In contrast to [24]annulene tetroxide, 5,6,17,18-bisdehydrotetrathia [24]annulene (Figure ), another macrocycle that follows the proposed molecular design, was reported to crystallize in dimers with face-to-face interactions (Figure ), resembling the Ni(II) norcorrole dimers. The dark red needles of the compound showed a melting point of 242 °C. To the surprise of the authors reporting the structure, the macrocycle "has a planar X-ray structure with bent triple bonds and short S-S contacts" but "does not show antiaromatic (paratropic) properties" in solution, confirming that the antiaromaticity is effectively concealed in solution. Interestingly, the crystal structure of the corresponding macrocycle with eight sterically demanding n-butyl chains attached to the thienylene subunits has also been reported (Figure ). Here, the n-butyl chains are considered to hinder close interactions of the 4n π-electron systems in the solid state, resulting in a non-planar, twisted conformation and in yellow crystals with a significantly lower melting point of 116 °C. This shows that macrocycles with concealed antiaromaticity that cannot interact closely with their neighbour(s) in the planar state or prefer other interactions will retain a non-planar conformation in the solid state and, hence, do not feature Type III-CA. However, oxidation of the macrocycle indicated that the compound does feature Type I-CA. An expanded analogue of 5,6,17,18-bisdehydrotetrathia [24]annulene was also shown to crystallize in dimers, whereas a contracted analogue of [24]annulene tetroxide exhibited chain-like packing and Type I-CA. Recently, dimer interactions were also shown for a conformationally restricted phenylene-bridged hexaphyrin with concealed antiaromaticity, despite the presence of sterically demanding substituents. 86