Department of Chemistry & Biology, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3, Canada.
Department of Chemistry, Durham University, Lower Mountjoy, Stockton Road, Durham DH1 3LE, United Kingdom.
Inorg Chem. 2020 Sep 21;59(18):13533-13541. doi: 10.1021/acs.inorgchem.0c01891. Epub 2020 Aug 30.
Porphyrins are cornerstone functional materials that are useful in a wide variety of settings, ranging from molecular electronics to biology and medicine. Their applications are often hindered, however, by poor solubilities that result from their extended, solvophobic aromatic surfaces. Attempts to counteract this problem by functionalizing their peripheries have been met with only limited success. Here, we demonstrate a versatile strategy to tune the physical and electronic properties of porphyrins using an axial functionalization approach. Porphyrin silanes (PorSils) and bissilyloxy PorSils (SOPS) are prepared from porphyrins by operationally simple κ-silylation protocols, introducing bulky silyloxy "caps" that are central and perpendicular to the planar porphyrin. While porphyrins typically form either J- or H-aggregates, SOPS do not self-associate in the same manner: the silyloxy axial substituents dramatically improve the solubility by inhibiting aggregation. Moreover, axial porphyrin functionalization offers convenient handles through which optical, electronic, and structural properties of the porphyrin core can be modulated. We observe that the identity of the silyloxy substituent impacts the degree of planarity of the porphyrin in the solid state as well as the redox potentials.
卟啉是基石功能材料，在从分子电子学到生物学和医学等各种环境中都有应用。然而，由于其扩展的、疏溶剂性的芳香表面，它们的溶解度很差，这限制了它们的应用。通过官能团化其外围来解决这个问题的尝试，仅取得了有限的成功。在这里，我们展示了一种使用轴向官能化方法来调整卟啉物理和电子性质的通用策略。通过操作简单的κ-硅烷基化方案，从卟啉制备卟啉硅烷（PorSils）和双硅烷氧基 PorSils（SOPS），引入了体积庞大的硅氧基“帽”，它们位于平面卟啉的中心并垂直于该平面。虽然卟啉通常形成 J-或 H-聚集体，但 SOPS 不会以相同的方式自组装：硅氧基轴向取代基通过抑制聚集极大地提高了溶解度。此外，轴向卟啉官能化提供了方便的处理手段，可以调节卟啉核心的光学、电子和结构性质。我们观察到，硅氧基取代基的性质会影响卟啉在固态中的平面度以及氧化还原电位。
