The synthesis of porphyrin–anthraquinone dyad via an azo-rearrangement

One novel porphyrin P-Q2 is planned to be synthesized by condensation between ATPP and Q1. However, after separation by chromatography and characterization with IR, 1H NMR, HR-MS and X-ray, P-Q1 is obtained unexpectedly. Compared the structure of P-Q1 with that of P-Q2, it is realized that an intramolecular cyclization rearrangement takes place when the azo group is situated in the o-position to the amido group. This rearrangement offers a new way to prepare indazole heterocycle. In addition, the spectral properties of P-Q1 have been studied by UV–vis and steady state fluorescence spectroscopy. Strong fluorescence quenching is observed in the preliminary emission spectrum due to the proposed electron transfer from the excited porphyrin to the anthraquinone moieties.