CB₆Al^0/+: Planar hexacoordinate boron (phB) in the global minimum structure.

Area of Science:

• Computational Chemistry
• Inorganic Chemistry
• Materials Science

Background:

• Planar hexacoordinate boron (phB) is a rare and intriguing structural motif.
• Previous studies have not identified phB in neutral cluster systems.
• Understanding the factors enabling phB formation is crucial for designing novel materials.

Purpose of the Study:

• To investigate the possibility of planar hexacoordinate boron in neutral CB6Al systems.
• To explore the role of aluminum in stabilizing such structures.
• To determine the electronic and aromatic properties of the resulting clusters.

Main Methods:

• Density Functional Theory (DFT) for potential energy surface exploration.
• Coupled Cluster with Single, Double, and Triple Excitations (CCSD(T)) for accurate energy calculations.
• Atom-Centered Density Matrix Propagation (ADMP) for dynamical stability simulations.
• Natural charge and Nucleus-Independent Chemical Shift (NICS) for electronic property analysis.

Main Results:

• The global minima of CB6Al and CB6Al+ were found to contain a planar hexacoordinate boron (phB) center.
• CB6Al- global minimum does not exhibit a phB structure, highlighting the role of charge and composition.
• Aluminum incorporation was essential for stabilizing the phB moiety in CB6Al and CB6Al+.
• Dynamical stability simulations confirmed the robustness of CB6Al and CB6Al+ at elevated temperatures.
• The phB atom in CB6Al and CB6Al+ carries near-zero natural charge.
• The CB6Al structure exhibits both sigma and pi dual aromaticity, confirmed by NICS and GIMIC analyses.

Conclusions:

• This study reports the first observation of a planar hexacoordinate boron atom in a neutral cluster system (CB6Al and CB6Al+).
• Aluminum plays a critical role in the formation and stabilization of the phB center.
• The discovered CB6Al structure possesses unique electronic properties, including dual aromaticity, opening avenues for new chemical insights.