Praneeth Vijayendran K K, Kondo Mio, Okamura Masaya, Akai Takuya, Izu Hitoshi, Masaoka Shigeyuki
Department of Life and Coordination-Complex Molecular Science , Institute for Molecular Science (IMS) , 5-1 Higashiyama, Myodaiji , Okazaki , Aichi 444-8787 , Japan . Email:
SOKENDAI [The Graduate University for Advanced Studies] , Shonan Village , Hayama , Kanagawa 240-0193 , Japan.
Chem Sci. 2019 Mar 19;10(17):4628-4639. doi: 10.1039/c9sc00678h. eCollection 2019 May 7.
The development of robust and efficient molecular catalysts based on earth-abundant transition metals for water oxidation reactions is a challenging research target. Our group recently demonstrated the high activity and stability of a pentairon-based water oxidation electrocatalyst (M. Okamura, M. Kondo, R. Kuga, Y. Kurashige, T. Yanai, S. Hayami, V. K. K. Praneeth, M. Yoshida, K. Yoneda, S. Kawata and S. Masaoka, , 2016, , 465-468). However, the development of strategies to decrease onset potentials for catalysis remains challenging. In this article, we report the construction of a series of pentanuclear iron complexes by introducing electron-donating (methyl) and electron-withdrawing (bromo) substituents on the ligand. Two newly synthesized complexes exhibited five reversible redox processes, similar to what is seen with the parent complex. These complexes can also serve as homogeneous catalysts for water oxidation reactions, and the faradaic efficiencies of the reactions were high. Additionally, the onset potentials of the newly developed complexes were lower than that of the parent complex. Mechanistic insights revealed that there are two methods for decreasing onset potentials: control of the redox potentials of the pentairon complex and control of the reaction mechanism.
开发基于储量丰富的过渡金属的用于水氧化反应的强大且高效的分子催化剂是一个具有挑战性的研究目标。我们小组最近证明了一种基于五铁的水氧化电催化剂具有高活性和稳定性（冈村真、近藤正、久贺良、仓重洋、柳井隆、速水涉、普拉内斯·V·K·K、吉田正、米田康、川田幸、政冈伸，《化学通讯》，2016年，第52卷，第465 - 468页）。然而，开发降低催化起始电位的策略仍然具有挑战性。在本文中，我们报告了通过在配体上引入供电子（甲基）和吸电子（溴）取代基来构建一系列五核铁配合物。两个新合成的配合物表现出五个可逆的氧化还原过程，这与母体配合物的情况相似。这些配合物还可以作为水氧化反应的均相催化剂，并且反应的法拉第效率很高。此外，新开发的配合物的起始电位低于母体配合物。机理研究表明，有两种降低起始电位的方法：控制五铁配合物的氧化还原电位和控制反应机理。
