Does the bending of uranyl influence its spectroscopy and luminescence

Abstract

Bent uranyl complexes can be formed with chloride ligands and 1,10-phenanthroline (phen) ligands bound to the equatorial and axial planes of the uranyl(VI) moiety, as revealed by the crystal structures, IR and Raman spectroscopy and quantum chemical calculations. With the goal of probing the influence of chloride and phenanthroline coordination enforcing the bending on the absorption and emission spectra of this complex, spin-orbit time-dependent density functional theory calculations for the bare uranyl complexes as well as for the free UO2Cl2 subunit and the UO2Cl2(phen)2 ligand we performed. The emission spectra has been fully simulated by ab initio methods and compared to experimental photoluminescence spectra, recorded for the first time for UO2Cl2(phen)2. Notably, the bending of uranyl in UO2Cl2 and UO2Cl2(phen)2 triggers vibronically induced excitations of the uranyl bending mode, yielding a denser spectrum.

How Does Bending the Uranyl Unit Influence Its Spectroscopy and Luminescence?

“…A preprint version of this work was deposited at ChemRxiv. 77 The authors declare no competing financial interest.…”

Core Excitations of Uranyl in Cs2UO2Cl4 from Relativistic Embedded Damped Response Time-Dependent Density Functional Theory Calculations

“…Relaxation aside, the comparable performance of CAM-B3LYP with respect to RASSCF/RASPT2 is in line with previous benchmark studies 131,132 and has been explained in terms of its good ability to minimize self-interaction errors that plague other functionals, so that excitation energies can be reliably obtained with it, including for charge-transfer excitations. 96,133 Taken as a whole, we attribute the overestimation of peak splittings shown for all of these calculations to the lack of equatorial ligands, since when these are included (embedding or supermolecular 4c-DR calculations), we achieve very good agreement with the experiment, especially for the T6−T4 and T6−T5 splittings. It is interesting to note that the RASPT2 approach, which one could expect to improve upon RASSCF, ends up further overestimating peak splittings.…”

Systematic Study of Solid-State U(VI) Photoreactivity: Long-Lived Radicalization and Electron Transfer in Uranyl Tetrachloride

“…Notably, compounds 2, 3, and, to a lesser extent, 1 display additional vibronic features in the emission band, which correspond to coupled U−Cl vibrational modes (a phenomenon we have reported previously for other uranyl tetrachloride-containing materials). 14,48,49 There are notable differences in the excitation profiles across 1−3 (Figure 4, right), namely, the excitation bands vary in relative intensities as the identity of the viologen changes. For example, in 1, the axial and equatorial excitation bands are similar in intensity, whereas for 3, the equatorial excitation band is much higher in intensity than the axial band.…”