A Hexagonal Bipyramidal Uranyl(V) Single-Ion Magnet Showing Finger-Type Photoluminescence

Pei-Yu Liao; Hao-Ran Xing; Yi-Ling Zhong; Xi-Nan Xu; Peng-Xu Lu; Shang-Da Jiang; Cheng-Hui Li; Jun-Liang Liu; Richard A Layfield; Ming-Liang Tong

doi:10.1021/jacs.5c04541

A Hexagonal Bipyramidal Uranyl(V) Single-Ion Magnet Showing Finger-Type Photoluminescence

J Am Chem Soc. 2025 Jun 16. doi: 10.1021/jacs.5c04541. Online ahead of print.

Authors

Affiliations

¹ Key Laboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education, School of Chemistry, IGCME, GBRCE for Functional Molecular Engineering, Sun Yat-Sen University, Guangzhou 510006, P. R. China.
² State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing National Laboratory of Microstructures, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210023, P. RChina.
³ Spin-X Institute, School of Chemistry and Chemical Engineering, State Key Laboratory of Luminescent Materials and Devices, Guangdong-Hong Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional Materials, South China University of Technology, Guangzhou 510640, P. R. China.
⁴ Department of Chemistry, School of Life Science, University of Sussex, Brighton, Falmer BN1 9QR, United Kingdom.

PMID: 40524341
DOI: 10.1021/jacs.5c04541

Abstract

The occurrence of uranyl(V) compounds in nuclear fuel cycles and radioactive waste necessitates a deep understanding of the electronic structure of these 5f¹ species. Characteristic properties of pentavalent uranium can include single-molecule magnet (SMM) behavior and finger-like luminescence. However, both properties have not previously been observed in the same uranyl(V) complex. Here, we show that one-electron reduction of the hexagonal bipyramidal uranyl(VI) compound [UO₂(L^N6)][BPh₄]₂ (1-U) gives the uranyl(V) congener [UO₂(L^N6)][BPh₄] (2-U) (L^N6 is a hexadentate N-donor with two connected bis(imino)pyridine groups). In addition to field-induced slow magnetic relaxation, 2-U displays photoluminescence upon excitation at 440 nm, the first time that both phenomena are observed in one uranyl(V) complex. The emission from 2-U is characterized by five well-resolved bands in the region 510-586 nm, in contrast to the broad emission observed for 1-U centered on 650 nm. The relationship between the electronic structure of 1-U and 2-U is emphasized by the photochromic behavior of 1-U, which, upon irradiation at 365 nm, adopts a stable photoexcited state 1-U^* following a ligand-to-metal electron transfer, with the magnetic and spectroscopic properties of 1-U^* being similar to those of 2-U. A computational study of 1-U and 2-U explains their contrasting emission profiles in terms of the uranyl oxo ligands participating in the key transitions for 2-U but not for 1-U, with the stretching vibrations of the L^N6 ligand also contributing to the fine structure.