Understanding the Fundamental Role of π/π, σ/σ, and σ/π Dispersion Interactions in Shaping Carbon‐Based Materials

Abstract

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.

Compressed representation of dispersion interactions and long-range electronic correlations

“…This is in agreement with other literature findings. [60][61][62] We also verified that the relative contribution of σ and π electrons was well-represented by our approximate T disp 2 (see Supporting Information for a more detailed discussion).…”

The influence of asphaltene-resin molecular interactions on the colloidal stability of crude oil

“…A tilted Tshape with the minimum electron repulsion between two fragments is the most favorable conformer for simple p-stacking structures like a benzene dimer [83][84][85]45], whereas theoretical studies on PAHs show that parallel or nearly parallel stacking structures are preferred over T-oriented structures [86,28]. This could be attributed to the steric repulsion between aliphatic side chains of two molecules in T-shape structures [87].…”

“…To accurately describe p-stacking interactions, as well as to emphasize the importance of dispersion energy as a key factor in stabilizing the stacked dimers, dispersion-corrected DFT functional, B97-D [43], associated with basis sets 6-31G ⁄ and 6-311+G ⁄⁄ , was selected as the level of DF calculations to optimize the structures. Recently, B97-D has been widely used to describe macro structures like asphaltene sheets and DNA-base pairs [44][45][46][47][48] Counterpoise (CP) correction [49,50] was performed to limit basis set superposition error (BSSE) while studying intermolecular interactions.…”

London’sche Dispersionswechselwirkungen in der Molekülchemie – eine Neubetrachtung sterischer Effekte

“…[96] Schließlich kçnnen auch Methoden der Va lenzbindungstheorie zur Analyse der Wellenfunktion zur Gewichtung der LD genutzt werden;d iese unterstreicht unter anderem die Bedeutung alternierender Dipolstrukturen im Sinne von Londons ursprünglicher Formulierung der Dispersion. [97] Während dieser Ansatz bei kleinen Molekülen gut funktioniert, müssen für beispielsweise grçßere Alkane die Elektronen der primär wechselwirkenden C-H···H-C-Bindungen neu gekoppelt werden, um den Hauptanteil der Wechselwirkungsenergie zu erfassen.…”

“…[82,107] Diese Schlussfolgerung wurde unabhängig bestätigt [107] und insofern weiterentwickelt, als dass s-s-und s-p-Wechselwirkungen als lokal betrachtet werden kçnnen, während die p-p-Stapelung inhärent nichtlokal ist und nichtadditive Effekte ermçg-licht. [96] Weiterhin werden diese Wechselwirkungen von…”