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© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.

Abstract

In this paper we describe the results of the influence of temperature in the range of 280–340 K on the luminescence of bimetallic Eu/Tb complexes with N-heterocyclic ligand L based on 2,2′-bipyridyldicarboxylic acid in acetonitrile. The experiments were carried out for systems with various Eu/Tb ratios. The stability of the complexes of the ligand L with metal M (Eu or Tb) was determined using spectrophotometric titration in acetonitrile solutions. The LM complexes’ stability constants were found to be typical for these systems; however, the stability of Eu complex is slightly higher than that for Tb. Along with rising temperature, we observed a decrease in Tb emission intensity and, at the same time, an enhancement in Eu luminescence. An explanation of Eu luminescence enhancement involves the appearance of charge transfer states, bands of which can be observed in the Eu luminescence excitation spectra as difference spectra measured with two close temperatures. The unusual Eu luminescence enhancement upon heating was observed for the first time for the complex with tetradentate O,N-type heterocyclic diamide ligand L, while an inverse phenomenon was observed with the Tb luminescence. The Eu luminescence enhancement was found earlier for various carboxylate complex salts, but not for heterocyclic coordination complexes. This allows the construction of a ratiometric luminescent thermometer in the range of 280–340 K using the ratio of luminescence intensities for Eu and Tb. The stability constants for the individual Eu and Tb complexes help us to understand the equilibrium in L:Tb:Eu complex system and shed light on plausible speciation in solution.

Details

Title
Bimetallic Eu/Tb Complexes for Ratiometric Temperature Sensing with Unusual Enhancement of Eu Luminescence with Temperature
Author
Kharcheva, Anastasiia V 1   VIAFID ORCID Logo  ; Bozhko, Alena A 1 ; Sokolovskaya, Yulia G 1 ; Borisova, Nataliya E 2   VIAFID ORCID Logo  ; Ivanov, Alexey V 2 ; Patsaeva, Svetlana V 1   VIAFID ORCID Logo 

 Faculty of Physics, Lomonosov Moscow State University, Moscow 119991, Russia 
 Faculty of Chemistry, Lomonosov Moscow State University, Moscow 119991, Russia; [email protected] (N.E.B.); [email protected] (A.V.I.) 
First page
1171
Publication year
2023
Publication date
2023
Publisher
MDPI AG
e-ISSN
23046732
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
2882601440
Copyright
© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.