N-Aryl Substituted Carbazoliporphyrins

A new class of carbazole-containing carbaporphyrinoids, which are challenging to access by conventional condensation methods, was successfully synthesized through a postsynthetic Pd-catalyzed amination strategy using a dibrominated carbaporphyrin precursor and various aryl amines. The formed carbaporphyrins can be termed as carbazoliporphyrins, which feature a compact adj-CCNN tetradentate cavity. Spectroscopic characterization and density functional theory (DFT) calculations reveal that the freebase carbazoliporphyrins exhibit weak antiaromatic character, which can be tuned through electronic variation of the nitrogen substituent. Metalation with copper further alters their electronic structures, leading to narrowed HOMO–LUMO gaps and pronounced red-shifted absorptions extending into the near-infrared region. Femtosecond transient absorption reveals that freebase carbazoliporphyrins undergo ultrafast distortion-driven nonradiative decay, whereas Cu-metalated derivatives exhibit markedly prolonged excited-state lifetimes despite negligible fluorescence, consistent with ligand-to-metal charge transfer into metal-dominant excited states. This work represents the first synthesis of carbazoliporphyrin as a distinct fundamental carbaporphyrinoid framework and may provide a new access to more complex carbaporphyrinoid architectures.