Stacking of fluoroaromatics

The stereospecific solid-state [2 + 2] photocyclization of cocrystals 14 proceeded in a stereospecific manner to form 15 [19]. The pentafluorophenyl-phenyl tt-tt interaction in the solution state has been demonstrated in the Pd-catalyzed synthesis of acetylenic cyclo-phanes (17) via inter- and then intramolecular self-assembly as shown in the transformation 

The photochromic behavior of the diarylethene crystals can be controlled by crystal engineering, namely the use of the it-it stacking phenomenon. Pentafluorophenyl substituted 

6 Increasedp-character (Bent s rule) and low-lying LUMO in carbon-fluorine bonding orbitals 

Bent s rule describes that atomic p-character concentrates in the orbitals directed toward electronegative substituents [ 1 ]. Therefore, a carbon-fluorine bond bears a more p-character in the bonding orbital because of the strongly electronegative fluorine atom. On the other 

The highly exothermic cesium fluoride catalyzed isomerization of hexafluorobutadiene (9) via 10 to hexafluoro-2-butyne (11) is another example [5] that shows that the fluorine atom is preferably bonded to the carbon atom through the sp3-hybridized orbital rather than through the sp2 orbital [6]. And here again, Bent s rule plays an important role in the isomerization [7]. The thermal reaction of hexafluoro-1,3-butadiene provides perfluorotricyclo[3.2.0.02,6]octane (15) as a stable final product via sequential intra-and/or intermolecular cycloaddition at 200°C [8]. In contrast, the parent hydrocarbon (16) 

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