (D3h) molecules form C4v intermediates by initially displacing the equatorial fluorine atoms and then by mixing in the axial fluorine distortions as the intramolecular exchange proceeds.

FORCE FIELDS FOR SOME GROUP VI HEXAFLUORIDES.

The Coriolis zeta constants were determined for the infrared‐active F1u modes of SF6 and TeF6 from gas‐phase band contour measurements. The Coriolis data were applied toward determining the general force fields for thes Group VI hexafluorides.

Structure of the Alkali Hydroxides. II. The Infrared Spectra of Matrix‐Isolated CsOH and CsOD

The infrared spectra of matrix isolated CsOH and CsOD have been observed. Both the CsO stretching and the bending mode have been assigned for each species. The Cs–O stretching mode ν2 is observed at 335.6 and 330.5 cm−1 for CsOH and CsOD, respectively; the bending mode ν2 is observed at 306 and 226 cm−1, respectively. Combination of the infrared results with previous microwave measurements indicates that the equilibrium configuration of CsOH probably does not deviate significantly from linearity. The assumption of a linear model with a harmonic bending potential leads to a bending force constant of 0.047 mdyn· A.

Measurement of Infrared Band Contours in Solution

Infrared band contours have been observed for nonpolar molecules in the liquid phase and in solution in nonpolar solvents with a spectral slitwidth of about 1 cm—1. A criterion was established for measuring the relative amounts of Lorentzian and Gaussian character to a band. It was found that symmetric bands were Lorentzian and that asymmetry appeared as a consequence of intramolecular effects that could be shown to be present in the vapor‐phase spectrum.

Potential function for the ν7 vibration of phosphorus pentafluoride

Author Institution: Bell Laboratories, Murray Hill; Inorganic Materials Research Division Lawrence Berkeley Laboratory and Chemistry Department, University of California; Inorganic Materials Research Division Lawrence Berkeley Laboratory and Chemistry Department, National Bureau of Standards; Laboratory of Chemical Physics, National Institute of Arthritis Metabolism and Digestive Diseases

Infrared spectra of matrix isolated FeO2: Evidence for a cyclic iron-oxygen complex

Abstract Infrared matrix isolation techniques were used to study the reaction of Fe(vapor) with oxygen molecules. For various isotopically enriched oxygen samples, spectral transitions at 945.9, 930.8 and 911.4 cm−1 were assigned on the basis of their relatively large frequency shifts to the OO stretching modes of Fe16O18O and Fe18O2, respectively. The low frequency FeO stretching modes were assigned to features at 517.1, 508.1 and 494.0 cm−1 for the same three isotopically substituted dioxygen complexes. Both the frequency behavior and intensity patterns involving the dioxygen ligand indicate a cyclic isosceles model for the FeO2 system.