Is the T-Shaped Toluene Dimer a Stable Intermolecular Complex?

By means of molecular mechanics and ab initio calculations, we show that toluene dimer can assume two different minimum energy structures. Both these arrangements are stacked with the methyl groups being parallel and anti-parallel to each other. Although our findings do not agree with the current opinion that one minimum energy structure is T-shaped, they appear to be consistent with available experiments on jet-cooled toluene.