Unraveling the Role of Alkyl F on CH−π Interactions and Uncovering the Tipping Point for Fluorophobicity

Although
fluorine often plays an influential role in molecular
recognition, little is known about the effect of aliphatic fluorine
on the CH−π interaction in solution. A series of molecular
balances were synthesized that contain fluorinated and nonfluorinated
alkyl groups. Our findings indicate that fluorine’s polarizing
ability does enhance CH−π binding and depends on molecular
orientation. Surprisingly, when the terminal end of the alkyl group
is completely fluorinated, the balance tips toward fluorophobicity
and assumes an unusual constrained conformation.