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Theoretical Method for an Accurate Elucidation of Energy Transfer Pathways in Europium(III) Complexes with Dipyridophenazine (dppz) Ligand: One More Step in the Study of the Molecular Antenna Effect
journal contribution
posted on 2017-07-10, 18:09 authored by María J. Beltrán-Leiva, Plinio Cantero-López, César Zúñiga, Ana Bulhões-Figueira, Dayán Páez-Hernández, Ramiro Arratia-PérezA theoretical protocol to study the
sensitization and emission mechanism in lanthanide compounds on the
basis of multireference CASSCF/PT2 calculations is proposed and applied
to [Eu(NO3)3(dppz-CN)] and [Eu(NO3)3(dppz-NO2)] compounds synthesized and characterized
herein. The method consists of a fragmentation scheme where both the
ligand and the lanthanide fragments were calculated separately but
at the same level of theory, using ab initio wave-function-based methods
which are adequate for the treatment of quasi-degenerate states. This
is based on the fact that the absorption is ligand-localized and the
emission is europium-centered. This characteristic allowed us to describe
the most probable energy transfer pathways that take place in the
complexes, which involved an ISC between the S1 to T1 ligand states, energy transfer to 5D2 in the lanthanide fragment, and further 5D0 → 7FJ emission. For both compounds,
the triplet and 5D2 states were determined at
the CASPT2 level to be around ∼26000 and ∼22400 cm–1, respectively. This difference is in the optimal
range for the energy transfer process. Finally, the emissive state 5D0 was found at ∼18000 cm–1 and the emission bands in the range 550–700 nm, in quite
good agreement with the experimental results.
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energy transfer pathways5 D 2emissive state 5 D 0CASSCFfragmentation schemeemission mechanismAccurate Elucidationemission bandscmISCenergy transfer processab initio wave-function-based methodsquasi-degenerate stateslanthanide fragmentsCASPT 2 levelMolecular Antenna Effect5 D 2 stateslanthanide fragmentT 1 ligand stateslanthanide compoundsenergy transferS 1Energy Transfer PathwaysEuTheoretical Method
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