Standard Classification of Intermolecular Interactions

Over recent decades, a couple of intermolecular interaction patterns have been identified and refined in order to facilitate understanding of supramolecular processes. The decomposition of a whole interaction pattern into individual contributions is somewhat artificial - only the total interaction energy is well defined - but it is required for our classical, macroscopic view and understanding of these processes. The following list of interaction types contains a few important ones but cannot be considered complete (for instance, magnetic fields or reversibly built and broken covalent bonds are completely neglected)  

Dipole interactions are usually weaker than electrostatic monopole interactions but can dominate the intermolecular interactions within a supramolecular assembly. Diederich and coworkers have recently drawn attention onto dipole interactions, and multipolar interactions in general, in such systems based on a statistical analysis of structures [180]. 

Higher and mixed multipole interactions are also always present and may play a dominant role in the absence of lower multipole moments, especially in the absence of mono- and dipoles. Note also that these electrostatic multipole interactions are purely classic and typical quantum mechanical effects (like Pauli repulsion etc.) are not captured. 

It is important to note that weak hydrogen bonds must not be neglected in multi-valent host-guest interactions as their contribution to the interaction energy can be decisive and can thus determine the structure of a supramolecular assembly (see Refs. [184, 188, 189] for general accounts on weak hydrogen bonds, Ref. [190] for weak C-H F-C interactions, and Refs. [59, 175] for weak C-H O= contacts). 

For a stationary, time-independent equilibrium structure (in the quantum chemical sense) all these effects can in principle be captured at once by the electronic wave function 

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