Controlling catenations, properties and relative ring-component movements in catenanes with aromatic fluorine substituents

Abstract

Four new fluorine-containing macrocyclic polyethers based on bis-p- phenylene-34-crown-10 have been synthesized and subsequently catenated, separately, with cyclobis(paraquat-p-phenylene). The efficiencies of the catenations are strongly influenced by the aromatic ring templates in the macrocyclic polyethers. Incorporation of fluorine atom substituents into one of the hydroquinone rings in bis-p-phenylene-34-crown-10 had only a small effect on the percentage yields, whereas employing bis-p-phenylene-34-crown- 10 derivatives, in which both hydroquinone rings have been at least partially fluorinated, resulted in a dramatic decrease in catenation yields. In [2]catenanes incorporating macrocyclic polyethers containing one hydroquinone and one fluorinated hydroquinone ring, in both the solution (1H and 19F NMR, and UV-vis spectroscopies, electrochemical studies and molecular modeling) and solid (X-ray crystallography and molecular modeling) states, by far the major translational isomers observed were the ones with the hydroquinone ring located 'inside' the cavity of the tetracationic cyclophane. The diminished strength of the noncovalent interactions arising as a result of aromatic fluorine substituents is also reflected in the rates of the movements of the two ring components (dynamic NMR spectroscopy). As well as their electron-withdrawing effect, the fluorine substituents have a pronounced effect (UV-vis spectroscopy, electrochemical studies and molecular modeling) on the geometry of the ArO-CH2 bonds within the (fluorinated) hydroquinone rings.