Spectra tetragonal symmetry

SrTiOs undergoes a structural change from cubic to tetragonal symmetry at —110° K. Additional lines appear [619] in the fluorescence spectrum of Eu3+ doped SrTiOs, as expected due to this change in symmetry. 

In D4h (tetragonal) symmetry there is only one unpaired electron in two degenerate orbitals of correct symmetry to give rise to n bonds with a n orbital of the porphyrin moiety [34]. The H NMR spectrum of Fe(protoporphyrin IX)-imidazole-cyanide is reported in Fig. 5.17 [35]. The free rotation of the imidazole ring about the metal-nitrogen bond, which is fast on the NMR timescale, simulates a tetragonal symmetry as far as the chemical shifts are concerned [36]. The four methyls are all downfield, though to a quite smaller value than in the case of... 

In case of trigonal symmetry, the is not split. However, the orbital degeneracy is lifted by the Jahn-Teller effect which, at higher temperatures, might distort the molecular complex. At lower temperatures, the Jahn-Teller distortion in some cases goes over into a static distortion, and a spectrum due to three magnetic complexes, each with tetragonal symmetry may be observed [53]. 

Uranium pentafluoride prepared in the above maimer is the low-temperature, form, which can be identified by its characteristic X-ray powder pattern. The single<rystal structure has been determined tetragonal symmetry, space group I42d(Z = 8), with eight-coordination and a geometry intermediate between a dodecahedron and a square antiprism. Uranium pentafluoride is air sensitive and disproportionates in water to give a precipitate of uranium tetrafluoride and a solution of uranyl fluoride. Consequently, UFs must be handled in an inert atmosphere. The near-infrared-visible spectrum of uranium pentafluoride in acetonitrile has been determined and is perhaps the most convenient characterization. 

Transannular interaction via the electron-delocalization mechanism was found, but lessened by 10-15% for the ligand superhyperfine splitting and 30-35% for the hyperfine splitting (62) in the epr spectrum. The crystal structure of [VOS2CNEt2)2] shows that the molecular core has the expected C2V symmetry [V-0 = 159.1(4), V-S = 138.7(2)-241.0(2) pm] (63). Magnetic and spectral data provided evidence for a tetragonal, pyramidal structure (VII) for these complexes. Like many other coordinatively unsaturated, metal... 

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