Chemical Bonding and Dynamic Structural Fluxionality of a Boron-Based B₈Al₃⁺ Cluster

Area of Science:

• Computational Chemistry
• Materials Science
• Quantum Chemistry

Background:

• Boron clusters are known for their unique structural and electronic properties.
• Aluminum doping can significantly alter the stability and characteristics of boron clusters.

Purpose of the Study:

• To investigate the global minimum structure and electronic properties of the B8Al3+ cluster.
• To explore the dynamic behavior and aromaticity of this novel boron-aluminum composite cluster.

Main Methods:

• Density Functional Theory (DFT) calculations for structural optimization.
• Born-Oppenheimer Molecular Dynamics (BOMD) simulations for dynamic analysis.
• Coupled Cluster Singles, Doubles, and Triples (CCSD(T)) calculations for energy barrier determination.

Main Results:

• The global minimum structure of B8Al3+ features a three-layer arrangement: an Al2 unit, a B8 ring, and an isolated Al atom.
• Charge analysis reveals a [Al]+[B8]2-[Al2]2+ configuration with 6π/6σ double aromaticity, adhering to the (4n+2) Hückel rule.
• BOMD simulations and low energy barriers (0.19 kcal mol-1) indicate significant dynamic fluxionality.

Conclusions:

• The B8Al3+ cluster demonstrates remarkable dynamic structural fluxionality, driven by the double aromaticity of the [B8]2- molecular wheel.
• This study presents a new example of dynamic fluxionality in complex molecular systems, expanding our understanding of boron-based clusters.