3,6,13,16-Tetrapropylporphycene: Rational Synthesis, Complexation, and Halogenation

We have designed and synthesized 3,6,13,16-tetrapropylporphycene for the first time as its alkyl analogue from ethyl 4-propyl-1H-pyrrole-2-carboxylate. The substituent effect was found to be more intense than reported positional isomeric tetrapropylporphycenes. The freebase porphycene exhibited moderate fluorescence and complexation ability with divalent metal ions, including Zn­(II), which displayed an enhanced emission quantum yield (∼30%). The Pd­(II) complex and freebase β-tetrabromoporphycene generated singlet oxygen efficiently (75 and 51%, respectively) and, hence, may find application as potential photosensitizers in photodynamic therapy.