Luminescent Properties of Europium and Terbium Phthalate Complexes in Water- N , N' -dimethylformamide Mixed Solvents

Artur M. Shevalev; Bryan Vargas; Oleg S. Butorlin; Nikita A. Bogachev; Andrey Mereshchenko

doi:10.22146/ijc.119964

Luminescent Properties of Europium and Terbium Phthalate Complexes in Water-N,N'-dimethylformamide Mixed Solvents

https://doi.org/10.22146/ijc.119964

Artur M. Shevalev⁽¹⁾, Bryan Vargas⁽²⁾, Oleg S. Butorlin⁽³⁾, Nikita A. Bogachev⁽⁴⁾, Andrey Mereshchenko^(5*)

(1) Institute of Chemistry, Saint-Petersburg State University, 7/9 Universitetskaya Emb., St. Petersburg 199034, Russia
(2) School of Chemical Sciences and Engineering, Yachay Tech University, Hacienda San José s/n y Proyecto Yachay, San Miguel de Urcuquí 100115, Ecuador
(3) Institute of Chemistry, Saint-Petersburg State University, 7/9 Universitetskaya Emb., St. Petersburg 199034, Russia
(4) Institute of Chemistry, Saint-Petersburg State University, 7/9 Universitetskaya Emb., St. Petersburg 199034, Russia
(5) School of Physical Sciences and Nanotechnology, Yachay Tech University, Hacienda San José s/n y Proyecto Yachay, San Miguel de Urcuquí 100115, Ecuador
(*) Corresponding Author

Abstract

The photoluminescent behavior of europium(III) and terbium(III) phthalate complexes was studied in mixed water and N,N'-dimethylformamide (DMF) media at a fixed lanthanide-to-ligand molar ratio of 1:2. The emission spectra contained the characteristic narrow transition bands of Tb³⁺ and Eu³⁺. Excitation spectra revealed broad ultraviolet absorption bands associated with the phthalate ligand, indicating efficient ligand-to-metal energy transfer. For both lanthanides, the photoluminescence intensity increases steadily with increasing DMF content, while the normalized emission and excitation spectra remain essentially unchanged, indicating that the dominant coordination framework is preserved across the solvent range. The intensity increase is mainly due to suppression of non-radiative quenching upon partial replacement of coordinated water by DMF, since O–H vibrations of inner-sphere water efficiently deactivate the long-lived ⁵D₀ and ⁵D₄ excited states of Eu³⁺ and Tb³⁺, respectively. At the same time, the rise in asymmetry ratio and in the calculated Eu³⁺ radiative decay rate with increasing DMF fraction suggests that DMF coordination lowers the local symmetry around the lanthanide ions and moderately enhances the radiative probability of f–f transitions. These findings demonstrate that solvent composition provides an effective strategy for tuning the optical response of lanthanide coordination systems.

Keywords

europium; terbium; lanthanide; luminescence; antenna effect; solvent effects

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DOI: https://doi.org/10.22146/ijc.119964