Two porphyrin‐cored thiophene dendrimers T(3T)P and T(7T)P have been successfully synthesized and characterized by UV‐vis and fluorescence measurements. The self‐assembly of these two water‐insoluble free base porphyrins to form both intrinsic H‐ and J‐aggregates has been reported for the first time. This intrinsic behavior is in contrast to the use of surfactants, dyes, and metal ions to induce aggregation behavior on most porphyrin systems. This work emphasizes the importance of controlling the size, solvent, and extent of conjugation of polythiophene dendron groups in porphyrin systems. These materials may yet be applied to polythiophene or porphyrin blend system in energy conversion devices with the light‐harvesting properties of the polythiophene dendrons.
