Jean-Claude Bunzli - Deciphering Three Beneficial Effects of 2,2 '-Bipyridine-N,N '-Dioxide on the Luminescence Sensitization of Lanthanide(III) Hexafluoroacetylacetonate Ternary Complexes

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      Eliseeva,S.V., Pleshkov,D.N., Lyssenko,K.A., Lepnev,L.S.,   Bunzli,J.C.G., Kuzmina,N.P. Inorganic Chemistry  2011 50 (11) 5137-5144

      Abstract: Lanthanide hexafluoroacetylacetonate   ternary complexes with 2,2'-bipyridine-N,N'-dioxide,   [Ln(hfa)(3)(bpyO2)], were synthesized for Ln = Eu, Gd, Tb, and Lu   and fully characterized by elemental, thermal, and   mass-spectrometric analyses. The X-ray crystal structure of   [Eu(hfa)(3)(bpyO2)] center dot 0.5C(6)H(6) reveals an   octa-coordinate metal ion lying in a severely distorted trigonal   dodecahedron geometry; the Eu-O distances lie in the range   2.36-2.44 angstrom with no significant difference between hfa and   bpyO2. angstrom detailed comparative photophysical investigation   has been carried out to determine the exact influence of the   introduction of bpyO2 in the inner coordination sphere of the   metal ion in replacement of the two water molecules in   [Ln(hfa)(3)(H(2)O)(2)]center dot While this replacement is   detrimental for Tb, it leads to a 15-fold increase in the overall   quantum yield for Eu. This large improvement originates from (i)   a better sensitization efficiency, the ancillary ligand being   responsible for 3/4 of the energy transfer, (ii) elimination of   nonradiative deactivation pathways through'harmonics of O-H   vibrations, and (iii) reduction in the radiative lifetime. The   latter influence is rarely documented, but it accounts here for a   approximate to 25% increase in the intrinsic quantum yield, so   that more attention should be given to this parameter when   designing highly luminescent lanthanide complexes

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