Xanthene Separated 24 π‐Electron Antiaromatic Rosarin Dimer

Antiaromatic molecules have recently received attention because of their intrinsic properties, such as high reactivity and their narrow HOMO-LUMO gaps. Stacking of antiaromatic molecules has been predicted to induce three-dimensional aromaticity via frontier orbital interactions. Here, we report a covalently linked π-π stacked rosarin dimer that has been examined experimentally by steady-state absorption and transient absorption measurements and theoretically by quantum chemical calculations, including TD-DFT, ACID, and NICS. Relative to the corresponding monomer, the dimer exhibits diminished antiaromaticity upon lowering the temperature to 77K, a finding ascribed to intramolecular interactions between the macrocyclic rosarin subunits.