Dynamical fluxionality, multiplicity of geometrical forms, and electronic properties of anionic, neutral, and cationic Ta_nSi₁₂ (n = 1–3) clusters: quantum chemical calculations

The dynamical fluxionality, multiplicity of geometrical forms, and electronic properties of anionic, neutral, and cationic Ta_nSi₁₂ (n = 1–3) clusters are studied by quantum chemical calculations. The results show that $T{a}_n{Si}_{12}^{-/0/+}$ (n = 1–3) clusters are dominated by prism-based geometries. Impressively, neutral and cationic Ta_nSi₁₂ (n = 1–3) clusters have multiple geometrical forms and their low-lying isomers exhibit dynamical fluxionality. $T{a}_1{Si}_{12}^{-}$ is a D_6h symmetric Ta-endohedral Si₁₂ hexagonal prism with highly electronically stability because of satisfying the 18-electrons rule, and having a closing-shell electronic configuration with a large HOMO–LUMO gap of 2.81 eV and delocalised Ta-Si₁₂ ligand interactions. $T{a}_1{Si}_{12}^{0/+}$ clusters have a C_2v symmetric Ta-endohedral bicapped pentagonal prism. In $T{a}_2{Si}_{12}^{-/0/+}$, a Si₅ pentagonal ring and a Si₇ heptagonal ring are bridged by the Ta−Ta bonding axis, which is perpendicular to the Si₅ and Si₇ frameworks. $T{a}_3{Si}_{12}^{-}$ adopts a bicapped hexagonal antiprism with one Ta atom encapsulated into the TaSi₁₁ hexagonal antiprism, whereas neutral and cationic Ta₃Si₁₂ hold a TaSi₅ hexagon and a Si₇ heptagon penetrated by the vertical Ta−Ta bond. The Ta atoms in $T{a}_n{Si}_{12}^{-/0/+}$ (n = 2–3) clusters have strong bonding interactions and the charges are transferred from the Si₁₂ frameworks to the Ta atoms.