Synthesis and Characterization of Quinone Compounds Derived from Doubly- and Triply-Linked Diporphyrins and Tuning of Their Absorption Properties

Porphyrins are attracting increasing attention in materials science and photochemistry owing to their unique properties and diverse applications. This study focuses on modifying and tuning the absorption properties of porphyrins, specifically those of quinoidal porphyrins, to extend their spectral range into the near-infrared (NIR) region. We report the synthesis and structural and physical properties of quinone compounds derived from doubly- and triply-linked diporphyrins and their metal complexes. Doubly-linked diporphyrinquinone exhibits broad panchromatic absorption properties in solution owing to its low symmetry. Metal complexation markedly extends its absorption range to the near-infrared region. In contrast, the metal complexes of the triply-linked diporphyrinquinones exhibit sharp and strong absorption bands in the visible to near-infrared region owing to their higher symmetry. The longest absorption wavelength of the triply-linked diporphyrinquinones was approximately 1500 nm, which was significantly more red-shifted than that of the doubly-linked ones.