“…The breakdown of such species via the opening of the macrocycle is crucial for various biological processes, such as heme degradation, leaf senescence, and fruit ripening. − A key step is the attack of the macrocycle by oxygenase, inducing the ring-opening and constituting distinct tetrapyrrole catabolites. − Together with the intricate macrocycle-opening reactions that might proceed with or without loss of carbon atoms, , the products are of pivotal relevance. For example, bilirubin, a heme catabolite, can further oxidatively react to form tripyrrins. , Such oligopyrroles likewise attracted attention from a material science perspective, for example, di- and tripyrrins can be employed as metal–complexing agents in functional organometallic compounds , and as fluorescent sensors. , Furthermore, the synthesis of artificial porphyrinoids, with expanded, contracted, or otherwise modified macrocycles, frequently relies on precursors combining one, two, or three pyrrolic units . Interfacial nanoscience has provided manifold insights into surface-supported tetrapyrrole systems and their rich chemistry, , frequently exceeding the scope of typically stability-limited characterization in solution.…”