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Pi interaction

About: Pi interaction is a research topic. Over the lifetime, 593 publications have been published within this topic receiving 25804 citations.


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TL;DR: The CH/π interaction is a kind of hydrogen bond operating between a soft acid CH and a soft base π-system (double and triple bonds, C6 and C5 aromatic rings, heteroaromatics, convex surfaces of fullerenes and nanotubes) as discussed by the authors.
Abstract: The nature and characteristics of the CH/π interaction are discussed by comparison with other weak molecular forces such as the CH/O and OH/π interaction. The CH/π interaction is a kind of hydrogen bond operating between a soft acid CH and a soft base π-system (double and triple bonds, C6 and C5 aromatic rings, heteroaromatics, convex surfaces of fullerenes and nanotubes). The consequences of CH/π hydrogen bonds in supramolecular chemistry are reviewed on grounds of recent crystallographic findings and database analyses. The topics include intramolecular interactions, crystal packing (organic and organometallic compounds), host/guest complexes (cavity-type inclusion compounds of cyclodextrins and synthetic macrocyclic hosts such as calixarenes, catenanes, rotaxanes and pseudorotaxanes), lattice-inclusion type clathrates (including liquid crystals, porphyrin derivatives, cyclopentadienyl compounds and C60 fullerenes), enantioselective clathrate formation, catalytic enantioface discriminating reactions and solid-state photoreaction. The implications of the CH/π concept for crystal engineering and drug design are evident.

1,262 citations

Journal ArticleDOI
TL;DR: The dual characteristic of the CH/π hydrogen bond is the basis for ubiquitous existence of this force in various fields of chemistry and extends to the specificity of molecular recognition or selectivity in organic reactions, polymer science, surface phenomena and interactions involving proteins.
Abstract: The CH/π hydrogen bond is an attractive molecular force occurring between a soft acid and a soft base. Contribution from the dispersion energy is important in typical cases where aliphatic or aromatic CH groups are involved. Coulombic energy is of minor importance as compared to the other weak hydrogen bonds. The hydrogen bond nature of this force, however, has been confirmed by AIM analyses. The dual characteristic of the CH/π hydrogen bond is the basis for ubiquitous existence of this force in various fields of chemistry. A salient feature is that the CH/π hydrogen bond works cooperatively. Another significant point is that it works in nonpolar as well as polar, protic solvents such as water. The interaction energy depends on the nature of the molecular fragments, CH as well as π-groups: the stronger the proton donating ability of the CH group, the larger the stabilizing effect. This Perspective focuses on the consequence of this molecular force in the conformation of organic compounds and supramolecular chemistry. Implication of the CH/π hydrogen bond extends to the specificity of molecular recognition or selectivity in organic reactions, polymer science, surface phenomena and interactions involving proteins. Many problems, unsettled to date, will become clearer in the light of the CH/π paradigm.

701 citations

Journal ArticleDOI
TL;DR: The CH/π interaction is a weak molecular force occurring between CH groups and π-groups as mentioned in this paper, and it has been found that the CH hydrogen atoms tend to point toward the center of the aromatic ring.
Abstract: The CH/π interaction is a weak molecular force occurring between CH groups and π-groups. A study was carried out by use of the Cambridge Structural Database in order to obtain insights into the nature of the CH/π interaction and to examine its role in the crystal packing. The proportion of organic molecules bearing at least one CH/π interaction in their crystal structures has been found considerable. The CH hydrogen atoms tend to point toward the center of the aromatic ring. A number of short CH/π distances have been shown in the crystal structures of organic compounds. Moreover, the mean CH/π distance decreases as the acidity of the CH group increases. These results suggest that the CH/π interaction is not simply due to the dispersion force but involves other types of interactions, which are orientation-dependent and effective at wider ranges. It was suggested that the CH/π interaction constitutes one of the important factors in controlling the crystal packing of molecules.

368 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20221
20212
20203
20193
20186
201713