Jean-Claude Bunzli - Photophysical Properties of Lanthanide Dinuclear Complexes with P-Tert-Butylcalix[8]Arene

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  Bunzli,J.C.G., Froidevaux,P., Harrowfield,J.M. Inorganic   Chemistry 1993 32 (15) 3306-3311

  Abstract: The macrocyclic octaphenol   p-tert-butylcalix[8]arene (LH8) was reacted with lanthanide(III)   ions in dimethyl-formamide (DMF) containing triethylamine to   obtain both ****- and heterodinuclear neutral complexes of   composition [(Ln1:Ln2)LH2(DMF)5](DMF)n, with n = 4 (alpha-phase)   or 1.5 (beta-phase). ICP-AES determination of the Ln(III) content   shows a clear selectivity of the ligand for ions in the middle of   the lanthanide series. Luminescence measurements at 77 K suggest   that the two lanthanide(III) ions encompassed by the ligand are   in very similar environments with pseudo C3h symmetry. Small   differences in the crystal-field potential are evidenced between   the two crystalline phases and when a large ion (e.g Nd) is   encapsulated by the ligand. The presence of a low-lying   metal-to-ligand charge-transfer state (MLCT) in the Eu-containing   complexes at ca. 20 000 cm-1 induces unusual spectroscopic   properties. Very large absorption probabilities (approximately   10(-6)) have been determined for the Eu(III) transitions, and the   Judd-Ofelt theory for f-f transitions fails to explain the very   large value of the OMEGA2 parameter (448 X 10(-20) cm2). In DMF   solution, an efficient energy transfer from the ligand to Tb(III)   occurs and makes the Tb(III) calixarene complex an interesting   luminescent label

  Address (URL): WOS:A1993LN70300019