Magnitude and physical origin of intermolecular interactions of aromatic molecules: Recent progress of computational studies

Intermolecular interactions of aromatic molecules (pi/ pi, OH/pi, NH/pi and cation/pi interactions) are important in many fields of chemistry and biology. These interactions are important for crystal structures, stability of biological systems and their molecular recognition processes. Detailed information on the interactions of aromatic molecules is essential for improved material and drug design. However it is not an easy task to study the magnitude and physical origin of these interactions by experimental measurements only. Recent developments of computational methodologies and increasing computer performance enable us to study these interactions qualitatively by high-level ab initio molecular orbital calculations. High-level ab initio calculations are rapidly increasing our knowledge on the intermolecular interactions of aromatic molecules. This review attempts to introduce methodologies for studying weak intermolecular interactions by ab initio calculations and to summarize recent progress in quantitative analysis of intermolecular interactions of aromatic molecules.