Brezinski William P, Karayilan Metin, Clary Kayla E, McCleary-Petersen Keelee C, Fu Liye, Matyjaszewski Krzysztof, Evans Dennis H, Lichtenberger Dennis L, Glass Richard S, Pyun Jeffrey
Department of Chemistry and Biochemistry, The University of Arizona, 1306 East University Blvd, Tucson, Arizona 85721, United States.
Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 151213, United States.
ACS Macro Lett. 2018 Nov 20;7(11):1383-1387. doi: 10.1021/acsmacrolett.8b00765. Epub 2018 Nov 8.
Small-molecule catalysts inspired by the active sites of [FeFe]-hydrogenase enzymes have long struggled to achieve fast rates of hydrogen evolution, long-term stability, water solubility, and oxygen compatibility. We profoundly improved on these deficiencies by grafting polymers from a metalloinitiator containing a [2Fe-2S] moiety to form water-soluble poly(2-dimethylamino)ethyl methacrylate metallopolymers () using atom transfer radical polymerization (ATRP). This study illustrates the critical role of the polymer composition in enhancing hydrogen evolution and aerobic stability by comparing the catalytic activity of with a nonionic water-soluble metallopolymer based on poly(oligo(ethylene glycol) methacrylate) prepared via ATRP () with the same [2Fe-2S] metalloinitiator. Additionally, the tunability of catalyst activity is demonstrated by the synthesis of metallocopolymers incorporating the 2-(dimethylamino)ethyl methacrylate (DMAEMA) and oligo(ethylene glycol) methacrylate (OEGMA) monomers. Electrochemical investigations into these metallo(co)polymers show that retains complete aerobic stability with catalytic current densities in excess of 20 mA·cm, while fails to reach 1 mA·cm current density even with the application of high overpotentials (η > 0.8 V) and loses all activity in the presence of oxygen. Random copolymers of the two monomers polymerized with the same [2Fe-2S] initiator showed intermediate activity in terms of current density, overpotential, and aerobic stability.
长期以来，受[FeFe]-氢化酶活性位点启发的小分子催化剂一直难以实现快速析氢、长期稳定性、水溶性和与氧的兼容性。我们通过原子转移自由基聚合（ATRP），从含有[2Fe-2S]部分的金属引发剂接枝聚合物，以形成水溶性聚（甲基丙烯酸2-二甲基氨基乙酯）金属聚合物（），从而显著改善了这些不足。本研究通过比较与基于聚（甲基丙烯酸寡聚（乙二醇）酯）的非离子水溶性金属聚合物（）在相同[2Fe-2S]金属引发剂下通过ATRP制备的催化活性，阐明了聚合物组成在增强析氢和有氧稳定性方面的关键作用。此外，通过合成包含甲基丙烯酸2-（二甲基氨基）乙酯（DMAEMA）和甲基丙烯酸寡聚（乙二醇）酯（OEGMA）单体的金属共聚物，证明了催化剂活性的可调性。对这些金属（共）聚合物的电化学研究表明，在催化电流密度超过20 mA·cm时，仍保持完全的有氧稳定性，而即使施加高过电位（η>0.8 V），也未能达到1 mA·cm的电流密度，并且在有氧存在下失去所有活性。用相同[2Fe-2S]引发剂聚合的两种单体的无规共聚物在电流密度、过电位和有氧稳定性方面表现出中等活性。
