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<p>Conjugated polypyrroles have attracted intensive attention due to their unique properties, and they have emerged as potential platforms for stabilizing radicals. With the purpose to construct stable polypyrrole radicals, a benzothiadiazole unit has been incorporated into a heptapyrrin framework to afford <b>1</b>. Thus, <b>1</b> exists as a singlet ground state diradical with a narrow singlet-triplet energy gap (Δ<i>E</i><sub>S-T</sub>) of −3.17 kcal mol<sup>−1</sup>. On this basis, <b>1</b> has been coordinated with Pd(II) and Ni(II) salts to afford binuclear complexes <b>1-Pd</b> and <b>1-Ni</b>. Notably, <b>1-Ni</b> retains the diradical character with a narrowed Δ<i>E</i><sub>S-T</sub> of −0.65 kcal mol<sup>−1</sup>, whereas <b>1-Pd</b> is a closed-shell species. As a result, <b>1, 1-Pd</b>, and <b>1-Ni</b> exhibit intense near-infrared-II (NIR-II) absorption bands at 1076, 1283, and 1309 nm, respectively, enabling them to function as NIR-II photothermal conversion materials. Thus, <b>1</b> and diradical species <b>1-Ni</b> show relatively high photothermal conversion efficiencies (<i>η</i>) of 37.6% and 38.6%, respectively. Whereas, closed-shell derivatives of <b>1</b> such as the oxidized (<b>1-ox</b>), reduced (<b>1-re</b>) and coordination (<b>1-Pd</b>) species exhibit lowered efficiencies of 24.8%, 26.5%, and 30.9%, respectively. These results provide insight into developing stable open-shell oligopyrroles as efficient photothermal materials, with the efficiencies further enhanced by coordination with transition metal ions while retaining the open-shell character.</p>

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Benzothiadiazole-containing heptapyrrin: modulation of diradical character and photothermal conversion via metal coordination

  • 期刊论文

  • 发表日期：

    2026年7月24日

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  • Zhen Yang,
  • Xiandong He,
  • Glib Baryshnikov,
  • Bin Zhu,
  • Chengjie Li,
  • Shijun Li,
  • Hans Ågren,
  • Qizhao Li,
  • Yongshu Xie,
  • Yuguang Ma

摘要

Conjugated polypyrroles have attracted intensive attention due to their unique properties, and they have emerged as potential platforms for stabilizing radicals. With the purpose to construct stable polypyrrole radicals, a benzothiadiazole unit has been incorporated into a heptapyrrin framework to afford 1. Thus, 1 exists as a singlet ground state diradical with a narrow singlet-triplet energy gap (ΔES-T) of −3.17 kcal mol−1. On this basis, 1 has been coordinated with Pd(II) and Ni(II) salts to afford binuclear complexes 1-Pd and 1-Ni. Notably, 1-Ni retains the diradical character with a narrowed ΔES-T of −0.65 kcal mol−1, whereas 1-Pd is a closed-shell species. As a result, 1, 1-Pd, and 1-Ni exhibit intense near-infrared-II (NIR-II) absorption bands at 1076, 1283, and 1309 nm, respectively, enabling them to function as NIR-II photothermal conversion materials. Thus, 1 and diradical species 1-Ni show relatively high photothermal conversion efficiencies (η) of 37.6% and 38.6%, respectively. Whereas, closed-shell derivatives of 1 such as the oxidized (1-ox), reduced (1-re) and coordination (1-Pd) species exhibit lowered efficiencies of 24.8%, 26.5%, and 30.9%, respectively. These results provide insight into developing stable open-shell oligopyrroles as efficient photothermal materials, with the efficiencies further enhanced by coordination with transition metal ions while retaining the open-shell character.