Jean-Claude Bunzli - Complexes of Lanthanoid Salts with Macrocyclic Ligands .42. Energy-Transfer Processes in Lanthanide Dinuclear Complexes with P-Tert-Butylcalix[8]Arene - An Example of Dipole-Dipolar Mechanism

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  Froidevaux,P., Bunzli,J.C.G. Journal of Physical   Chemistry 1994 98 (2) 532-536

  Abstract: The study of energy-transfer processes   between Tb(III) and various Ln(III) ions (Ln = Ho, Nd, Eu) in   dinuclear complexes of p-tert-butylcalix[8]arene, [(Tb(x)Ln(2-x))   (LH(2)) (DMF)(5)]-4DMF, is reported. Easily available crystals   allow an extended work on these transfers. The compounds contain   isolated molecules, so that a simple model accounts for the   observed luminescence decays. Only two types of interacting Tb-Ln   pairs need to be taken into account, one at 3.7 Angstrom and the   other at 11 Angstrom. A rate equation is developed to quantify   the energy transfer, and the analyzed data give an interaction   strength sequence proportional to the overlap integral, F-Tb-Ho   > F-Tb-Nd > F-Tb-Eu. Moreover, the good fits obtained point   unambiguously to a dipole-dipolar character of the   energy-transfer processes. The low-lying ligand-to-metal   charge-transfer state (LMCT) increases the absorption   probabilities of Eu(III) f-f transitions considerably, and the   resulting quasi-allowed D-5(0)<--(CF0)-F-7 t an important role   in the energy-transfer process. This feature permits us to assign   a dipolar character to the interaction responsible for the energy   transfer. The low-lying LMCT state also induces a strong   intramolecular Eu-Eu interaction

  Address (URL): WOS:A1994MR53500030

 

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