Vibronic Coupling Analysis of the Ligand-Centered Phosphorescence of Gas-Phase Gd(III) and Lu(III) 9-Oxophenalen-1-one Complexes

Abstract

The gas-phase laser-induced photoluminescence of cationic mononuclear gadolinium and lutetium complexes involving two 9-oxophenalen-1-one ligands is reported. Performing measurements at a temperature of 83 K enables us to resolve vibronic transitions. Via comparison to Franck-Condon computations, the main vibrational contributions to the ligand-centered phosphorescence are determined to involve rocking, wagging, and stretching of the 9-oxophenalen-1-one-lanthanoid coordination in the low-energy range, intraligand bending, and stretching in the medium- to high-energy range, rocking of the carbonyl and methine groups, and C-H stretching beyond. Whereas Franck-Condon calculations based on density-functional harmonic frequency computations reproduce the main features of the vibrationally resolved emission spectra, the absolute transition energies as determined by density functional theory are off by several thousand wavenumbers. This discrepancy is found to remain at higher computational levels. The relative energy of the Gd(III) and Lu(III) emission bands is only reproduced at the coupled-cluster singles and doubles level and beyond.

Theoretical Evidence of the Singlet Predominance in the Intramolecular Energy Transfer in Ruhemann's Purple Tb(III) Complexes

“…Representative references in the literature indicate that the triplet to lanthanide (T 1 →Ln 3+ ) is the traditional process [ 1–15 ] in the intramolecular energy transfer (IET) for Ln 3+ coordination compounds. However, in general, the literature ignores the singlet to lanthanide (S 1 →Ln 3+ ) IET possibility, restricting the role of S 1 state to absorb from the ground state (S 0 →S 1 ) and to populate the T 1 state via intersystem crossing (ISC) process.…”

A litmus test for the balanced description of dispersion interactions and coordination chemistry of lanthanoids

“…29 Some years ago, some of us worked on the characterization of Eu(III) complexes with different numbers of the 9-hydroxyphenalen-1-one (HPNL) ligand. [30][31][32][33][34] This ligand was chosen for its high absorption cross section, its long-lived phosphorescence, and its ability to coordinate and transfer energy to Eu atoms. [35][36][37] In these studies, the structures of the complexes were always theoretically predicted making use of DFT by using the BP86 38 functional in combination with the def2-SVP 39,40 and def2-TZVPP 39,40 basis sets.…”

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