Eu(III) and Tb(III) Complexes with the Nonsteroidal Anti-Inflammatory Drug Carprofen: Synthesis, Crystal Structure, and Photophysical Properties

Abstract

Two new lanthanide complexes with general formula [Ln₂(carprofen)₆­(DMF)₂] (Ln = Eu (<b>1</b>), Tb (<b>2</b>), DMF = <i>N</i>,<i>N</i>-dimethylformamide, carprofen = 6-chloro-α-methylcarbazole-2-acetic acid) have been synthesized by a hydrothermal method. Complex <b>1</b> was characterized by single-crystal X-ray diffraction (XRD), and it was found to crystallize in the monoclinic space group <i>C</i>2<i>/c</i>. The coordination of the ligand to the lanthanide ion has been investigated by Fourier-transform infrared (FTIR) spectra and ultraviolet–visible (UV–vis) absorption spectra. Complex <b>1</b> emits red light, but the antenna effect of the ligand is not effective, whereas complex <b>2</b> presents intense green emission with effective energy transfer from the ligand. The different performance of the two complexes is related to the energy matching between the excited states of the lanthanide ion and the triplet state of the ligand. The intramolecular energy transfer mechanisms are also discussed