Jean-Claude Bunzli - Lanthanide triple helical complexes with a chiral bis(benzimidazole)pyridine derivative

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  Publication Details (including relevant citation   information):

  Muller,G., Riehl,J.P., Schenk,K.J., Hopfgartner,G., Piguet,C.,   Bunzli,J.C.G. European Journal of Inorganic Chemistry  2002 (12) 3101-3110

  Abstract: The ligand neopentyl   2,6-bis[(1-methylbenzimidazol-2-yl)]pyridine-4-carboxylate (L-12)   has been synthesised to test the effect of the chiral neopentyl   ester group in the 4-position of the pyridine ring on (i) the   helical wrapping, (ii) the diastereomeric induction and (iii) the   thermodynamic and photophysical properties of the   [Ln(L-12)(3)](3+) complexes. The crystal structure of ligand L-12   shows the expected trans-trans conformation of the tridentate   binding unit. The ligand forms stable 1:3 complexes in anhydrous   acetonitrile (logbeta(2) in the range 13.3-19.0, logK(3) in the   range 2.9-4.6). The triple helical structure in solution is   responsible for the four times larger specific rotary dispersion   measured in the complexes. Circularly polarised luminescence of   the Eu triple helical complex displays a weak effect, suggesting   a small diastereomeric excess in solution. Ligand L-12 appears to   favour a 3pi*-to-Ln energy transfer process for Eu, but   temperature-dependent nonradiative processes lead to a very small   quantum yield. High-resolution luminescence spectra indicate that   the Eu complex has a distorted D-3 local symmetry at the metal   ion site. (C) Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany,   2002

  Address (URL): J INORG CHEM