Molecules with large enough dipole moments can bind an electron by the dipole field, which has little effect on the molecular core. A molecular anion can be excited to a dipole-bound state, which can autodetach by vibronic coupling. Autodetachment spectroscopy of a complex anion cooled in a cryogenic ion trap is reported. Vibrational spectroscopy of the dehydrogenated uracil radical is obtained by a dipole-bound state with partial rotational resolution. Fundamental frequencies for 21 vibrational modes of the uracil radical are reported. The electron affinity of the uracil radical is measured accurately to be 3.4810±0.0006 eV and the binding energy of the dipole-bound state is measured to be 146±5 cm⁻¹. The rotational temperature of the trapped uracil anion is evaluated to be 35 K.

Chirality is vital in chemistry. Its importance in atomic clusters has been recognized since the discovery of the first chiral fullerene, the D₂ symmetric C₇₆.1 A number of gold clusters have been found to be chiral,2 raising the possibility to use them as asymmetric catalysts. The discovery of clusters with enantiomeric structures is essential to design new chiral materials with tailored chemical and physical properties.3 Herein we report the first inherently chiral boron cluster of [B₃₀]⁻ in a joint photoelectron spectroscopy and theoretical study. The most stable structure of [B₃₀]⁻ is found to be quasiplanar with a hexagonal hole. Interestingly, a pair of enantiomers arising from different positions of the hexagonal hole are found to be degenerate in our global minimum searches and both should co-exist experimentally because they have identical electronic structures and give rise to identical simulated photoelectron spectra.

Molecules with large enough dipole moments can bind an electron by the dipole field, which has little effect on the molecular core. A molecular anion can be excited to a dipole-bound state, which can autodetach by vibronic coupling. Autodetachment spectroscopy of a complex anion cooled in a cryogenic ion trap is reported. Vibrational spectroscopy of the dehydrogenated uracil radical is obtained by a dipole-bound state with partial rotational resolution. Fundamental frequencies for 21 vibrational modes of the uracil radical are reported. The electron affinity of the uracil radical is measured accurately to be 3.4810±0.0006 eV and the binding energy of the dipole-bound state is measured to be 146±5 cm⁻¹. The rotational temperature of the trapped uracil anion is evaluated to be 35 K.

It has been a long-sought goal in cluster science to discover stable atomic clusters as building blocks for cluster-assembled nanomaterials, as exemplified by the fullerenes and their subsequent bulk syntheses.1, 2 Clusters have also been considered as models to understand bulk properties, providing a bridge between molecular and solid-state chemistry.3 Because of its electron deficiency, boron is an interesting element with unusual polymorphism. While bulk boron is known to be dominated by the three-dimensional (3D) B₁₂ icosahedral motifs,4 new forms of elemental boron are continuing to be discovered.5 In contrast to the 3D cages commonly found in bulk boron, in the gas phase two-dimensional (2D) boron clusters are prevalent.6–8 The unusual planar boron clusters have been suggested as potential new bulking blocks or ligands in chemistry.6a Herein we report a joint experimental and theoretical study on the [Ta₂B₆]⁻ and [Ta₂B₆] clusters. We found that the most stable structures of both the neutral and anion are D_6h bipyramidal, similar to the recently discovered MB₆M structural motif in the Ti₇Rh₄Ir₂B₈ solid compound.9

We report a combined photoelectron spectroscopic and relativistic quantum chemistry study on gaseous UCl₅⁻ and UCl₅. The UCl₅⁻ anion is produced using electrospray ionization and found to be highly electronically stable with an adiabatic electron binding energy of 4.76±0.03 eV, which also represents the electron affinity of the neutral UCl₅ molecule. Theoretical investigations reveal that the ground state of UCl₅⁻ has an open shell with two unpaired electrons occupying two primarily U 5f and 5f_xyz based molecular orbitals. The structures of both UCl₅⁻ and UCl₅ are theoretically optimized and confirmed to have C_4v symmetry. The computational results are in good agreement with the photoelectron spectra, providing insights into the electronic structures and valence molecular orbitals of UCl₅⁻ and UCl_5. We also performed systematic theoretical studies on all the uranium pentahalide complexes UX₅⁻ (X=F, Cl, Br, I). Chemical bonding analyses indicate that the UX interactions in UX₅⁻ are dominated by ionic bonding, with increasing covalent contributions for the heavier halogen complexes.

Anion photoelectron spectroscopy and theoretical calculations are combined to probe the structures and chemical bonding of two boron-rich oxide clusters, B₅O₃⁻ and B₆O₃⁻, which are shown to be appropriately formulated as B₂(BO)₃⁻ and B₃(BO)₃⁻, respectively. The anion clusters are found to each possess a bridging η²-BO group, as well as two terminal BO groups and are analogs of B₂H₃⁻ and B₃H₃⁻. This finding advances the boronyl chemistry and helps establish the isolobal analogy between boron-rich oxide clusters and boranes.