酶的外部配位层可微调活性位点的反应性并控制催化速率,这表明将类似的结构元素掺入分子催化剂中可能是必需的,以达到与在低超电势下在酶系统中观察到的速率相当的速率。在这项工作中,我们评估了氨基酸和二肽外配位球对[Ni(P Ph 2 N Ph-R 2)2 ] 2+产氢催化剂的影响。制备了一系列包含非天然氨基酸或二肽的12种新配合物,以测试位置,大小,极性和芳香性对催化活性的影响。非天然氨基酸要么3-(间-或对氨基苯丙酸丙酸以酸,酯或酰胺终止。二肽由非天然氨基酸之一与四种氨基酸酯之一组成:丙氨酸,丝氨酸,苯丙氨酸或酪氨酸。所有催化剂都对产氢具有活性,平均速率约为1000 s -1,比未改性的催化剂快40%。C末端肽的脂族或芳族侧链的结构和极性不会强烈影响速率。然而,酰胺键的存在增加了速率,表明酰胺在辅助催化中的作用。在N-苯基间位带有取代基的超电势较低。这与较不紧凑,对等的电子传输较慢相一致。-取代
Incorporating Peptides in the Outer-Coordination Sphere of Bioinspired Electrocatalysts for Hydrogen Production
摘要:
Four new cyclic 1,5-diaza-3,7-diphosphacyclooctane ligands have been prepared and used to synthesize [Ni(p(2)(ph)N(2)(R))(2)](2+) complexes in which R is a mono- or dipeptide. These complexes represent a first step in the development of an outer-coordination sphere for this class of complexes that can mimic the outer-coordination sphere of the active sites of hydrogenase enzymes. Importantly, these complexes retain the electrocatalytic activity of the parent [Ni((P2N2Ph)-N-Ph)(2)](2+) complex in an acetonitrile solution with turnover frequencies for hydrogen production ranging from 14 to 25 s(-1) in the presence of p-cyanoaniliniurn trifluoromethanesulfonate and from 135 to 1000 s(-1) in the presence of protonated dimethylformamide, with moderately low overpotentials, similar to 0.3 V. The addition of small amounts of water results in rate increases of 2-7 times. Unlike the parent complex, these complexes demonstrate dynamic structural transformations in solution. These results establish a building block from which larger peptide scaffolding can be added to allow the [Ni(p(2)(R)N(2)(R'))(2)](2+) molecular catalytic core to begin to mimic the multifunctional outer-coordination sphere of enzymes.
opposite‐charged DuBois‐Ni catalysts. The hot electrons of photoexcited BENI‐COO− nanofibers were tunneled to the molecular Ni collectors across a salt bridge and an alkyl region of 2.2–2.5 nm length at a rate of 6.10×108 s−1, which is five times larger than the BENI‐NH3+ nanoribbons (1.17×108 s−1). The electricfield benefited significantly the electrontunneling dynamics and compensated the charge‐separated
Electrocatalytic Oxidation of Formate with Nickel Diphosphine Dipeptide Complexes: Effect of Ligands Modified with Amino Acids
作者:Brandon R. Galan、Matthew L. Reback、Avijita Jain、Aaron M. Appel、Wendy J. Shaw
DOI:10.1002/ejic.201300751
日期:2013.10.14
A series of nickel bis-diphosphine complexes with dipeptides appended to the ligands were investigated for the catalytic oxidation of formate. Typical rates of ~7 s-1 were found, similar to the parent complex (~8 s-1), with aminoacid size and positioning contributing very little to rate or operating potential. Hydroxyl functionalities did result in lower rates, which were recovered by protecting the
A Hydrogen-Evolving Ni(P<sub>2</sub>N<sub>2</sub>)<sub>2</sub> Electrocatalyst Covalently Attached to a Glassy Carbon Electrode: Preparation, Characterization, and Catalysis. Comparisons with the Homogeneous Analogue
作者:Atanu K. Das、Mark H. Engelhard、R. Morris Bullock、John A. S. Roberts
DOI:10.1021/ic500701a
日期:2014.7.7
A hydrogen-evolving homogeneous Ni(P2N2)2 electrocatalyst with peripheral ester groups has been covalentlyattached to a 1,2,3-triazolyllithium-terminated planar glassy carbon electrode surface. Coupling proceeds with both the Ni(0) and the Ni(II) complexes. X-ray photoemission spectra show excellent agreement between the Ni(0) coupling product and its parent complex, and voltammetry of the surface-confined
具有外围酯基的放氢均相Ni(P 2 N 2)2电催化剂已共价连接至以1,2,3-三唑基锂为末端的平面玻璃碳电极表面。Ni(0)和Ni(II)配合物都进行偶联。X射线光发射光谱表明Ni(0)偶联产物与其母体之间有极好的一致性,表面受限系统的伏安法表明,单一物质占优势,表面密度为1.3×10 –10 mol cm –2,接近密集包装的单层的估算值。使用Ni(II)系统时,光发射和伏安数据均显示出偶合时未鉴定产物的形态,其表面密度为6.7×10 –11 mol cm –2。表面受限的Ni(0)络合物是析氢的电催化剂,显示出与可溶母体络合物处于相同电位的催化电流的开始。在酸性乙腈中观察到了表面受限物质的分解。这被解释为反映了Ni(II)-膦相互作用的不稳定性和游离膦的碱性,并且还涉及同时实施表面受限的Ni(P 2 N 2)2的努力。 电化学或光电化学装置中的配合物。