Nihei Masayuki, Ida Hiromichi, Nibe Takayuki, Moeljadi Adhitya Mangala Putra, Trinh Quang Thang, Hirao Hajime, Ishizaki Manabu, Kurihara Masato, Shiga Takuya, Oshio Hiroki
Faculty of Pure and Applied Sciences, Department of Chemistry , University of Tsukuba , Tennodai 1-1-1 , Tsukuba 305-8571 , Japan.
Department of Chemistry , City University of Hong Kong , Tat Chee Avenue , Kowloon , Hong Kong , People's Republic of China.
J Am Chem Soc. 2018 Dec 19;140(50):17753-17759. doi: 10.1021/jacs.8b10957. Epub 2018 Dec 5.
Metal oxides with sizes of a few nanometers show variable crystal and electronic structures depending on their dimensions, and the synthesis of metal oxide particles with a desired size is a key technology in materials science. Although discrete metal oxide particles with an average diameter ( d) smaller than 2 nm are expected to show size-specific properties, such ultrasmall metal oxide particles are significantly limited in number. In nature, on the other hand, nanosized ferrihydrite (Fh), which is ferric oxyhydroxide, occurs as a result of biomineralization in ferritin, an iron storage protein cage. Here we describe the synthesis of Fh particles using a covalent molecular organic cage (MOC) derived from 8 + 12 cyclocondensation of triaminocyclohexane with a diformylphenol derivative. At the initial reaction stage, eight iron ions accumulated at the metal binding sites in the cage cavity, and Fh particles ( d = 1.9 ± 0.3 nm) encapsulated within the cage (Fh@MOC) formed with a quite narrow size distribution. The formation process of the Fh particle in the organic cage resembles the biomineralization process in the natural iron storage protein, and the present method could be applicable to the synthesis of other metal oxide particles. Fh@MOC is soluble in common organic solvents and shows substantial redox activity in MeCN.
尺寸为几纳米的金属氧化物因其尺寸不同而呈现出可变的晶体结构和电子结构，合成具有所需尺寸的金属氧化物颗粒是材料科学中的一项关键技术。尽管预计平均直径（d）小于2 nm的离散金属氧化物颗粒会表现出尺寸特异性性质，但这种超小金属氧化物颗粒的数量极为有限。另一方面，在自然界中，纳米尺寸的水铁矿（Fh），即氢氧化铁，是由铁储存蛋白笼铁蛋白中的生物矿化作用产生的。在此，我们描述了使用由三氨基环己烷与二甲醛苯酚衍生物进行8 + 12环缩合反应得到的共价分子有机笼（MOC）来合成Fh颗粒。在初始反应阶段，八个铁离子在笼腔中的金属结合位点积累，形成了包裹在笼内的Fh颗粒（d = 1.9 ± 0.3 nm）（Fh@MOC），其尺寸分布相当窄。有机笼中Fh颗粒的形成过程类似于天然铁储存蛋白中的生物矿化过程，并且本方法可能适用于合成其他金属氧化物颗粒。Fh@MOC可溶于常见有机溶剂，并在乙腈中表现出显著的氧化还原活性。
