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.

尽管氟通常在分子识别（molecular recognition）中发挥重要作用，但目前学界对溶液中脂肪族氟（aliphatic fluorine）对CH−π相互作用的影响仍知之甚少。本研究合成了一系列带有氟化与非氟化烷基的分子天平（molecular balances）。研究结果表明，氟的极化能力确实能够增强CH−π结合作用，且该效应依赖于分子取向。令人意外的是，当烷基末端完全氟化时，分子天平的平衡会转向疏氟性，并呈现出一种罕见的受限构象。