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Lanthanide Triple Helical Complexes with a Chiral Bis(benzimidazole)pyridine Derivative
European Journal of Inorganic Chemistry (2002)
  • Gilles Muller, San Jose State University
  • J. P Riehl
  • K. J Schenk, University of Lausanne
  • G. Hopfgartner
  • C. Piguet, University of Geneva
  • J.-C. G Bunzli

The ligand neopentyl 2,6-bis[(1-methylbenzimidazol-2-yl)]pyridine-4-carboxylate (L12) 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(L12)3]3+ complexes. The crystal structure of ligand L12 shows the expected trans-trans conformation of the tridentate binding unit. The ligand forms stable 1:3 complexes in anhydrous acetonitrile (logβ3 in the range 17.3−19.0, logK3 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 L12 appears to favour a 3ππ*-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 D3 local symmetry at the metal ion site. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002

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Gilles Muller, J. P Riehl, K. J Schenk, G. Hopfgartner, et al.. "Lanthanide Triple Helical Complexes with a Chiral Bis(benzimidazole)pyridine Derivative" European Journal of Inorganic Chemistry Vol. 12 (2002)
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