Jean-Claude Bunzli - Structural and Luminescence Study of Europium and Terbium Tris(Bromate) Nonahydrates

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  Publication Details (including relevant citation   information):

  Moret,E., Nicolo,F., Bunzli,J.C.G., Chapuis,G. Journal of the   Less-Common Metals 1991 171 (2)   273-300

  Abstract: The crystal structures of   Eu(BrO3)3.9H2O and Tb(BrO3)3.9H2O were determined at 200 K   (europium, terbium) and 295 K (europium) from single-crystal   X-ray diffraction. The two hydrates crystallize in the hexagonal   space group P6(3)mc (ITC number 186) with Z = 2. Cell parameters   at 200 K are a = b = 11.714(3), c = 6.687 angstrom for europium,   and a = b = 11.723(1), c = 6.669(1) angstrom for terbium; at 295   K, a = b = 11.794(2) and c = 6.754(2) for europium. Least-squares   refinements performed with 456 (europium, 200 K), 405 (europium,   295 K) and 439 (terbium, 200 K) unique reflections yielded final   R(F) values of 0.026, 0.026 and 0.015 respectively. The   coordination polyhedra around the Ln(III) ions have C3v symmetry.   Hydrogen atoms could be located for the terbium hydrate.   Differences between the europium and terbium structures arise in   the Ln-O distances and in the slight disorder experienced by one   oxygen atom of the bromate ion. High-resolution luminescence   spectra of both the europium enneahydrate and the deuterated   solvate reveal a symmetry lowering at the metal ion site from an   almost ideal D3h symmetry at 295 K to C3v at 77 K. The latter   symmetry was ascertained on the basis of polarized luminescence   spectra obtained with single crystals. In addition, luminescence   spectra at 4.2 K disclosed the effects of a phase transition   generating four distinct chemical sites, one with a symmetry   close to D3h and the three others with a symmetry close to C2v.   Finally, luminescence lifetimes of the 5D0 (europium) and 5D4   (terbium) levels in the hydrates and deuterated solvates are   presented and used to determine the quenching rates of the OH   oscillators

  Address (URL): WOS:A1991GE14500013