Role of LMCT States in Luminescence Excitation Processes in Europium Indolecarboxylates

• Published in: Optics and spectroscopy Vol. 131; no. 10; pp. 1103 - 1111
• Main Authors: Tsaryuk, V. I., Zhuravlev, K. P.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.10.2023; Springer Nature B.V
• Subjects: Acetates; Carboxylates; Charge transfer; Electron states; Energy transfer; Europium; Europium compounds; Excitation spectra; Lasers; Ligands; Luminescence; Optical Devices; Optics; Photonics; Physics; Physics and Astronomy; Quenching; Eu; LMCT; luminescence; indolecarboxylate; π-excessive heterocycle; Tb
• ISSN: 0030-400X; 1562-6911
• DOI: 10.1134/S0030400X23100259

The luminescence excitation energy transfer in europium and terbium indole-3-carboxylates, indole-3-acetates and indole-3-propionates as well as ternary indolecarboxylates containing 1,10-phenanthroline and 2,2'-bipyridine molecules have been studied. The luminescence excitation spectra, the lifetimes of the 5 D 0 (Eu 3+ ) and 5 D 4 (Tb 3+ ) states, and the luminescence intensity are analyzed. The decisive role of ligand-metal charge transfer (LMCT) states in the quenching of the luminescence of europium aromatic carboxylates containing a π-excessive pyrrole or indole fragment is demonstrated. Most europium compounds are characterized by quenching due to the depopulation of the 5 D 0 state of the Eu 3+ ion through the low-energy LMCT state. But in some ternary compounds, the LMCT state being of higher energy participates in the nonradiative depopulation of the excited electronic states of the ligand.