From inverse sandwich Ta(2)B(7)(+)and Ta(2)B(8)to spherical trihedral Ta3B12-: prediction of the smallest metallo-borospherene

Transition-metal-doped boron nanoclusters exhibit interesting structures and bonding. Inspired by the experimentally discovered inverse sandwichD(6h)Ta(2)B(6)and spherical trihedralD(3h)La(3)B(18)(-)and based on extensive first-principles theory calculations, we predict herein the structural transition from perfect di-metal-doped inverse sandwichD(7h)Ta(2)B(7)(+)(1) andD(8h)Ta(2)B(8)(2) to tri-metal-doped spherical trihedralD(3h)Ta(3)B(12)(-)(3). As the smallest metallo-borospherene reported to date, Ta3B12-(3) contains three octa-coordinate Ta atoms as integral parts of the cage surface coordinated in three equivalent eta(8)-B(8)rings which share two eclipsed equilateral B(3)triangles on the top and bottom interconnected by three B(2)units on the waist. Detailed orbital and bonding analyses indicate that both Ta2B7+(1) and Ta2B8(2) possess sigma + pi dual aromaticity, while Ta3B12-(3) is sigma + pi + delta triply aromatic in nature. The IR, Raman, and UV-vis or photoelectron spectra of the concerned species are computationally simulated to facilitate their future spectroscopic characterizations.