Prediction of pressure-induced redshift of f1→d(t2g)1 excitations in Cs2NaYCl6:Ce3+ and its connection with bond-length shortening

Cerium Photocatalyst in Action: Structural Dynamics in the Presence of Substrate Visualized via Time-Resolved X-ray Liquidography

[Ce(III)Cl6]3-, with its earth-abundant metal element, is a promising photocatalyst facilitating carbon-halogen bond activation. Still, the structure of the reaction intermediate has yet to be explored. Here, we applied time-resolved X-ray liquidography (TRXL), which allows for direct observation of the structural details of reaction intermediates, to investigate the photocatalytic reaction of [Ce(III)Cl6]3-. Structural analysis of the TRXL data revealed that the excited state of [Ce(III)Cl6]3- has Ce-Cl bonds that are shorter than those of the ground state and that the Ce-Cl bond further contracts upon oxidation. In addition, this study represents the first application of TRXL to both photocatalyst-only and photocatalyst-and-substrate samples, providing insights into the substrate's influence on the photocatalyst's reaction dynamics. This study demonstrates the capability of TRXL in elucidating the reaction dynamics of photocatalysts under various conditions and highlights the importance of experimental determination of the structures of reaction intermediates to advance our understanding of photocatalytic mechanisms.

Toward Opto-Structural Correlation to Investigate Luminescence Thermometry in an Organometallic Eu(II) Complex

Lanthanide-based luminescent materials have unique properties and are well-studied for many potential applications. In particular, the characteristic 5d → 4f emission of divalent lanthanide ions such as Eu^II allows for tunability of the emissive properties via modulation of the coordination environment. We report the synthesis and photoluminescence investigation of pentamethylcyclopentadienyleuropium(II) tetrahydroborate bis(tetrahydrofuran) dimer (1), the first example of an organometallic, discrete molecular Eu^II band-shift luminescence thermometer. Complex 1 exhibits an absolute sensitivity of 8.2 cm^-1 K^-1 at 320 K, the highest thus far observed for a lanthanide-based band-shift thermometer. Opto-structural correlation via variable-temperature single-crystal X-ray diffraction and fluorescence spectroscopy allows rationalization of the remarkable thermometric luminescence of complex 1 and reveals the significant potential of molecular Eu^II compounds in luminescence thermometry.

Insights into the complexity of the excited states of Eu-doped luminescent materials

Multiconfigurational ab initio embedded-cluster methods give a detailed view of the excited states of Eu-doped luminescent materials, improving the understanding of their structure and how it is affected by changing the host's chemical composition.

Detailed interpretation of the 5f-6d absorption spectrum of U3+ in Cs2NaYCl6 and high pressure effects based on an ab initio simulation

The 5f-->6d(t(2g)) absorption spectrum of U(3+)-doped Cs(2)NaYCl(6) is simulated with a quantum chemical ab initio embedded-cluster approach applied to U(3+) substitutional defects of O(h) local symmetry. The first-principles results help to provide a detailed interpretation of the very rich experimental absorption spectrum of this material between 14 000 and 25 000 cm(-1). Also, the effects of high pressures up to 26 kbars on the absorption spectrum are predicted, the most relevant feature being a redshift of around 21 cm(-1)/kbar, which is the fingerprint of a bond length shortening upon 5f-->6d(t(2g)) excitation.

Quantum chemical study of 4f→5d excitations of trivalent lanthanide ions doped in the cubic elpasolite Cs2NaYCl6. Ce3+ to Tb3+

Wave-function-based ab initio calculations on the lowest states of the 4f(n),4f(n-1)5d(t2g)1, and 4f(n-1)5d(e(g))1 configurations of (LnCl6)3- clusters (Ln=Ce to Tb) embedded in the cubic elpasolite Cs2NaYCl6 have been performed, in an attempt to contribute to a comprehensive understanding of the 4f-->5d excitations of lanthanide ions in crystals. Reliable data are provided on the changes of bond lengths and breathing mode vibrational frequencies upon 4f-->5d(t2g) and 4f-->5d(e(g)) excitations, as well as on minimum-to-minimum and vertical absorption and emission transitions, and on the Stokes shifts. The available experimental data are discussed and predictions are made. The stabilization of the 4f-->5d(baricenter) excitation of the doped ions with respect to the 4f-->5d excitations of the free ions, which is a key variable for the understanding of these excitations in solid hosts, is analyzed and found to be due, in two-thirds, to dynamic ligand correlation effects and, in one-third, to orbital relaxation, charge transfer, and covalency effects present in a mean-field approximation.