Jean-Claude Bunzli - Highly luminescent, visible-emitting lanthanide macrocyclic chelates stable in water and derived from the cyclen framework

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  Zucchi,G., Ferrand,A.C., Scopelliti,R., Bunzli,J.C.G.   Inorganic Chemistry 2002 41  (9) 2459-2465

  Abstract: Two new tetraazamacrocyclic ligands   are designed with the aim of sensitizing the luminescence of   Tb(Ill) and Eu(Ill) ions in water:   L5{1,4,7,10-tetrakis[N-(phenacyl)carbamoylmethyl]-1,4,7,10-tetraazacyclododecan e}   and L6   {1,4,7,10-tetrakis[N-(4-phenylphenacyl)carbamoylmethyl]-1,4,7,10-tetraazacyclod odecane}.   These ligands react with lanthanide trifluoromethanesulfonates to   yield stable 1:1 complexes in water (log K = 12.89 +/- 0.15 for   EuL5). X-ray diffraction on [Tb(L5)(H2O)](CF3SO3)(3) (P (1) over   bar, a = 13,308(3) Angstrom, b = 14.338(3) Angstrom, c =   16.130(3) Angstrom, alpha = 101.37(3)degrees, beta =   96.16(3)degrees, gamma = 98.60(3)degrees) shows the Tb(III) ion   lying on a C-4 axis and being 9-coordinate, with one water   molecule bound in its inner coordination sphere. The absolute   quantum yields are determined in aerated water for the complexes   formed with ions used in fluoroimmunoassays (Ln = Sm, Eu, To, and   Dy). Large values are found for [Tb(H2O)(L5)](3+) and   [Eu(H2O)(L6)](3+), in line with the molecular design of the   receptors: 23.1% and 24.7%, respectively. The intense   luminescence of these ions results from efficient intersystem   crossing and L Ln energy transfer processes, as well as from a   suitable shielding of the emitting ions from radiationless   deactivation

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