Development of Aromaticity‐Tunable Meso ‐Edited Phthalocyanine Derivatives

Phthalocyanine derivatives exhibit excellent photophysical properties, including strong absorption and emission in the visible‐to‐near‐infrared (NIR) regions, and have found a broad range of applications in material and life sciences. However, the limitations of reported synthetic methods restrict the available structural diversity and variety of electronic structures, in marked contrast with the diverse structural chemistry of porphyrin analogues. Here, we report the synthesis, characterization, and electronic properties of various transition metal complexes of meso ‐edited phthalocyanine derivatives, i.e., tetrabenzodiazacorroles 3 and tetrabenzotriazacorroles 4 . These meso ‐edited compounds were obtained via deprotonative macrocyclization of open‐form phthalonitrile tetramer‐metal complexes 2 , and exhibit different electronic characters depending on the central metals. Divalent metals such as Ni(II), Pd(II), and Pt(II) afford stable 17π‐electron tetrabenzoazacorrole radicals 3 and 4 with broad NIR‐II and NIR‐III absorption, while trivalent Rh(III) yields 16π‐electron antiaromatic macrocycle 3aRh and 18π‐electron aromatic macrocycle 3bRh . The 17π‐electron radicals undergo redox reactions to generate 16π‐antiaromatic and 18π‐aromatic species, accompanied with pronounced spectral changes in red‐to‐NIR absorption and phosphorescence. These radical‐based and antiaromatic phthalocyanine derivatives offer a promising platform for applications requiring versatile on/off‐switchable NIR emission capability.