Spectroscopic aspects for the Yb3+ coordination compound with a large energy gap between the ligand and Yb3+ excited states

Ewa Kasprzycka; Albano N Carneiro Neto; Viktor A Trush; Oscar L Malta; Lucjan Jerzykiewicz; Vladimir M Amirkhanov; Janina Legendziewicz; Paula Gawryszewska

doi:10.1016/j.saa.2022.121072

Spectroscopic aspects for the Yb³⁺ coordination compound with a large energy gap between the ligand and Yb³⁺ excited states

Spectrochim Acta A Mol Biomol Spectrosc. 2022 Jun 5:274:121072. doi: 10.1016/j.saa.2022.121072. Epub 2022 Feb 24.

Authors

Ewa Kasprzycka¹, Albano N Carneiro Neto², Viktor A Trush³, Oscar L Malta⁴, Lucjan Jerzykiewicz¹, Vladimir M Amirkhanov³, Janina Legendziewicz¹, Paula Gawryszewska⁵

Affiliations

¹ Faculty of Chemistry, University of Wroclaw, 14 F. Joliot-Curie Str., 50-383 Wroclaw, Poland.
² Physics Department and CICECO-Aveiro Institute of Materials, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
³ Department of Chemistry, Kyiv National Taras Shevchenko University, Volodymyrska str. 64, Kyiv 01601, Ukraine.
⁴ Departamento de Química Fundamental, Universidade Federal de Pernambuco, Cidade Universitária, 50740-560 Recife, Brazil. Electronic address: oscar.malta@ufpe.br.
⁵ Faculty of Chemistry, University of Wroclaw, 14 F. Joliot-Curie Str., 50-383 Wroclaw, Poland. Electronic address: paula.gawryszewska@chem.uni.wroc.pl.

PMID: 35248854
DOI: 10.1016/j.saa.2022.121072

Abstract

We present the experimental and theoretical results that made it possible to propose the energy transfer mechanism for a Yb complex with a large energy gap between the ligand and Yb excited states using a theoretical model and experimental data. Absorption and emission spectroscopy in the 300-4 K range is used for the study of the Yb³⁺ compound with N-phosphorylated sulfonamide (Na[YbL₄]), which, despite the large energy gap, is characterized by high emission sensitization efficiency (η_sens = 40%) and relatively long Yb³⁺ emission lifetime (27 μs). The crystal structure of Na[YbL₄], radiative lifetime (930 μs), refractive index (1.46), intrinsic (3.0%), and overall (1.3%) emission quantum yield were determined. To obtain the electronic properties of the Na[YbL₄], a time-dependent density functional theory (TD-DFT) was performed. The intramolecular energy transfer (IET) rates from the excited states S₁ and T₁ to the Yb³⁺ ion as well as between the ligand and the ligand-to-metal charge transfer (LMCT) states were calculated. Once the intersystem crossing S₁ → T₁ is not so effective due to a large energy gap between S₁ and T₁ (≈10000 cm^-1), it has been shown that the LMCT state acts as an additional channel to feed the T₁ state. Then, the T₁ can transfer energy to the Yb^{3+ 2}F_5/2 energy level (W_T), where W_T is dominated by the exchange mechanism. Based on IET and a rate equation model, the overall emission quantum yield Q^L_Ln was simulated with and without the LMCT, this also confirmed that the pathway S₁ → LMCT → T₁ → Yb³⁺ is more likely than the S₁ → T₁ → Yb³⁺ one.

Keywords: Absorption spectroscopy; Energy transfer; Luminescence; N-phosphorylated sulfonamide; Theoretical calculations; Ytterbium.