The role of an LMCT state on luminescence quenching in dimeric lanthanide dipivaloylmethanate compounds
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A series of four dimeric lanthanide dipivaloylmethanate (dpm) compounds with bis(diphenylphosphine)
ethane oxide (dppeO2) as an ancillary ligand having the formula [Ln2(dpm)6(dppeO2)] (Ln3+: Sm3+, Eu3+,
Gd3+, and Tb3+) have successfully been synthesized. Single-crystal X-ray diffraction analysis shows that
dimeric compounds crystallize in the P1¯ space group. Furthermore, the first coordination sphere {LnO7} of
each Ln3+ ion can be described as a capped octahedron with a distorted C3v symmetry site.
Photoluminescence data show that the Tb3+ compound exhibits high emission intensity consistent with
an efficient intramolecular energy transfer from the dpm organic ligand to the metal ion. However, the
analogous Eu3+ and Sm3+ compounds display only weak emission intensities under excitation upon the
ligand S0 → S1 transition, reflecting efficient luminescence quenching via a low-energy ligand-to-metal
charge transfer (LMCT) state and metal-to-ligand energy back transfer, respectively. For the
[Eu2(dpm)6(dppeO2)] compound, the photophysical properties based on the radiative rate (Arad), the nonradiative
rate (Anrad), and the Judd–Ofelt intensity parameters (Ω2,4) were also investigated. Besides,
theoretical studies were performed in the DFT and TD-DFT levels in conjunction with the JoySpectra platform,
yielding a deeper understanding of the intramolecular energy transfer processes. The highest value
of the energy transfer rate (W) assigned to the S1 → LMCT deactivation pathway compared to the rate
values from the 5D0 or 5D1 → LMCT channels agrees well with the experimental values of the intrinsic
(QEu
Eu) and extrinsic (QL
Eu) quantum yields. These optical results indicated that the LMCT state plays the
most critical role in Eu–dpm luminescence quenching by depopulating the excited S1 ligand state.
Como referenciar
SANTOS, PAULO R.S.; JESUS, ASHELY A.S.S.; LIMA, WILLIAM B.; SILVA, IRAN F.; ARRUDA, JOALDO G.; FAUSTINO, WAGNER M.; FELINTO, MARIA C.F.C.; BRITO, HERMI F.; COSTA, ISRAEL F.; DINIZ, RENATA; TEOTONIO, ERCULES E.S. The role of an LMCT state on luminescence quenching in dimeric lanthanide dipivaloylmethanate compounds. Dalton Transactions, v. 54, n. 24, p. 9517-9529, 2025. DOI: 10.1039/d5dt00203f. Disponível em: https://repositorio.ipen.br/handle/123456789/49361. Acesso em: 24 Mar 2026.
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