Structural and Electronic Properties of LaSi_<i>n</i>^–/0 (<i>n</i> = 2–6) Clusters: Anion Photoelectron Spectroscopy and Density Functional Calculations

Abstract

The structures and electronic properties of LaSi_<i>n</i>^- (<i>n</i> = 2-6) anions and their neutral counterparts were investigated by anion photoelectron spectroscopy and theoretical calculations. The vertical detachment energies of the most stable structures of LaSi_<i>n</i>^- (<i>n</i> = 2-6) were measured to be 1.28, 1.58, 2.30, 2.05, and 2.91 eV, respectively. The lowest-energy isomer of LaSi₂^- is an isosceles triangle with a <i>C</i>_2<i>v</i> symmetry. For LaSi_3-6^- clusters, the most stable isomers are polyhedrons with La atom face-capping the Si_<i>n</i> frameworks. The lowest-energy structures of neutral LaSi_2,4,5 clusters are similar to their anionic counterparts. The most stable isomer of neutral LaSi₃ is a planar structure with <i>C</i>_2<i>v</i> symmetry, which is different from the triangular pyramid structure of LaSi₃^- anion. The lowest-energy isomer of LaSi₆^- is a <i>C</i>_5<i>v</i> symmetric pentagonal bipyramid structure, while for neutral LaSi₆ cluster, the <i>C</i>_5<i>v</i> structure is not the most stable one. The natural population analysis showed that there is electron transfer from La atoms to Si atoms in LaSi_<i>n</i>^-/0 (<i>n</i> = 2-6). The ZZ tensor component in isochemical shielding surfaces and the anisotropy of the induced current density analyses indicate that the most stable isomer of LaSi₆^- has aromaticity.