Solvent-dependent Sensitization and Photophysical Behavior of Ir^III-Eu^III Bimetallic Complexes.

Authors

Felipe S M Canisares, Vytor C Oliveira, Alessandro B S Garcia, João Honorato, Javier A Ellena, Marian R Davolos, Ana M Pires, Sergio A M Lima

Published in

Journal of fluorescence. Aug 11, 2026. Epub Aug 11, 2026.

Abstract

The photophysical properties of a heterobimetallic Ir^III-Eu^III complex were investigated in solvents with different polarity, coordinating ability, and vibrational characteristics to elucidate the factors governing Eu^III sensitization. Steady-state and time-resolved luminescence measurements revealed that the solvent profoundly influences both the donor-to-acceptor energy-transfer process and the europium-centered emission. The apparent Ir^III → Eu^III energy-transfer rate constants (k_ET) and donor-to-acceptor energy-transfer efficiencies (η_ET) were estimated from the residual ³MLCT emission lifetimes (τ_q) of the Ir^III-Eu^III complex and the corresponding Ir^III-Gd^III analog (τ_u). The results showed a general tendency toward higher energy-transfer rates and efficiencies in solvents with high polarity, coordinating ability, and free of O-H oscillators, reaching k_ET values up to 2.6 × 10⁷ s^-1 and η_ET values up to 90% in DMSO. Solvent polarity was found to indirectly modulate the energy transfer (ET) process by influencing the energies of the excited states and the donor-acceptor electronic coupling. In contrast, protic solvents strongly quenched Eu^III emission due to the presence of high-energy O-H oscillators, despite moderate ET efficiencies. Degassing experiments performed in dichloromethane and chloroform demonstrated that dissolved oxygen has only a minor effect on the η_ET efficiency. The results reveal a complex interplay between solvent polarity, coordinating ability, donor-acceptor gap, and non-radiative deactivation pathways, providing new insights into the design of efficient d-f heterobimetallic luminescent systems.

PMID:
42579262
Bibliographic data and abstract were imported from PubMed on 11 Aug 2026.

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