Stacking interaction between homostacks of simple aromatics and the factors influencing these interactions

The intermolecular pi-pi stacking interactions within the homostacks (X-X type stacking) of simple aromatic molecules in crystal structures extracted from the Cambridge crystallographic database are reported here. It is found that the stacking interactions in crystals of simple aromatic hydrocarbons become important only for molecules with more than three rings. Whereas for crystals of nitrogen substituted heterocyclic aromatic molecule, the stacking interactions become important for doubly substituted single ringed molecules itself. We investigated some of the factors that affect the stacking interactions between these molecules viz the substitution of a hydrogen atom of a simple aromatic hydrocarbons and the formation of a hydrogen bonds were the nitrogen substituted heterocyclic aromatic molecule acts as a hydrogen bond acceptor. Molecular electron density parameters obtained from the theoretical quantum calculations using the package GAMESS UK are used to explain the results obtained from data mining.