Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States.
Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
J Am Chem Soc. 2021 Jan 20;143(2):1098-1106. doi: 10.1021/jacs.0c11895. Epub 2020 Dec 30.
We assembled eight cofacial porphyrin prisms using MTPyP (M = Co(II) or Zn(II), TPyP = 4-tetrapyridylporphyrin) and functionalized ruthenium-based "molecular clips" using coordination-driven self-assembly. Our approach allows for the rapid synthesis of these architectures in isolated yields as high as 98% for the assembly step. Structural and reactivity studies provided a deeper understanding of the role of the building blocks on the oxygen reduction reaction (ORR). Catalytic efficacy was probed by using cyclic and hydrodynamic voltammetry on heterogeneous catalyst inks in aqueous media. The reported prisms showed outstanding selectivity (>98%) for the kinetically hindered 4e/4H reduction of O to HO over the kinetically more accessible 2e/2H reduction to HO. Furthermore, we have demonstrated significant cofacial enhancement in the observed catalytic rate constant (∼5 orders of magnitude) over the mononuclear analogue. We conclude that the steric bulk of the clip plays an important role in the structural dynamics of these prisms, which in turn modulates the ORR reactivity with respect to selectivity and kinetics.
我们使用 MTPyP（M = Co(II) 或 Zn(II)，TPyP = 4-四吡啶基卟啉）和功能化基于钌的“分子夹”通过配位驱动的自组装组装了八个共面卟啉棱柱体。我们的方法允许在孤立产率下快速合成这些结构，组装步骤的产率高达 98%。结构和反应性研究深入了解了构建块对氧还原反应（ORR）的作用。通过在水介质中的异相催化剂油墨上使用循环伏安法和动电伏安法来探测催化功效。报道的棱柱体显示出对动力学受阻的 4e/4H 将 O 还原为 HO 的出色选择性（>98%），而动力学上更易接近的 2e/2H 还原为 HO 的选择性（>98%）。此外，我们已经证明了在观察到的催化速率常数（∼5 个数量级）方面相对于单核类似物具有显著的共面增强。我们得出结论，夹的空间位阻在这些棱柱体的结构动力学中起着重要作用，这反过来又调节了 ORR 反应的选择性和动力学。
