Characterization and photophysical properties of lanthanide macrocyclic complexes derived from (2,1)

The isolation and characterization of Ln(NO3)(3) complexes (Ln=La, Pr, Nd, Eu, Tb, Lu) with 2,3-benzo-1,4,7,13-tetraoxa-10-azacyclopenta-decane (L-1) and two of its N-substituted derivatives (L-2, L-3) are reported. Structura l information in the solid state is derived from spectroscopic data (vibrat ional, absorption, reflectance and luminescence spectra). Both ligand- and metal-centered luminescence of solutions of the complexes in oxygen-free an d anhydrous acetonitrile are investigated. Substitution of the N-proton of the crown ether enhances metal emission. Ligand L-2 displays a good antenna effect for Eu-III luminescence, while L-3 is especially effective in trans ferring energy from its triplet state onto the excited states of Tb-III. Th e Eu-III site in Eu(NO3)(3)L-2. 0.5C(2)H(5)OH . 1.5H(2)O possesses a low lo cal symmetry and a relatively long D-5(0) lifetime (1.01 ms). (C) 1999 Else vier Science Ltd. All rights reserved.