Substantial luminescence enhancement in ternary europium complexes by coordination of different ionic ligands

Abstract

We demonstrate in a general and comprehensive manner that a substantial enhancement of luminescence in europium complexes can be achieved by increasing ionic ligand diversity. The measured boosts in quantum efficiency ranged from 100% to 543%.

Europium Complexes: Luminescence Boost by a Single Efficient Antenna Ligand

“…The luminescence data for complexes of classes (v)–(vii) were obtained from previous works by our research group. 13,14,19…”

“…The computational strategy was the one described in our previous article, 19 in which we employed the semiempirical Sparkle/RM1 27 model, and the quantum chemical software MOPAC 2016. 35 Accordingly, the first step of the computational strategy was to calculate the fully optimized geometries of the chloride ligand europium complexes considered in this article.…”

“…We also measured in this article the luminescence properties of five other chloride complexes that had syntheses and characterizations recently reported by our research group: [EuCl 2 (TPPO) 4 ]Cl·3H 2 O, 20 [EuCl 2 (TTA)(TPPO) 3 ], 21 [EuCl 2 (DBM)(TPPO) 3 ], 21 [EuCl 2 (TTA)(BTFA)(TPPO) 3 ], 21 and [EuCl 2 (DBM)(BTFA)(TPPO) 3 ]. 21 Finally, to complete the luminescence databank for the combinatorial set of compounds, we included the previously determined luminescence properties of ternary europium(III) complexes of the types [Eu(β) 3 (TPPO) 2 ], 14,22,23 [Eu(β) 2 (β′)(TPPO) 2 ], 19 and [Eu(β)(β′)(β″)(TPPO) 2 ], 19 where β ≠ β′ ≠ β″ can be either 1-(2-thenoyl)-3,3,3-trifluoroacetone (TTA), 4,4,4-trifluoro-1-phenyl-1,3-butanedione (BTFA), or 1,3-diphenylpropane-1,3-dione (DBM). We then examined the effect of each type of ligand coordinated to the europium ion on the radiative decay rates using the chemical partition of A rad .…”

Europium complexes: choice of efficient synthetic routes from RM1 thermodynamic quantities as figures of merit

“…Mixed ligand europium complexes acquired importance aer a recent recognition of the fact that their luminescence properties, such as quantum yield, quantum efficiency, or radiative decay rate should be larger than the average of these properties for the respective same-ligand complexes. [12][13][14] Moreover, mixed ligand complexes may also exhibit triboluminescence, a property which seems to be somewhat correlated with a non-centrosymmetric crystal structure. 15 Syntheses of lanthanide complexes are frequently carried out by means of ligand displacement reactions.…”

“…Out of these six, we identied the ones that should be the best and the unfavorable routes; carried both of them out in our laboratory, and provedexperimentallythat they led to contrastive synthetic yields, all in line with the theoretical calculations. Finally, we sought to harden the geometries of these complexes in order to enhance their luminescent properties, 14 14 to allow us to arrive at two ligand displacement series in terms of coordination bond strength: one for ionic ligands and another for non-ionic ligandsboth theoretically predicted and experimentally proven.…”