Molecular Structure and Charge-Shift Bonding in AlBe7Cl3: A DFT and QTAIM Analysis

The molecular structure and bonding characteristics of the three-winged rotor type molecule AlBe7Cl3, featuring a Be-Al pole, were investigated using density functional theory (DFT). The molecular geometry was optimized at various computational levels, including B3LYP/SBKJC, TPSS/Def2-TZVP, M06/Def2-TZVP, TPSSh/Def2-TZVP, and B3LYP/Lanl2dz, with vibrational frequency calculations confirming structural stability. The molecule exhibits C3v symmetry, and its electronic properties were analyzed using Quantum Theory of Atoms in Molecules (QTAIM) and electron localization functions (ELF). The Be-Cl bonds were found to be highly polar covalent, with electron contributions from Cl ranging from 1.92299 to 1.93557 and from Be between 0.08355 and 0.08495. Electron density maps revealed significant electron localization between planar Be and axial Be atoms, indicating stronger covalent character in Be-Be and Be-Al bonds. The axial Be-Al interaction exhibited weaker bonding due to non-participating Al lone pairs, while steric effects and van der Waals interactions influenced the axial Be-Al interface. These findings provide insights into the electronic structure and bonding interactions within AlBe7Cl3, offering implications for its chemical behavior and potential applications in materials science and catalysis.