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The Viologen Cation Radical Pimer: A Case of Dispersion‐Driven Bonding
Author(s) -
Geraskina Margarita R.,
Dutton Andrew S.,
Juetten Mark J.,
Wood Samuel A.,
Winter Arthur H.
Publication year - 2017
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201704959
Subject(s) - radical , chemistry , viologen , stacking , dispersion (optics) , london dispersion force , steric effects , molecule , cationic polymerization , photochemistry , polarizability , crystallography , chemical physics , computational chemistry , van der waals force , stereochemistry , organic chemistry , physics , optics
The π bonds between organic radicals have generated excitement as an orthogonal interaction for designing self‐assembling architectures in water. A systematic investigation of the effect of the viologen cation radical structure on the strength and nature of the pimer bond is provided. A striking and unexpected feature of this π bond is that the bond strength is unchanged by substitution with electron‐donating groups or withdrawing groups or with increased conjugation. Furthermore, the interaction is undiminished by sterically bulky N ‐alkyl groups. Theoretical modeling indicates that strong dispersion forces dominate the interaction between the radicals, rationalizing the insensitivity of the bonding interaction to substituents: The stacking of polarizable π radicals leads to attractive dispersion forces in excess of typical dispersion interactions of small molecules and helps overcome the Coulombic repulsion of bringing two cationic species into contact.