The Role of π-f Orbital Interactions in Eu(III) Complexes for an Effective Molecular Luminescent Thermometer

Yuichi Kitagawa; Marina Kumagai; Takayuki Nakanishi; Koji Fushimi; Yasuchika Hasegawa

doi:10.1021/acs.inorgchem.9b03492

The Role of π-f Orbital Interactions in Eu(III) Complexes for an Effective Molecular Luminescent Thermometer

Inorg Chem. 2020 May 4;59(9):5865-5871. doi: 10.1021/acs.inorgchem.9b03492. Epub 2020 Mar 6.

Authors

Yuichi Kitagawa^{1

2}, Marina Kumagai³, Takayuki Nakanishi⁴, Koji Fushimi¹, Yasuchika Hasegawa^{1

2}

Affiliations

¹ Faculty of Engineering, Hokkaido University, Kita-13, Nishi-8, Kita-ku, Sapporo, Hokkaido 060-8628, Japan.
² Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Kita-21, Nishi-10, Kita-ku, Sapporo, Hokkaido 001-0021, Japan.
³ Graduate School of Chemical Sciences and Engineering, Kita-13 Jo, Nishi-8, Kita-ku, Sapporo, Hokkaido 060-8628, Japan.
⁴ National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan.

PMID: 32142262
DOI: 10.1021/acs.inorgchem.9b03492

Abstract

Luminescent Eu(III) complexes with a ligand-to-metal charge transfer (LMCT) state were demonstrated for the development of a molecular thermometer. The Eu(III) complex was composed of three anionic ligands (hfa: hexafluoroacetylacetonate) and a phosphine oxide derivative containing a chrysene framework (diphenylphosphorylchrysene (DPCO)). The chrysene framework induced a rigid coordination structure via intermolecular interactions, resulting in a high thermal stability (decomposition point: 280 °C). The Eu(III) complex also exhibited an extremely high molar absorption coefficient (490000 cm^-1 M^-1), high intrinsic emission quantum yields (73%), and temperature-dependent energy migration between ligands and Eu(III) ion. The characteristic energy migration system was explained by the presence of the LMCT state based on π-f orbital interactions.