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-azacyclo-penta-decane (L1) and two of its N-substituted derivatives (L2, L3) are reported. Structural information in the solid state is derived from spectroscopic data (vibrational, absorption, reflectance and luminescence spectra). Both ligand- and metal-centered luminescence of solutions of the complexes in oxygen-free and anhydrous acetonitrile are investigated. Substitution of the N–proton of the crown ether enhances metal emission. Ligand L2 displays a good antenna effect for EuIII luminescence, while L3 is especially effective in transferring energy from its triplet state onto the excited states of TbIII. The EuIII site in Eu(NO3)3L2·0.5C2H5OH·1.5H2O possesses a low local symmetry and a relatively long 5D0 lifetime (1.01 ms).