TY - JOUR
T1 - Theoretical Method for an Accurate Elucidation of Energy Transfer Pathways in Europium(III) Complexes with Dipyridophenazine (dppz) Ligand
T2 - One More Step in the Study of the Molecular Antenna Effect
AU - Beltrán-Leiva, María J.
AU - Cantero-López, Plinio
AU - Zúñiga, César
AU - Bulhões-Figueira, Ana
AU - Páez-Hernández, Dayán
AU - Arratia-Pérez, Ramiro
N1 - Funding Information:
This work has been supported by the Grants FONDECYT Nos. 1150629 and 11140294. P.C.-L. and M.J.B.-L. acknowledge CONICYT/Doctorado Nacional 2013/63130037 and 2015/21151553 for their Ph.D. fellowships respectively. Furthermore, P.C-L. acknowledges Andr?s Bello University (internal project DI-712-15/I). The authors thank Ph.D.s Osvaldo Serra and Paulo Cesar de Sousa Filho at the Rare Earths Laboratory FFCLRP, University of S?o Paulo, for the luminescence measurements.
PY - 2017/8/7
Y1 - 2017/8/7
N2 - A 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.
AB - A 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.
UR - http://www.scopus.com/inward/record.url?scp=85027032381&partnerID=8YFLogxK
U2 - 10.1021/acs.inorgchem.7b01221
DO - 10.1021/acs.inorgchem.7b01221
M3 - Article
AN - SCOPUS:85027032381
SN - 0020-1669
VL - 56
SP - 9200
EP - 9208
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 15
ER -