Understanding the fundamental role of π/π, σ/σ, and σ/π dispersion interactions in shaping carbon-based materials.
Noncovalent interactions involving aromatic rings, such as π-stacking and CH/π interactions, are central to many areas of modern chemistry. However, recent studies proved that aromaticity is not required for stacking interactions, since similar interaction energies were computed for several aromatic and aliphatic dimers. Herein, the nature and origin of π/π, σ/σ, and σ/π dispersion interactions has been investigated by using dispersion-corrected density functional theory, energy decomposition analysis, and the recently developed noncovalent interaction (NCI) method. Our analysis shows that π/π and σ/σ stacking interactions are equally important for the benzene and cyclohexane dimers, explaining why both compounds have similar boiling points. Also, similar dispersion forces are found in the benzene⋅⋅⋅methane and cyclohexane⋅⋅⋅methane complexes. However, for systems larger than naphthalene, there are enhanced stacking interactions in the aromatic dimers adopting a parallel-displaced configuration compared to the analogous saturated systems. Although dispersion plays a decisive role in stabilizing all the complexes, the origin of the π/π, σ/σ, and σ/π interactions is different. The NCI method reveals that the dispersion interactions between the hydrogen atoms are responsible for the surprisingly strong aliphatic interactions. Moreover, whereas σ/σ and σ/π interactions are local, the π/π stacking are inherently delocalized, which give rise to a non-additive effect. These new types of dispersion interactions between saturated groups can be exploited in the rational design of novel carbon materials.
['Alonso|Mercedes|M|', 'Woller|Tatiana|T|', 'Martín-Martínez|Francisco J|FJ|', 'Contreras-García|Julia|J|', 'Geerlings|Paul|P|', 'De Proft|Frank|F|']
D001554:Benzene D002244:Carbon D003510:Cyclohexanes D019281:Dimerization D008958:Models, Molecular D009281:Naphthalenes D011789:Quantum Theory D012965:Sodium Chloride D013816:Thermodynamics
dispersion noncovalent interactions aromaticity density functional calculations