Department of Chemistry, St. Stephen's College, Uzhavoor P.O. Box 686634, Kerala, India.
Department of Applied Chemistry, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University, 1-1 Minami-Ohsawa Hachioji, Tokyo 192-0397, Japan.
Molecules. 2023 Feb 16;28(4):1882. doi: 10.3390/molecules28041882.
Faced with the new stage of water oxidation by molecular catalysts (MCs) in artificial photosynthesis to overcome the bottle neck issue, the "Photon-flux density problem of sunlight," a two-electron oxidation process forming HO in place of the conventional four-electron oxidation evolving O has attracted much attention. The molecular characteristics of tin(IV)-tetrapyridylporphyrin (SnTPyP), as one of the most promising MCs for the two-electron water oxidation, has been studied in detail. The protolytic equilibria among nine species of SnTPyP, with eight p values on the axial ligands' water molecules and peripheral pyridyl nitrogen atoms in both the ground and excited states, have been clarified through the measurements of UV-vis, fluorescence, H NMR, and dynamic fluorescence decay behaviour. The oxidation potentials in the Pourbaix diagram and spin densities by DFT calculation of the one-electron oxidized form of each nine species have predicted that the fully deprotonated species ([SnTPyP(O)]) and the singly deprotonated one ([SnTPyP(OH)(O)]) serve as the most favourable MCs for visible light-induced two-electron water oxidation when they are adsorbed on TiO for H formation or SnO for Z-scheme CO reduction in the molecular catalyst sensitized system of artificial photosynthesis.
面对人工光合作用中分子催化剂（MCs）对水氧化的新阶段，以克服瓶颈问题，“太阳光的光通量密度问题”，即形成 HO 的两电子氧化过程取代了传统的四电子氧化，释放 O 引起了广泛关注。锡（IV）-四吡咯啉卟啉（SnTPyP）作为最有前途的两电子水氧化 MCs 之一，其分子特性已被详细研究。通过测量 UV-vis、荧光、H NMR 和动态荧光衰减行为，阐明了 SnTPyP 在基态和激发态下轴向配体水分子和外围吡啶氮原子上的 8 个 p 值的九种 SnTPyP 物种的质子平衡和光解平衡。在 Pourbaix 图中的氧化电位和 DFT 计算的每种九种物种的一电子氧化形式的自旋密度预测，当它们吸附在 TiO 上用于 H 形成或 SnO 用于 Z 方案 CO 还原时，完全去质子化物种 ([SnTPyP(O)]) 和单去质子化物种 ([SnTPyP(OH)(O)]) 作为可见光诱导两电子水氧化的最有利的 MCs 在人工光合作用的分子催化剂敏化体系中。
