Luminescent Thermometers: From a Library of Europium(III) β‐Diketonates to a General Model for Predicting the Thermometric Behaviour of Europium‐Based Coordination Systems

Abstract

A new model with the aim to predict the temperature dependence of europium emission in coordination systems is presented. The model has been developed from a library of Eu3+ complexes of general formula EuL3A2, where L is a β‐diketone, and A is an ancillary ligand. Three possible deactivation channels have been considered: two competitive metal‐related terms describing the primary deactivation channels, i. e. back energy transfer and multiphonon quenching, and a third ligand‐related term to describe non‐radiative deactivation of the antenna triplet. As many parameters as possible are taken from measurable chemical‐physical properties, such as ligand triplet and multiphonon quenching energies. The other parameters have been deduced from selected EuL3A2 compounds and used as one‐size‐fits‐all values. The model proved to be very effective in describing the interplay between back energy transfer and multiphonon deactivation channels. Finally, the model has been implemented in a freeware standalone MATLAB application. Users need to input only the energy of the sensitizer triplet level and choose the coordinated quencher, if present. It simulates the range of applicability of the molecular thermometers and the shape of the thermometric sensitivity curve Sr employing as thermometric parameter either emission intensity or lifetime.

Nature of the Ligand-Centered Triplet State in Gd3+β-Diketonate Complexes as Revealed by Time-Resolved EPR Spectroscopy and DFT Calculations

“…Synthesis and characterization of the precursor P1 and ligands 1 and 2 (see Figure 1 ) and corresponding Gd 3+ complexes ( GdP1 , Gd1 , and Gd2 ) are reported in ref ( 6 ), while those of 3 and Gd3 are thoroughly described in ref ( 2 ). Emission spectra were collected with a Horiba Flurolog 3 spectrofluorometer.…”

“…GdP1 and Gd1 – Gd3 were embedded in polystyrene thin films and deposited via spin-coating on 10 × 10 mm 2 fused silica slides. 6 Temperature was controlled by using a Linkam THMS600 heating/freezing microscope stage coupled with the spectrofluorometer via optical fibers. We determined the nature of the emission performing time-gated experiments at 80 K in which a 300 μs delay after the excitation pulse was used to detect slow components (phosphorescence) of the emission spectra.…”

Composition–Thermometric Properties Correlations in Homodinuclear Eu3+ Luminescent Complexes

“… 14 Less extensive investigations, at variance, have been devoted to the temperature dependence of luminescent properties of discrete lanthanide β-diketonato complexes, 19 − 26 though these compounds, being easily processable, are suitable for the development of functional materials for temperature measurements. 27 − 29 Europium complexes with a β-diketonato triplet energy of around 20.000–25.000 cm –1 , 30 − 33 are suitable for temperature sensing between 223 and 373 K, an interval that covers the physiological window (298–323 K) and the working range of many integrated circuits. 21 , 26 , 34 The temperature-dependent luminescent properties of these complexes can be easily modulated by changing the lateral substituents on the β-diketonato ligand, as showed in a pioneering work by Sato and Wada.…”

Eu3+ as a Powerful Structural and Spectroscopic Tool for Glass Photonics

“…Eu 3+ has been largely used to demonstrate the spectroscopic dynamics in different optical materials and structures. The role of the Eu 3+ ion appears to be crucial in several papers concerning the study of energy-transfer processes, luminescence enhancement, optical hybrid filters [ 21 ], and thermometric measurements [ 22 ]. Eu 3+ is an excellent ion to develop red phosphors.…”