Photodissociation and Infrared Spectroscopy of Uranium-Nitrogen Cation Complexes

Pentacoordinated pyramidal structures and bonding properties of WN10-/0: anion photoelectron spectroscopy and theoretical calculations

Anion photoelectron spectroscopy and theoretical calculations were used to investigate the structural and bonding properties of WN10-/0. The electron affinity of WN10 is measured to be 1.582 ± 0.030 eV. The frequency of the NN stretch in WN10 is measured to be 2170 ± 80 cm-1, which is red-shifted with respect to that of the dinitrogen molecule indicating that the NN bonds are weakened in WN10. The theoretical adiabatic detachment energy (ADE) and vertical detachment energy (VDE) of WN10- obtained by calculations at the CCSD(T)/CBS level agree well with experimental results. The structures of WN10-/0 are C4v symmetric pentacoordinated pyramidal structures with five end-on dinitrogen ligands. Our experiments show that the peak of WN10- is dominant in the mass spectrum of anionic WNn, whereas the mass peak of WN12+ is dominant in the mass spectrum of cationic WNn, implying that the stabilities of WNn clusters are strongly related to their charge states.

Conversion of a UO22+ Precursor to UH+ and U+ Using Tandem Mass Spectrometry to Remove Both "yl" Oxo Ligands

Multiple-stage collision-induced dissociation (CID) of a uranyl propiolate cation, [UO2(O2C-C≡CH)]+, can be used to prepare the U-methylidyne species [O═U≡CH]+ [J. Am. Soc. Mass Spectrom. 2019, 30, 796-805]. Here, we report that CID of [O═U≡CH]+ causes elimination of CO to create [UH]+, followed by a loss of H• to generate U+. A feasible, multiple-step pathway for the generation of [UH]+ was identified using DFT calculations. These results provide the first demonstration that multiple-stage CID can be used to prepare both U+ and UH+ directly from a UO22+ precursor for the subsequent investigation of ion-molecule reactivity.

Cation Complexes of Uranium and Thorium with Cyclooctatetraene: Photochemistry and Decomposition Products

Ion-molecule complexes of uranium or thorium singly-charged positive ions bound to cyclooctatetraene (COT), i.e., M⁺(COT)_1,2, are produced by laser ablation and studied with UV laser photodissociation. The ions are selected by mass and excited at 355 or 532 nm, and the ionized dissociation products are detected using a reflectron time-of-flight mass spectrometer. The abundant fragments M⁺(C₆H₆), M⁺(C₄H₄), and M⁺(C₂H₂) occur for complexes of both metals, whereas the M⁺(C₄H₂), M⁺(C₃H₃), and M⁺(C₅H₅) fragments are prominent for uranium complexes but not for thorium. Additional experiments investigate the dissociation of M⁺(benzene)_1,2 ions which may be intermediates in the fragmentation of the COT ions. The experiments are complemented by computational quantum chemistry to investigate the structures and energetics of fragment ions. Various cation-π and metallacycle structures are indicated for different fragment ions. The metal ion-ligand bond energies for corresponding complex ions are systematically greater for the thorium species. The computed thermochemistry makes it possible to explain the mechanistic details of the photochemical fragmentation processes and to reveal new actinide organometallic structures.