Synthesis, conformational control, and photothermal application of helically twisted 3,6-carbazole-based porphyrinoids and mono-palladium complex.

Li, Chengming; Zhuang, Weihua; Zhou, Yongjie; He, Linfeng; Yang, Jiayin; Xu, Gang; Su, Rongchuan; Chen, Mao et al. · Nat Commun · 2025

basic_science · Level V

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Abstract

Synthetic control over multiple conformations of expanded porphyrinoids, which are intrinsically linked to their properties and functions, has long been a key objective in chemical research. Here, we present an N-substituent-controlled synthesis of 3,6-carbazole-based octaphyrins and dodecaphyrins via modified Rothemund-type condensation. The choice of pre-modified N-substituents (hydrogen, methyl, tert-butoxycarbonyl) on the 3,6-carbazolylene precursors critically dictates the assembly pathway, enabling access to porphyrinoids with distinct conformations. The octaphyrin scaffold comprises two figure-eight geometries and a half-twisted Möbius form, shaped by solvent-drived kinetic and thermodynamic control. The dodecaphyrins display two helically twisted topologies governed by thermodynamical control. Metalation with Pd(OAc)₂ stabilizes the dynamic twist of octaphyrin into a specific figure-eight geometry, yielding a mono-Pd<sup>II</sup> complex featuring an unconventional NNCC-Pd coordination mode. All these systems exhibit pronounced optical responses to near-infrared light and the mono-Pd<sup>II</sup> complex demonstrates efficient photothermal conversion after encapsulation within nanoparticles, allowing for tumor phototheranostics in the near-infrared bio-window.