Low-symmetry Components Research Articles

ChemInform Abstract: CRYSTAL LATTICE EFFECTS ON THE ELECTRONIC SPECTRUM OF THE MANGANATE ION

AbstractDie polarisierten Elektronenspektren von MnOä Vdotierten Rbz 804‐, Cs2SO4‐ und KzCrO4‐Kristallen werden bei 4,2 K im Bereich von 10000 bis 40000 cm‐1 aufgenommen.

Single-crystal polarized electronic spectra of tetra- n-butylammonium tribromo(quinoline)cobaltate(II)

Single-crystal polarized electronic spectra of the pseudo-tetrahedral tetra- n-butylammonium tribromo(quinoline)cobaltate(II) have been recorded along three independent directions. To a first approximation the spectra have been assigned on a C 3vsymmetry, whereas a more detailed interpretation requires the introduction of C 1 low symmetry components. Such a behaviour has been compared with that of several other chromophores, both of nickel and cobalt, whose actual symmetry is C 1, whereas the gross features of the spectra have been accounted for on the basis of higher symmetries.

Crystal lattice effects on the electronic spectrum of the manganate ion

The polarised electronic spectra of MnO42– doped into crystals of Rb2SO4, Cs2SO4, and K2CrO4 have been recorded at 4·2 K in the range 10 000–40 000 cm–1. The different polarisation behaviour of the low-symmetry components of the 2T2 terms derived from the ligand-field and charge-transfer configurations is ascribed to differences in the magnitude of the spin-orbit interaction in the two types of configuration. From an analysis of the phonon sidebands in the ligand-field spectrum, comments are made about the phonon spectra of the host lattices. Shifts in the ligand-field and charge-transfer origins on changing the host lattice are also discussed.

Crystal polarised spectra, and electronic structures, of some pseudotetrahedral cobalt(II) complexes with ‘soft’ bonding ligands

The crystal polarised spectra of some pseudotetrahedral CoII complexes having chromophores [CoS2Cl2] and [CoP2X2](X = Br–, I–), have been recorded. The spectra may be assigned assuming an effective C2ν symmetry and spin–orbit coupling is found to be less important than the low-symmetry ligand field in modifying the electronic structure derived from Td symmetry. The sequence of components derived from Td symmetry is found to be: 4T1(F) : B1 < A2 < B2; 4T1(P) : B2 < A2 < B1. Crystal-field calculations fit the observed spectra only if parameters of the low symmetry components are treated as merely empirical parameters. Qualitative σ- and π-bonding parameters for the different donor ligands are derived and compared.

Behavior of the In-Plane g Tensor in Low-Symmetry d1 and d9 Systems with Application to Copper and Vanadyl Chelates

A general expression is developed for the orientations and magnitudes of the principal in-plane g values of low-symmetry d1 and d9 complexes considered as highly perturbed axial systems. The low-symmetry components of the ligand field cause participation of | 3z2 − r2〉 in the ground state and reorientation of the | xz〉, | yz〉 orbital set. The way in which these effects show up in the in-plane g ellipse is investigated for a number of possible bonding situations. A critical evaluation is made of the information which can be (and that which cannot be) obtained from the in-plane g values, and the observed g parameters from electron paramagnetic resonance of several copper and vanadyl chelates of Schiff's bases and ketoenolates are discussed in terms of the theory.

Rhodium as an impurity in single crystals of zinc tungstate

Single crystals of zinc tungstate grown by the Czochralski process are found to show dark coloration when pulled from rhodium or platinum-rhodium crucibles. Results of chemical analysis and electron spin resonance are presented which suggest this is due to rhodium entering the crystals. The electron spin resonance spectrum is consistent with Rh2+ in a crystal field having strong octahedral and weaker low-symmetry components.

901. The splitting of terms by low-symmetry ligand-field components

901. The splitting of terms by low-symmetry ligand-field components

Low-temperature optical absorption of ferrous fluosilicate crystals

Abstract The optical spectrum of the Fe2+ ion in an electric field of trigonal symmetry has been investigated down to liquid helium temperature. An account is given of the results, which suggest the operation of the dynamic Jahn-Teller effect and reveal the presence of a charge-transfer absorption and the action upon the latter of the low-symmetry component of the electric field. A structure which is present on the low-energy side of the main vibronic band, has been proved to be due to the crystal lattice rather than to the magnetic ions.

Magnetic Investigations of Spin-free Cobaltous Complexes. VI.1 Complexes Containing Phosphines and the Position of Phosphines in the Spectrochemical Series

Thorough study of the magnetic moments and the visible spectra of the complexes STACo(R/sub 3/P)/sub 2/X/sub 2/! (R = , X = Cl, Br, I and R = C/sub 6/H/sub 11/, X = Br, I) and of salts of two representatives of an anionic complex, STACo( /sub 3/P)Br/sub 3/!/sup -/ and STACo( /sub 3/P)I/sub 3/ i!/ sup -/ are reported. The effect of low-symmetry components in the ligand fields upon the magnetic and spectral properties is reported and discussed. By comparison of the data with previously reported data on other tetrahedral Co(II) complexes, it is shown that the two phosphines occupy a position in the spectrochemical series adjacent to toluidine and N/sup -/3/sub ./auth)>i