Optical properties and electronic structure of Eu(III) complexes with HMPA and TPPO

A V Shurygin; V I Vovna; V V Korochentsev; A G Mirochnik; I V Kalinovskaya; V I Sergienko

doi:10.1016/j.saa.2020.119397

Optical properties and electronic structure of Eu(III) complexes with HMPA and TPPO

Spectrochim Acta A Mol Biomol Spectrosc. 2021 Apr 5:250:119397. doi: 10.1016/j.saa.2020.119397. Epub 2020 Dec 30.

Authors

A V Shurygin¹, V I Vovna², V V Korochentsev¹, A G Mirochnik³, I V Kalinovskaya³, V I Sergienko⁴

Affiliations

¹ Far Eastern Federal University, 8 Sukhanova St., Vladivostok, Russia.
² Far Eastern Federal University, 8 Sukhanova St., Vladivostok, Russia. Electronic address: shurygin.av@dvfu.ru.
³ Institute of Chemistry, FEB RAS, 159 Prosp. 100-letiya Vladivostoka, Vladivostok, Russia.
⁴ Far Eastern Branch, RAS, 50 Svetlanskaya St., Vladivostok, Russia.

PMID: 33422875
DOI: 10.1016/j.saa.2020.119397

Abstract

Two adducts of Eu(III) tris-hexofluoroacetylacetonate with HMPA (OP(N(CH₃)₂)₃, hexamethylphosphotriamide) and TPPO (OP(C₆H₅)₃, triphenylphosphine oxide) were studied by optical spectroscopy and quantum chemistry (DFT/TD-DFT). The structure of the higher occupied molecular orbitals (MO) of the two adducts determines differences in the position of the excitation band maximum of hfac ligands. According to the calculation data, all excited states are caused by the transition to 3 vacant π₄* MOs of hfac ligands. Optical spectra of absorption, excitation and luminescence are obtained and interpreted. The peculiarity of the HOMO-LUMO structure, the low value of the energy gap, and the broadened absorption region of hfac ligands compensate the low absorbance ability of the groups N(CH₃)₂ in a region of 220-360 nm for the adduct Eu(hfac)₃(HMPA)₂, reducing the luminescence intensity by only 5-10% relative to the adduct of the Eu(III) complex with TPPO ligands.

Keywords: DFT; Electronic structure; Eu(III); HMPA; Luminescence; Optical spectroscopy; TD-DFT; TPPO; β-Diketonates adducts.