Elucidating the Nature of Carbazole-Porphyrinoids with First-Principle Approaches

Carbazole-porphyrinoids are [20]porphyrins that can be oxidized to the so-called porphyrin state, inducing a huge shift of the main absorption band from the UV-visible to the infrared region. In this study, we focus on the compound synthesized by Arnold and co-workers [ Arnold , L. ; Baumgarten , M. ; Müllen , K. A. Chem. Commun. , 2012 , 48 , 9640 - 9642 ], where the two pyrroline units of a porphyrin are replaced with carbazole moieties. Due to the poor stability of these macrocycles, the nature of the oxidation product could not be definitively ascertained experimentally. In that framework, with the help of ab initio approaches, we investigate the structure, the stability, the aromaticity, and the spectroscopic signatures of both the nonoxidized compound and a series of possible oxidation products. Thanks to vibronic simulations, we obtain insights into the nature of the oxidized macrocycle.