Illuminating the Intermolecular vs. Intramolecular Excited State Energy Transfer Quenching by Europium(III) Ions

Abstract

Bright lanthanide-based probes rely on sensitised lanthanide luminescence. The outcome of the excited state energy transfer cascade -from sensitiser chromophore to lanthanide(III) ion -should be the population of the lanthanide excited state with an efficiency equal to unity. This is rarely the case, and this is a particular problem for europium(III) due to the low energy of the Eu(II)/Eu(III) redox couple. Thus, photoinduced electron transfer quenching can be an efficient drain for the excited state energy, reducing the brightness of a probe. Here, the effect of intramolecular PeT in a lanthanide-based probe is [a]

π‐Expanded Thioxanthones – Engineering the Triplet Level of Thioxanthone Sensitizers for Lanthanide‐Based Luminescent Probes with Visible Excitation

“…As no coordinating atoms are present in the π‐extended thioxanthones, we must rely on a rigid ligand backbone to ensure that the antenna chromophore will collide with the lanthanide centre during the excited state lifetime. We recently showed that this is not the best design principle, and indeed, the 1 H NMR spectra in Figure show that the Eu. L 1 and Eu.…”

“…A prerequisite for efficient sensitization of lanthanide(III) luminescence is that the chromophore and the lanthanide centre are in contact . As no coordinating atoms are present in the π‐extended thioxanthones, we must rely on a rigid ligand backbone to ensure that the antenna chromophore will collide with the lanthanide centre during the excited state lifetime.…”

“…Clearly the population of the terbium(III) centre in Tb. L 1 must be inefficient, despite favourable energetics . In the europium(III) complexes Eu.…”

Quinolone Complexes with Lanthanide Ions: An Insight into their Analytical Applications and Biological Activity

“…Thus, the excitation and emission wavelengths are characteristic of the ligand and the lanthanide ion, respectively. The energy-transfer process can be intramolecular or intermolecular [82].…”

“…In cases where only two quinolone molecules are bound to the central ion, other ligands, such as 1,4,7,10tetraazacyclododecane-1,4,7-triacetic acid (DO3A) [84] or tri-n-octylphosphine oxide (TOPO), have The intermolecular process implies no chelate formation; the energy is transferred from the triple state of an organic compound, such as an aromatic aldehyde or ketone, to the 4f electrons of the lanthanide ion. The process is diffusion controlled, induced through collisional quenching and takes place after the encounter between the donor and the acceptor [82].…”