Unusual Actinyl Complexes with a Redox-Active N,S-Donor Ligand

Abstract

Understanding the fundamental chemistry of soft N,S-donor ligands with actinides across the series is critical for separation science toward sustainable nuclear energy. This task is particularly challenging when the ligands are redox active. We herein report a series of actinyl complexes with a N,S-donor redox-active ligand that stabilizes different oxidation states across the actinide series. These complexes are isolated and characterized in the gas phase, along with high-level electronic structure studies. The redox-active N,S-donor ligand in the products, C5H4NS, acts as a monoanion in [UVIO2(C5H4NS–)]+ but as a neutral radical with unpaired electrons localized on the sulfur atom in [NpVO2(C5H4NS•)]+ and [PuVO2(C5H4NS•)]+, resulting in different oxidation states for uranium and transuranic elements. This is rationalized by considering the relative energy levels of actinyl­(VI) 5f orbitals and S 3p lone pair orbitals of the C5H4NS– ligand and the cooperativity between An–N and An–S bonds that provides additional stability for the transuranic elements.

Semiconductive Behavior and Photoconductivity of Uranyl Dithiophosphinate Single Crystal

“…To the best of our knowledge, only one example involving the uranyl–persulfide–uranyl conformation that extends the ultraviolet absorption of a hexavalent uranyl compound to approximately 600 nm has been reported . However, investigations into the regulation of the electronic structure and bonding properties of uranyl compounds containing equatorially coordinated sulfur atoms are still limited, and there is currently no systematic exploration of the correlation between metal–ligand bonding and related functions …”

“…Figures c and S5 show the electronic structure of U-DPDPP. The four low-lying empty orbitals, i.e., the lowest unoccupied molecular orbital (LUMO) to LUMO+3, are pure U(5f) atomic orbitals, which is consistent with other types of uranyl complexes . The occupied orbitals from the highest occupied molecular orbital (HOMO) to the HOMO–6 are dominated by S(3p) electrons.…”

“…21 However, investigations into the regulation of the electronic structure and bonding properties of uranyl compounds containing equatorially coordinated sulfur atoms are still limited, and there is currently no systematic exploration of the correlation between metal−ligand bonding and related functions. 22 In this study, we report the synthesis and characterization of the uranyl dithiophosphinate single crystal UO 2 [S 2 P-(C 6 H 5 ) 2 ] 2 (CH 3 OH)•CH 3 OH (denoted U-DPDPP). U-DPDPP revealed the formation of bonds between uranyl ions and soft sulfur atom-containing ligands, highlighting an exceptionally rare electron transition property.…”

“…The four lowlying empty orbitals, i.e., the lowest unoccupied molecular orbital (LUMO) to LUMO+3, are pure U(5f) atomic orbitals, which is consistent with other types of uranyl complexes. 22 The occupied orbitals from the highest occupied molecular orbital (HOMO) to the HOMO−6 are dominated by S(3p) electrons. HOMO to HOMO−3 show S(3pz) lone pair electron characteristics, and HOMO−4 to HOMO−6 exhibit S(3px/3py)−U(5f) coordination covalent characteristics.…”