Study on photophysical properties of Eu(III) complexes with aromatic beta-diketones Role of charge transfer states in the energy migration

: Markus Räsänen, Harri Takalo, Jaana Rosenberg, Joonas Mäkelä, Keijo Haapakka, Jouko Kankare

Publisher: ELSEVIER SCIENCE BV

: AMSTERDAM; PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS

: 2014

: Journal of Luminescence

: J Lumin

: 146

: 211

: 217

: 7

: 0022-2313

DOI: https://doi.org/10.1016/j.jlumin.2013.09.076

We synthesized a set of aromatic beta-diketones and measured the photophysical properties of their europium(III) complexes. According to these photophysical properties, the europium complexes can be divided into two groups: the complexes with or without the freely rotating amino-group (FRAG). On the basis of the experimental results, it can be concluded that in the FRAG complexes, the ligand-centered excitation energy is most probably transferred from a ligand to a coordinated europium via the intraligand charge transfer (ILCT) state. The temperature dependency of the lifetimes of the emissive D-6(0) state revealed that in the FRAG complexes, the energy of the emissive 5130 state is back-transferred to the ligand-to-metal charge transfer (LMCT) state and in the non-FRAG complexes, to the triplet state of the ligand. The most efficient complex synthesized was the europium complex of carbazole derivative L-6 with the quantum yield of 47% and molar absorption coefficient of 70,400 M-1 cm(-1). (C) 2013 Elsevier B.V. All rights reserved.