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。
The Role of a Dipeptide Outer-Coordination Sphere on H<sub>2</sub>-Production Catalysts: Influence on Catalytic Rates and Electron Transfer
作者:Matthew L. Reback、Bojana Ginovska-Pangovska、Ming-Hsun Ho、Avijita Jain、Thomas C. Squier、Simone Raugei、John A. S. Roberts、Wendy J. Shaw
DOI:10.1002/chem.201202849
日期:2013.2.4
presence of an amidebond increases rates, suggesting a role for the amide in assisting catalysis. Overpotentials were lower with substituents at the N‐phenyl meta position. This is consistent with slower electron transfer in the less compact, para‐substituted complexes, as shown in digital simulations of catalyst cyclic voltammograms and computational modeling of the complexes. Combining the current
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
作者:Avijita Jain、Sheri Lense、John C. Linehan、Simone Raugei、Herman Cho、Daniel L. DuBois、Wendy J. Shaw
DOI:10.1021/ic1025872
日期:2011.5.2
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.