Synthesis, crystal structures, and photophysical properties of lanthanide complexes containing pyrrole-derivatized carboxylate ligands

Abstract

Two pyrrole-deriviatized carboxylic acids [L 1 = 1-methylpyrrole-2-carboxylate] and [L 2 = N-methyl-3-indoleglyoxylate] were used as ligands to prepare six lanthanide coordination compounds [(L 1) 3Ln] n (Ln = Eu, 1; Gd, 2; Tb, 3) and [(L 2) n-Ln(NO 3)(MeOH) 2] n (Ln = Eu, 4; Gd, 5; Tb, 6). These complexes have been synthesized and structurally characterized by single-crystal X-ray diffraction. The phosphorescence behavior of the ligands in the Gd 3+ complexes show that modification of the ligands can tune the triplet energy levels of the ligands so that they match the 5D 0 energy level of Eu 3+ and the 5D 4 energy level of Tb 3+; thus, the energy transfer efficiency from antenna to Eu 3+ and Tb 3+ is improved, and the Eu 3+ and Tb 3+ emission intensity is enhanced. This concept can be applied towards improving the luminescent properties of Ln 3+ complexes by the modification of coordinating ligands. © Wiley-VCH Verlag GmbH & Co. KGaA, 2007.