The characteristic absorption bands of porphyrinoids are displayed for an example of tetraphenyl PP (see Supporting Information [SI], Figure ). The intense Soret-band, also called B-band, commonly arises in the UV from 350 to 450 nm. In metal free porphyrins, four transitions with much lower intensity are found in the spectral range from 450 to 800 nm, which are called Q-bands. All transitions between the frontier orbitals are allowed based on symmetry rules. However, both highest occupied molecular orbitals (HOMO-1 and HOMO) as well as both lowest unoccupied molecular orbitals (LUMO and LUMO+1) are close in energy and thus, nearly degenerated as in a simplified model of a 18π cyclic polyene, as employed by . In this model, two transitions are allowed between the degenerated frontier orbitals while two are forbidden. Indeed, the frontier molecular orbitals of porphyrin and the model system show strong similarities. Furthermore, a strong mixing of the transitions was observed for Q-and Soret bands by quantum chemical calculations. Opposing transition dipoles reduce the intensity of the Q-bands while a parallel orientation of both transition dipoles contributes to the Soret band and thus, a more intense absorption band is observed for the latter.