Exploring novel aluminum chemistry using quantum mechanical computations

Quantum mechanical computational methods are applied to a variety of aluminum-containing molecules. A novel recently-synthesized organoaluminum compound, bis-pentamethylcyclopentadienyl diiododialane (Cp*2Al2I2), was investigated using density functional and ab initio methods. A family of twenty related compounds was constructed to systematically investigate halogen and ligand effects. Electronic effects are most important in species with small alkyl ligands (H or methyl), while steric repulsions dominate in species with bulky ligands (cyclopentadienyl or pentamethylcyclopentadienyl). These effects were discussed in detail using natural bond orbital analysis. Next, the small molecules AlCH2 and AlCH2+ were investigated using highly accurate ab initio methods. There is an Al-C single bond in the neutral, but the Al-C interaction in the cation is a half-bond. Both are thermodynamically stable with respect to dissociation, and may be observable in the interstellar medium. Highly accurate spectroscopic constants were computed to aid astrochemists in identifying these species.