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-pi 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-7r 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.