As a potential alternative to the attachment of side chains, there are reports indicating that macrocyclization can increase the solubility of conjugated molecules. For molecules with alternating p-phenylene and vinylene units, as known from the iconic class of conjugated polymers poly(p-phenylene vinylene)s (PPVs), this solubilizing effect appears to be particularly strong: PPVs without side chains cannot be dissolved and processed from solution. Even for oligomers with only four phenylene units (Scheme 1, top left), extremely low solubility has been observed, with the solubility of the reported E-isomer found to be insufficient for 1 H NMR measurements. In contrast, the corresponding macrocycle, paracyclophanetetraene (PCT; Scheme 1, top center), dissolves well in various organic solvents and the compound can be easily processed from solution. Furthermore, conjugated macrocycles can also act as redox-active units, meaning that, unlike the attachment of aliphatic side chains, macrocyclization may even increase the specific capacity for use as a battery electrode material. In the case of PCT and its derivatives, the macrocyclic structure enables switching between a stable, locally aromatic neutral state (with concealed antiaromaticity) and a stable, globally aromatic doubly charged state (Scheme 1, top right), providing these macrocycles with excellent redox properties. The macrocyclic geometry has also been shown to result in a high degree of porosity of the single crystals of these molecules, another valuable feature for battery electrodes and other applications. Scheme 1. Top: Molecular design of paracyclophanetetraene (PCT) by macrocyclization of oligo(p-phenylenevinylene)s. Bottom: Integration of PCT into conjugated polymers by copolymerization with (bi)thiophene derivatives, as reported in this work.