Electron Spin Resonance of Photochromic β-Tetrachloro-α-ketonaphthalene

A triplet ESR spectrum has been observed in a powdered sample of β 2,3,4,4-tetra-chloro-α-ketonaphthalene after UV irradiation. The spectrum could be reproduced by computer simulation using an anisotropic g-tensor (gxx = 2.00950, gyy = 2.00280, gzz = 2.00232) and zero-field splitting parameters D’ and E’ of 99 and 2.3 gauss respectively. The results are discussed in terms of the earlier proposed photodissociation into a naphthoxyl radical and a chlorine atom

Electron Spin Resonance of Photochromic β-Tetrachloro-α-ketonaphthalene

A triplet ESR spectrum has been observed in a powdered sample of β 2,3,4,4-tetra-chloro-α-ketonaphthalene after UV irradiation. The spectrum could be reproduced by computer simulation using an anisotropic g-tensor (gxx = 2.00950, gyy = 2.00280, gzz = 2.00232) and zero-field splitting parameters D’ and E’ of 99 and 2.3 gauss respectively. The results are discussed in terms of the earlier proposed photodissociation into a naphthoxyl radical and a chlorine atom

Relativistic and correlation effects on molecular properties - the interhalogens CIF, BrF, BrCI, IF, ICI and IBr

The effect of relativity on the properties of the interhalogens ClF, BrF, BrCl, IF, IBr, and IBr is studied by comparing relativistic and nonrelativistic calculations. Bond lengths, harmonic frequencies, and dissociation energies show that the bond is weakened in the relativistic formalism. Relativity increases the electric dipole moment whereas the electric quadrupole moment and dipole polarizability display an irregular behavior. The relativistic contributions to the electric dipole and quadrupole moment of the iodine containing molecules are 10%–20% of the total value, whereas the contributions in the other molecules cannot be neglected. The value of the electric quadrupole moment is dominated by the relativistic contributions

Heisenberg exchange enhancement by orbital relaxation in cuprate compounds

We calculate the Heisenberg exchange J in the quasi-2D antiferromagnetic cuprates La2CuO4, YBa2Cu3O6, Nd2CuO4 and Sr2CuO2Cl2. We apply all-electron (MC)SCF and non-orthogonal CI calculations to [Cu2O11]18-, [Cu2O9]14-, [Cu2O7]10- and [Cu2O7Cl4]14- clusters in a model charge embedding. The (MC)SCF triplet and singlet ground states are well characterized by Cu2+ (dx2-y2) and O2-. The antiferromagnetic exchange is strongly enhanced by admixing relaxed (MC)SCF triplet and singlet excited states, in which a single electron is transferred from the central O ion to Cu. We ascribe this effect to orbital relaxation in the charge transfer component of the wave function. Close agreement with experiment is obtained.Comment: publishe

Theo Thole, an unusual man

After a word of welcome some personal remarks are made on Thee's start in theoretical chemistry, on his remarkable achievements thereafter and on his very special qualities as a friend and colleague

Broken Orbital-Symmetry and the Description of Hole States in the Tetrahedral [CrO4]= Anion. I. Introductory Considerations and Calculations on Oxygen 1s Hole States

The localization of holes in systems containing spatially equivalent sites is discussed in terms of a simple one-particle model in which quantum mechanical delocalization effects compete with essentially classical polarization or dielectric relaxation effects. The predictions of the model for a tetrahedral system like CrO4= compare favourably with the results of symmetry unrestricted SCF calculations on O1s hole states. The connection with a CI treatment using symmetry-restricted MOs is discussed. The calculated ionization energies are finally compared with XPS measurements on Na2CrO4. To this and the crystal surrounding of the CrO4= anion has been represented by a point charge model and the ensuing Madelung field was included in the SCF calculations. In contrast to the Td restricted result of 551.4 eV, the completely localized C3v result of 532.6 eV is in satisfactory agreement with the experimental data which are found around 530.0 eV.