Cyclobis(paraquat‐<i>p</i>‐phenylene). A Tetracationic Multipurpose Receptor

Abstract

The salt 1ṁ4PF6·3CH3CN is a new type of host molecule, which shows similarities to zeolites but is constructed from organic and inorganic ions. The macrocyclic tetracation 1 can be prepared in two steps from bipyridine and 1,4-bis(bromomethyl)benzene. Calculations and X-ray crystallography showed the tetracation to have a box-like structure in which the p-phenylene and paraquat units are slightly bent. The PF-salt of 1 is soluble in organic solvents, the Cl⊖ salt in water. 1·4PF6 in acetonitrile forms weak inclusion complexes with dimethoxybenzenes, which are stabilized by charge-transfer interactions. Structural studies of the inclusion complexes show that the electron-rich guest molecules are located in the cavities (2); because of the stapling of the alternating tetraction and anion/neutral molecule layers these cavities take the form of channels.