Sea-shell-like B31 + and B32: two new axially chiral members of the borospherene family.

Ling Pei,Yue-Wen Mu,Yan-Bo Wu,Si-Dian Li,Miao Yan,Hai-Gang Lu,Xiao-Yun Zhao

doi:10.1039/d0ra01087a

Abstract

Since the discovery of the cage-like borospherenes D2d B40−/0 and the first axially chiral borospherenes C3/C2 B39−, a series of fullerene-like boron clusters in different charge states have been reported in theory. Based on extensive global minimum searches and first-principles theory calculations, we present herein two new axially chiral members C2 B31+ (I) and C2 B32 (VI) to the borospherene family. B31+ (I) features two equivalent heptagons on the top and one octagon at the bottom on the cage surface, while B32 (VI) possesses two equivalent heptagons on top and two equivalent heptagons at the bottom. Detailed bonding analyses show that both sea-shell-like B31+ (I) and B32 (VI) follow the universal σ + π double delocalization bonding pattern of the borospherene family, with ten delocalized π bonds over a σ skeleton, rendering spherical aromaticity to the systems. Extensive molecular dynamics simulations show that these novel borospherenes are kinetically stable below 1000 K. The IR, Raman, and UV-vis spectra of B31+ (I) and B32 (VI) are computationally simulated to facilitate their future experimental characterizations.

Highlights

Based on extensive global minimum searches and first-principles theory calculations, we present two new axially chiral members C2 B31+ (I) and C2 B32 (VI) to the borospherene family
To obtain more accurate relative energies, the top ve lowest-lying isomers of B31+ and B32 were further re ned at the single-point CCSD(T)/6311G(d) level[27,28] at their PBE0/6-311+G(d) geometries with the zero-point energy (ZPE) corrections included at PBE0
Extensive Born–Oppenheimer molecular dynamics (BOMD) simulations were performed for B31+ (I) and B32 (VI) at 500 K, 700 K, and 1000 K for 30 ps (Fig. S2, Electronic supplementary information (ESI)†) using the CP2K so ware,[35] with the GTH-PBE pseudopotential and the DZVP-MOLOPT-SR-GTH basis set adopted

Summary

Introduction

As the lighter neighbour of carbon in the periodic table, boron is a typical electron-de cient element which shares with carbon the rare ability to form stable covalently bonded molecular frameworks with multicentre–two-electron bonds (mc–2e bonds) in both polyhedral molecules and bulk allotropes.[1,2] Persistent joint photoelectron spectroscopy (PES) experimental and rst-principles theory investigations by Lai-Sheng Wang and co-workers in the past two decades on size-selected negatively-charged boron clusters BnÀ (n 1⁄4 3–42) have revealed a rich landscape for boron nanoclusters from planar or quasi-planar (2D) structures (n 1⁄4 3–38, 41, and 42) to cage-like borospherenes (n 1⁄4 39, 40).[3,4,5,6,7,8] The rst all-boron fullerenes D2d B40À/0, dubbed borospherenes, were discovered in 2014, marking the onset of borospherene chemistry.[5]. As the lighter neighbour of carbon, boron is a typical electron-de cient element which shares with carbon the rare ability to form stable covalently bonded molecular frameworks with multicentre–two-electron bonds (mc–2e bonds) in both polyhedral molecules and bulk allotropes.[1,2] Persistent joint photoelectron spectroscopy (PES) experimental and rst-principles theory investigations by Lai-Sheng Wang and co-workers in the past two decades on size-selected negatively-charged boron clusters BnÀ (n 1⁄4 3–42) have revealed a rich landscape for boron nanoclusters from planar or quasi-planar (2D) structures (n 1⁄4 3–38, 41, and 42) to cage-like borospherenes (n 1⁄4 39, 40).[3,4,5,6,7,8] The rst all-boron fullerenes D2d B40À/0, dubbed borospherenes, were discovered in 2014, marking the onset of borospherene chemistry.[5] The spherically aromatic borospherene D2d B40 is found to be composed of twelve interwoven boron double chains with two hexagons at the top and bottom and four heptagons on the waist. The geometrical and electronic structures of Bn+ monocations in the size range between n 1⁄4 30–38 has remained unknown to date, except the sea-shell-like B35+ previously predicted by our group.[17]

Methods

Results

Conclusion