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首页> 外文OA文献 >Computational Study of Fluorinated Diglyoxime-Iron Complexes: Tuning the Electrocatalytic Pathways for Hydrogen Evolution
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Computational Study of Fluorinated Diglyoxime-Iron Complexes: Tuning the Electrocatalytic Pathways for Hydrogen Evolution

机译：含氟二氧肟肟-铁配合物的计算研究：调节氢析出的电催化途径

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The ability to tune the properties of hydrogen-evolving molecular electrocatalysts is important for developing alternative energy sources. Fluorinated diglyoxime-iron complexes have been shown to evolve hydrogen at moderate overpotentials. Herein two such complexes, [(dAr^FgBF_2)_2Fe(py)_2], denoted A, and [(dAr^Fg_2H-BF_2)Fe(py)_2], denoted B [dAr^Fg = bis(pentafluorophenyl-glyoximato); py = pyridine], are investigated with density functional theory calculations. B differs from A in that one BF_2 bridge is replaced by a proton bridge of the form O–H–O. According to the calculations, the catalytic pathway for A involves two consecutive reduction steps, followed by protonation of an Fe^0 species to generate the active Fe^(II)-hydride species. B is found to proceed via two parallel pathways, where one pathway is similar to that for A, and the additional pathway arises from protonation of the O–H–O bridge, followed by spontaneous reduction to an Fe^0 intermediate and intramolecular proton transfer from the ligand to the metal center or protonation by external acid to form the same active Fe^(II)-hydride species. Simulated cyclic voltammograms (CVs) based on these mechanisms are in qualitative agreement with experimental CVs. The two parallel pathways identified for B arise from an equilibrium between the protonated and unprotonated ligand and result in two catalytic peaks in the CVs. The calculations predict that the relative probabilities for the two pathways, and therefore the relative magnitudes of the catalytic peaks, could be tuned by altering the pK_a of the acid or the substituents on the ligands of the electrocatalyst. The ability to control the catalytic pathways through acid strength or ligand substituents is critical for designing more effective catalysts for energy conversion processes.
机译：调节析氢分子电催化剂性能的能力对于开发替代能源非常重要。氟化二氧肟肟-铁络合物已显示出在中等超电势下释放出氢气。在此，两个这样的络合物，表示为A的[（dAr ^ FgBF_2）_2Fe（py）_2]，和表示为B的[（dAr ^ Fg_2H-BF_2）Fe（py）_2]，[dAr ^ Fg =双（五氟苯基-乙二氧基）。 ; py =吡啶]，用密度泛函理论计算进行研究。 B与A的不同之处在于，一个BF_2桥被形式为O–H–O的质子桥取代。根据计算，A的催化途径涉及两个连续的还原步骤，然后使Fe ^ 0物质质子化以生成活性Fe ^（II）-氢化物物质。发现B通过两个平行的途径进行，其中一个途径与A相似，另外的途径来自O–H–O桥的质子化，然后自发还原为Fe ^ 0中间分子和分子内质子转移从配体到金属中心或通过外部酸质子化以形成相同的活性Fe ^（II）-氢化物。基于这些机制的模拟循环伏安图（CV）与实验CV的定性一致。 B的两个平行途径来自质子化和未质子化配体之间的平衡，并在CV中产生两个催化峰。该计算预测，可以通过改变酸的pK_a或电催化剂的配体上的取代基来调节两种途径的相对概率，从而催化峰的相对幅度。通过酸强度或配体取代基控制催化途径的能力对于设计用于能量转化过程的更有效的催化剂至关重要。

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