Theoretical Study of the Structure and Bonding in ThC₂ and UC₂

The electronic structure and various molecular properties of the actinide (An) dicarbides ThC₂ and UC₂ were investigated by relativistic quantum chemical calculations. We probe five possible geometrical arrangements: two triangular structures including an acetylide (C₂) moiety, as well as the linear AnCC, CAnC, and bent CAnC geometries. Our calculations at various levels of theory indicate that the triangular species are energetically more favorable, while the latter three arrangements proved to be higher-energy structures. Our SO-CASPT2 calculations give the ground-state molecular geometry for both ThC₂ and UC₂ as the symmetric (<i>C</i>_2<i>v</i>) triangular structure. The similar and, also very close in energy, asymmetric (<i>C</i>_<i>s</i>) triangular geometry belongs to a different electronic state. DFT and single-determinant ab initio methods failed to distinguish between these two similar electronic states demonstrating the power of multiconfiguration ab initio methods to deal with such subtle and delicate problems. We report detailed data on the electronic structure and bonding properties of the most relevant structures

Profiling Sulfur(VI) Fluorides as Reactive Functionalities for Chemical Biology Tools and Expansion of the Ligandable Proteome

Here, we report a comprehensive profiling of sulfur(VI) fluorides (SVI-Fs) as reactive groups for chemical biology applications. SVI-Fs are reactive functionalities that modify lysine, tyrosine, histidine, and serine sidechains. A panel of SVI-Fs were studied with respect to hydrolytic stability and reactivity with nucleophilic amino acid sidechains. The use of SVI-Fs to covalently modify carbonic anhydrase II (CAII) and a range of kinases was then investigated. Finally, the SVI-F panel was used in live cell chemoproteomic workflows, identifying novel protein targets based on the type of SVI-F used. This work highlights how SVI-F reactivity can be used as a tool to expand the liganded proteome