Showing papers on "Tetrahedral molecular geometry published in 1974"

ESR and Optical Absorption Studies of Various Bis(N-salicylidenealkylaminato)copper(II) Complexes with Tetrahedrallydistorted Coordination Geometry

Abstract: The ESR and visible absorption spectra of a number of bis(N-salicylidenealkylaminato)copper(II) complexes with different kinds of alkyl groups were measured in toluene. The coordinations of these complexes in toluene are distorted towards a tetrahedral geometry to varying extents; the relationship between the degree of the distortion and the ESR and visible absorption parameters was systematically investigated. Especially, the experimental fact that the absolute values of the hyperfine coupling constant with the copper nucleus decrease with an increase in the degree of distortion was discussed. A configurational equilibrium between two species with different degrees of the distortion was found to exist for the complexes with R=isopropyl and cyclohexyl in toluene.

An electron spin resonance study of dimeric, trimeric, and tetrameric paramagnetic silver atom clusters

Abstract: The low temperature γ-irradiation of frozen benzene solutions containing AgClO4 leads directly to the formation of the paramagnetic species Ag2 +, no Ag0 centre being detected. When benzene or toluene solutions containing AgBF4 were similarly treated and the matrix carefully annealed, well-resolved E.S.R. spectra attributed to paramagnetic clusters containing three and four equivalent silver atoms were detected. The lack of resolved anisotropy in the spectrum of the trimer and tetramer are thought to argue in favour of a triangular and tetrahedral geometry respectively rather than linear chains.

Collision-broadened line widths of tetrahedral molecules—I. Theoretical formulation

Abstract: A theoretical formulation is presented within the framework of Anderson-Tsao- Curnutte theory for calculating the half-widths of spectral lines belonging to tetrahedral molecules. The importance of tetrahedral symmetry in the change distribution and in the wave functions is emphasized. Expressions for the interruption functions S 2 (b) have been derived for octopole-dipole, octopole-quadrupole, octopole-octopole, octopole-hexadecapole, hexadecapole- hexadecapole, anistropic dispersion interactions as well as for an assumed overlap interaction potential. The earlier theoretical work of Tejawni and Yamamoto and Hirono is shown to be inappropriate for molecules of tetrahedral symmetry.

Investigations of structure and conformation. Part IV. An electron spin resonance and INDO molecular orbital study of the influence of electronic interactions upon radical geometry

Abstract: INDO MO Calculations provide support for conclusions based on e.s.r. hyperfine splittings that α-hydroxyalkyl radicals are bent at the radical centre and that α,β-dihydroxy- and α-hydroxy-β-ammonio-ethyl radicals preferentially adopt an almost eclipsing conformation; evidence is also obtained that in this conformation there is distortion from tetrahedral geometry at the β-carbon (this explains the unusually low β-hydrogen splittings observed). In contrast, the radical ·CH2·CH2OH is planar at the radical centre and prefers a conformation in which the β-C–O bond subtends an angle of 90° with the orbital of the unpaired electron.

Non-Empirical INDO-MO Calculations on Some Vanadium(IV) Halides

Abstract: ODIN, a non-empirical INDO-MO scheme, has been used to determine the ground state electronic configurations for the tetrahedral molecules, VCl4 and VBr4. A 2 E ground state was obtained for both molecules. The Photoelectron spectrum and the electronic spectrum have been calculated for VCl4, and a satisfactory correlation with the corresponding experimental data was made. Also, ODIN was employed to evaluate electronic transition energies and the photoelectron spectrum of VBr4.

Applications of a simple molecular wavefunction. Part 4.—The force fields of BH–4, CH4 and NH+4

Abstract: The simple harmonic force constants for a valence force field have been computed using Frost's Floating Spherical Gaussian Orbital (FSGO) method for the tetrahedral molecules BH–4, CH4 and NH+4 and comparison has been made with the experimental values. In general the agreement is good for BH–4, less good for CH4 and poor for NH+4. The calculated main force constants are larger than the experimental ones. The signs of the bond–bond, angle–angle and bond–angle cross-term constants are discussed. It is found that the signs correspond to the change in geometry expected on dissociation to two hydrogens and a triatomic species. This is true experimentally without exception and theoretically with one possible exception. However, dissociation products expected theoretically are not the same as those that would, in fact, be formed. This accounts for the differences between theory and experiment in this respect in almost all instances. It suggests that an open-shell calculation is required.

Configurations of weak interactions from vibrational perturbations in tetrahedral XY4 molecules or ions

Abstract: Approximate methods are described for estimating changes in stretching force constants due to weak interactions involving tetrahedral molecules or ions from the shifts in their vibration frequencies. These methods are used to discuss published vibrational data for the C3v species Na[Co(CO)4] and [(H15C7)3HN][GaCl4] in solution, which are deduced to be apical ion-pairs from the size of the force-constant changes. Approximate formulae are also given for the stretching frequencies of trigonal-planar XY3 and octahedral XY6 molecules for stretching-force-constant perturbations which lower their symmetry to C2v and D4h respectively.

Computer simulation of some reactions of energetic tritium and fluorine atoms

Abstract: A six body atom + tetrahedral molecule model of hot atom reactions is described and used to study the reactions of hot T and F atoms with CH4 and CF4. Excitation functions for all observed reactions are given for the energy range 0–30 eV. The functions are compared with the data available from recoil atom studies and found to be qualitatively consistent with the principal features of the experimental results. Of particular interest is the very high degree of internal excitation deposited in products following substitution reactions by hot F atoms with molecules containing at least two heavy atoms or groups. Using the F + CH2F2 system, it is shown that some substitution events occur in which more than 9.4 eV is deposited in the product molecule.

Mean Amplitudes of Vibration for Tetrahedral Molecules and Ions

Abstract: Abstract Mean amplitudes of vibration for 38 tetrahalides and 15 tetraoxides have been computed at temperatures T = 0° K , T = 298.15 °K and T=500°K employing most recent vibrational data. Müller's method has been followed in solving the two dimensional Cyvin's secular determinant. The results have been briefly discussed.