A combined experimental-molecular modeling study of crown ether europium complexes: Effects of the coordinated anion on structural and luminescence properties

Alex Sandro N da Silva Filho; Jéssica I R de Souza; Ana Carolina Roma; Juliana A B da Silva; Ricardo L Longo; S Alves Jr; Mônica F Belian

doi:10.1016/j.saa.2023.123704

A combined experimental-molecular modeling study of crown ether europium complexes: Effects of the coordinated anion on structural and luminescence properties

Spectrochim Acta A Mol Biomol Spectrosc. 2024 Mar 5:308:123704. doi: 10.1016/j.saa.2023.123704. Epub 2023 Dec 2.

Authors

Alex Sandro N da Silva Filho¹, Jéssica I R de Souza², Ana Carolina Roma³, Juliana A B da Silva⁴, Ricardo L Longo⁵, S Alves Jr⁵, Mônica F Belian⁶

Affiliations

¹ Programa de Pós-Graduação em Química, Universidade Federal Rural de Pernambuco, Recife, PE 52171-900, Brazil.
² Programa de Pós-Graduação em Ciência de Materiais, Universidade Federal de Pernambuco, 50670-901 Recife, PE, Brazil.
³ Departamento de Química Fundamental, Universidade Federal de Pernambuco, 50670-901, Recife, Pernambuco, Brazil.
⁴ Programa de Pós-Graduação em Química, Universidade Federal Rural de Pernambuco, Recife, PE 52171-900, Brazil; Núcleo Interdisciplinar de Ciências Exatas e da Natureza, CAA, Universidade Federal de Pernambuco, Nova Caruaru, Caruaru, PE 55.014-900, Brazil.
⁵ Programa de Pós-Graduação em Ciência de Materiais, Universidade Federal de Pernambuco, 50670-901 Recife, PE, Brazil; Departamento de Química Fundamental, Universidade Federal de Pernambuco, 50670-901, Recife, Pernambuco, Brazil.
⁶ Programa de Pós-Graduação em Química, Universidade Federal Rural de Pernambuco, Recife, PE 52171-900, Brazil; Departamento de Química, Universidade Federal Rural de Pernambuco, 52171-900 Recife, Pernambuco, Brazil. Electronic address: monica.freirebelian@ufrpe.br.

PMID: 38070311
DOI: 10.1016/j.saa.2023.123704

Abstract

It is reported the synthesis, characterization by elemental analysis, thermogravimetry; electronic absorption, infrared, excitation, and emission spectroscopies of the [Eu(12C4)(phen)₂(X)_n]X₂ complexes, where 12C4 = 12-crown-4, phen = 1,10-phenanthroline, and X = F^-, Cl^-, Br^-, SCN^-, ClO₄^-, and NO₃^-. It is verified that the polarizability of the anion X^- exerts remarkable effects on the emission process. As a general trend, lower wavenumbers for the ⁷F₀→⁵L₆, ⁷F₀→⁵D₂ and ⁷F₀→⁵D₁ transitions are associated with the anions with higher volumes and, consequently, higher polarizability. The molecular modeling results performed with quantum methods (RHF and DFT) suggest some relationships between the calculated structures, electronic, and luminescence properties with the presence of the LMCT (ligand-to-metal charge transfer) states, which explains the differences in the emission spectra of these complexes due to the coordinated anion.

Keywords: Anion effect; Computational modeling; Crown ether; DFT; Lanthanide; Luminescence.