Octulene: A Hyperbolic Molecular Belt that Binds Chloride Anions

Abstract Octulene, the higher homologue of kekulene and septulene, was synthesized using the fold‐in method. This new hydrocarbon macrocycle contains a large 24‐membered inner circuit, which is peripherally fused to 24 benzene rings. Such an arrangement produces considerable hyperbolic distortion of the π‐conjugated surface. The consequences of distortion in octulene were explored using photophysical methods, which revealed a reduced electronic band gap and greater flexibility of the π system. Octulene contains a functional cavity with a diameter larger than 5.5 Å that is capable of efficiently binding the chloride anion in a nonpolar solvent ( K a = 2.2(4)×10 4 m −1 , 1 % dichloromethane (DCM) in benzene). The octulene–chloride interaction is stabilized by eight weak C(sp 2 )H⋅⋅⋅Cl bonds, providing the first example of a hydrocarbon‐based anion receptor.