How the Ancillary Ligand X Drives the Redox Properties of Biscyclopentadienyl Pentavalent Uranium Cp₂U(═N–Ar)X Complexes

Relativistic zero order regular approximation (ZORA) density functional theory computations, coupled with the conductor-like screening model for solvation effects, are used to investigate redox properties of a series biscyclopentadienyl pentavalent uranium(V) complexes Cp2U(═N–Ar)X (Ar = 2,6-Me2-C6H3; X OTf, C6F5, SPh, C═CPh, NPh2, Ph, Me, OPh, N(TMS)2, N═CPh2). Regarding UV/UIV and UVI/UV couple systems, linear correlation (R2 ∼ 0.99) is obtained at ZORA/BP86/TZP level, between calculated ionization energies measured experimental E1/2 half-wave oxidation potentials (UVI/UV) electron affinities reduction (UV/UIV). The study brings light importance effects that needed in achieve good agreement experiment. Introducing spin–orbit coupling corrections slightly improves this agreement. Both singly occupied molecular orbital lowest unoccupied neutral UV exhibit majority 5f character. frontier orbitals show substantial ancillary ligand σ and/or π character drives properties. Moreover, our investigations allow estimating N(TMS)2 which no electrochemical data exist.