La@[La5&B30]0/−/2−: endohedral trihedral metallo-borospherenes with spherical aromaticity

Abstract

It is well-known that transition-metal-doping induces dramatic changes in the structures and bonding of small boron clusters, as demonstrated by the newly observed perfect inverse sandwich D_8h [La(η⁸-B₈)La] and D_9h [La(η⁹-B₉)La]⁻. Based on extensive global minimum searches and first-principles theory calculations, we predict herein the possibility of perfect endohedral trihedral metallo-borospherene D_3h La@[La₅&B₃₀] (1, ³A′₁) and its monoanion C_s La@[La₅&B₃₀]⁻ (2, ²A′) and dianion D_3h La@[La₅&B₃₀]²⁻ (3, ¹A′₁). These La-doped boron clusters are composed of three inverse sandwich La(η⁸-B₈)La on the waist and two inverse sandwich La(η⁹-B₉)La on the top and bottom which share one apex La atom at the center and six periphery B₂ units between neighboring η⁸-B₈ and η⁹-B₉ rings, with three octo-coordinate La atoms and two nona-coordinate La atoms as integrated parts of the cage surface. Detailed adaptive natural density partitioning (AdNDP) and iso-chemical shielding surface (ICSS) analyses indicate that La@[La₅&B₃₀]^0/−/2− (1/2/3) are spherically aromatic in nature. The one-dimensional nanowire La₄B₂₁ (4, P31m) constructed from D_3h La@[La₅&B₃₀] (1) along the C₃ axis of the system appears to be metallic. The IR and Raman spectra of La@[La₅&B₃₀] (1) and photoelectron spectroscopy of the slightly distorted C_s La@[La₅&B₃₀]⁻ (2) are theoretically simulated to facilitate their spectroscopic characterizations.