Arene-perfluoroarene interaction

Similar structures have been observed for a variety of other arene-perfluoroarene complexes [15], indicating that this kind of interaction is a generally occurring phenomenon for this type of structure [18], Evidence based on structural [17] and spectroscopic data [19[, and on quantum chemical calculations [20] (Figure 1.8) indicates, that the observed arene-perfluoroarene interactions are mainly the consequence of strong quadrupolar electrostatic attraction [21]. 

Coliings, J.C. Roscoe. K.P. Robins. E.G. Batsanov, A.S. Stimson. L.M. Howard, J.A.K. Clark, S.J. Marder. T.B. Arene-perfluoroarene interactions in crystal engineering 8 Structures of 1 1 complexes of hexafluorobenzene with fused-ring polyaromatic hydrocarbons. New J. Chem. 2002. 26. 1740-1746. 

Figure 10 Arene-perfluoroarene interactions in rigid-rod mesogens.

One novel interaction that has been established as a way to design solids is the arene-perfluoroarene interaction. 

The remarkably low reactivity of tetrafluoroparacyclophane (29) to Friedel-Crafts acylation in comparison with para-xylene indicates the deactivation of the nonfluorinated aromatic ring of 29 because of electron-deficiency due to a through-space polarization (Scheme 1.33) [26]. The tt-tt stacking interaction between arenes and perfluoroarenes has been employed for modification of the liquid crystals [27]. 

Week, M. et al.. Influence of perfluoroarene-arene interactions on the phase behavior of... 

A few solvents exhibit intermediate properties. For example, both BTF (Ref. 22) and F-626 (Ref. 23 see Section 3.1) are able to dissolve appreciable quantities of both fluorous and non-fluorous solutes. Other solvents are often mistakenly assumed to be fluorous. Of these, the most important are perfluoroarenes such as hexafluo-robenzene. The arene tt clouds and sp carbon-fluorine bonds lead to significant intermolecular bond dipoles, induced dipoles and quadrupolar interactions with non-fluorous molecules. ... 

The perfluoroarene effect has also been probed using cyclophane systems. In particular the interaction of a cation with an arene and a fluorinated arene has been probed in several systems. An interesting comparison between the it effects found for standard arenes and perfluoroarenes can be made simply by examining the electrostatic surface maps shown in Appendix 2 for benzene and hexafluorobenzene. The charges derived from the quadrupole moments for benzene and hexafluorobenzene are opposite on the faces of the arenes, negative for benzene (red in Appendix 2) and positive for hexafluorobenzene (blue in Appendix 2). As expected, fluorination turns an attractive cation-ir interaction into a repulsive cation-fluoroarene interaction, and the difference can be on the order of several kcal / mol. 

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