Revealing the Role of Ancillary Ligands in Modulating Bonding, Redox Properties, and Electronic Absorption Spectra of...

Mixed-ligand metallocene complexes serve as crucial precursors in organometallic actinide chemistry. However, a systematic and comprehensive understanding of how ligands influence the electronic structures and physicochemical properties of these compounds remains scarce. Hence, relativistic density functional theory (DFT) and ab initio wave function theory (WFT) calculations were carried out to elucidate the impact of auxiliary ligands on the bonding, redox properties, and electronic absorption spectra of uranium(IV) metallocene complexes, Cp*₂U(NR₂)X (Cp* = C₅Me₅, R = SiMe₃, and X = F, Cl, Br, I, NCO, and OEt). The calculated redox potentials display high agreement with the available experimental values, with absolute deviations less than 0.26 V. Additionally, the simulated electronic absorption spectra show close alignment with the available experimental results, enabling the precise identification of the two primary absorption regions in the experimental spectra. This study further reveals strong linear correlations (R² > 0.97) between ligand field parameters and the computed reduction potentials, orbital interactions, and electronic transition energies. These correlations underscore the pivotal role of ligand electron-donating or electron-withdrawing abilities in modulating the electronic structures of tetravalent uranium complexes. These findings provide a solid theoretical foundation for guiding experimental efforts to tailor the properties of organoactinide compounds via strategic ligand modification.