Impact of ligand-centered excited states on luminescence sensitization in Pr3+ complexes with β-diketones

V M Korshunov; M T Metlin; S A Ambrozevich; I S Golovanov; V E Gontcharenko; A S Selyukov; I V Taydakov

doi:10.1016/j.saa.2021.119863

Impact of ligand-centered excited states on luminescence sensitization in Pr³⁺ complexes with β-diketones

Spectrochim Acta A Mol Biomol Spectrosc. 2021 Nov 5:260:119863. doi: 10.1016/j.saa.2021.119863. Epub 2021 Apr 29.

Authors

V M Korshunov¹, M T Metlin², S A Ambrozevich³, I S Golovanov⁴, V E Gontcharenko⁵, A S Selyukov³, I V Taydakov⁶

Affiliations

¹ P.N.Lebedev Physical Institute of the Russian Academy of Sciences, 53 Leninsky Prospect, 119991 Moscow, Russia; Bauman Moscow State Technical University, 5/1 2-ya Baumanskaya Str., 105005 Moscow, Russia. Electronic address: korshunovvm@lebedev.ru.
² P.N.Lebedev Physical Institute of the Russian Academy of Sciences, 53 Leninsky Prospect, 119991 Moscow, Russia; Bauman Moscow State Technical University, 5/1 2-ya Baumanskaya Str., 105005 Moscow, Russia.
³ P.N.Lebedev Physical Institute of the Russian Academy of Sciences, 53 Leninsky Prospect, 119991 Moscow, Russia.
⁴ N.D.Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky Prospect, 119991 Moscow, Russia.
⁵ Moscow State University, 119991 Moscow, Russia.
⁶ P.N.Lebedev Physical Institute of the Russian Academy of Sciences, 53 Leninsky Prospect, 119991 Moscow, Russia; Plekhanov Russian University of Economics, Stremyanny lane, 36, 117997 Moscow, Russia. Electronic address: taidakov@gmail.com.

PMID: 34030034
DOI: 10.1016/j.saa.2021.119863

Abstract

In this study, two novel Pr³⁺ complexes with different 1,3-diketonate ligands were synthesized and investigated. To study the effect of the ancillary ligand on the energy transfer mechanisms in the complexes, a phenanthroline ligand was introduced. To take into account the influence of the ligand environment composed of different ligands on the energy transfer and relaxation processes, we compared the synthesized compounds with a similar complex containing the phenanthroline ligand. The spectroscopic studies in the visible and near-infrared spectral regions were supplemented with DFT and TD-DFT calculations. We found two ligand-to-ligand charge transfer (LLCT) states, with one state corresponding to energy transfer between 1,3-diketones and the other - to energy transfer from the 1,3-diketone to the phenanthroline motif. It was demonstrated that optical excitation via the latter channel leads to a fourfold increase in the luminescence quantum yield as compared with excitation via the π-π^∗ transitions in 1,3-diketones. Moreover, both LLCT states provide sensitization of the Pr³⁺ luminescence involving the ³P₀ and ³P₁ levels.

Keywords: 1,10-phenanthroline; 1,3-diketones; Luminescence; Near-infrared emission; Pr(III) complexes; Pyrazole.