Global minimum and a heap of low-lying isomers with planar tetracoordinate carbon in the CAl₃MgH₂^- system

A global minimum and a heap of low-lying isomers with planar tetracoordinate carbon (ptC) are identified in the CAl₃MgH₂^- system by computational quantum chemical investigations. The nature of the chemical bonding in the global minimum ptC isomer is examined using the conceptual quantum chemical tools. The atoms in molecule (AIM) analysis reveals that the global minimum isomer possesses a ptC geometry. Additionally, the adaptive natural density partitioning (AdNDP), electron localization function (ELF), and nucleus-independent chemical shifts (NICS) analysis corroborate the presence of delocalization in the ptC isomer. The delocalization of electron density in the global minimum ptC isomer contributes to attaining structural stability. The results also suggest that the bridging hydrogen plays a crucial role in stabilizing the ptC system. Furthermore, the ab initio molecular dynamics study supports the structural stability of the ptC isomer.