A Triply Linked Porphyrin‐Norcorrole Hybrid with Singlet Diradical Character

meso–meso, β–β, β–β Triply-linked porphyrin–norcorrole hybrids and meso–meso singly-linked hybrids were synthesized through intramolecular homocoupling of precursors, respectively. The molecular structures of porphyrin–norcorrole hybrids have been confirmed by X-ray diffraction analysis. The triply-linked hybrid exhibits a warped structure and shows a significantly small electrochemical HOMO–LUMO gap (0.45 eV). Furthermore, the triply-linked hybrid displays singlet diradical characteristics.

Abstract

Norcorrole Ni(II) complexes have recently received considerable attention because they are readily accessible antiaromatic molecules. Their high stability under ambient conditions and ease of synthesis have enabled the exploration of the intrinsic properties of antiaromatic molecules. Here, we report the synthesis and properties of meso–meso singly linked porphyrin-norcorrole hybrids and a triply linked porphyrin-norcorrole hybrid. The singly linked and triply linked porphyrin-norcorrole hybrids were fully characterized, including an X-ray structural analysis. Due to their orthogonal conformation, the singly linked hybrids maintain the individual electronic properties of their porphyrin and norcorrole subunits, while the triply linked hybrid shows a significantly smaller electrochemical HOMO–LUMO gap (0.45 eV) than that of Ni(II) dimesitylnorcorrole (1.08 eV). Furthermore, the triply linked hybrid exhibits singlet diradical characteristics, as confirmed by VT NMR, ESR, and SQUID experiments.

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