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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Photochemical and thermal hydrogen production from water catalyzed by carboxylate-bridged dirhodium(ii) complexes
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Photochemical and thermal hydrogen production from water catalyzed by carboxylate-bridged dirhodium(ii) complexes

机译：羧酸桥联的ho（ii）配合物催化的水的光化学和热产氢

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A series of dinuclear Rh(ii) complexes, [Rh_2(μ-OAc) _4(H_2O)_2] (HOAc = acetic acid) (1), [Rh _2(μ-gly)_4(H_2O)_2] (Hgly = glycolic acid) (2), [Rh_2(μ-CF_3CO_2) _4(acetone)_2] (3), and [Rh_2(bpy) _2(μ-OAc)_2(OAc)_2] (4), were found to serve as H_2-evolving catalysts in a three-component system consisting of tris(2,2′-bipyridine)ruthenium(ii) (Ru(bpy)_3~(2+)), methylviologen (MV~(2+)), and ethylenediaminetetraacetic acid disodium salt (EDTA). It was also confirmed that thermal reduction of water into H _2 by MV~+, in situ generated by the bulk electrolysis of MV~(2+), is effectively promoted by 1 as a H_2-evolving catalyst. The absorption spectra of the photolysis solution during the photocatalysis were monitored up to 6 h to reveal that the formation of photochemical or thermal byproducts of MV~+ is dramatically retarded in the presence of the Rh(ii)_2 catalysts, for the H_2 formation rather than the decomposition of MV~+ becomes predominant in the presence of the Rh(ii)_2 catalysts. The stability of the Rh(ii)_2 dimers was confirmed by absorption spectroscopy, ~1H NMR, and ESI-TOF mass spectroscopy. The results indicated that neither elimination nor replacement of the equatorial ligands take place during the photolysis, revealing that one of the axial sites of the Rh_2 core is responsible for the hydrogenic activation. The quenching of Ru*(bpy)_3~(2+) by 1 was also investigated by luminescence spectroscopy. The rate of H_2 evolution was found to decrease upon increasing the concentration of 1, indicating that the quenching of Ru*(bpy)_3~(2+) by the Rh(ii)_2 species rather than by MV~(2+) becomes predominant at the higher concentrations of 1. The DFT calculations were carried out for several possible reaction paths proposed (e.g., [Rh~(II)_2(μ-OAc)_4(H _2O)] + H~+ and [Rh~(II)_2(μ-OAc) _4(H_2O)] + H~+ + e~-). It is suggested that the initial step is a proton-coupled electron transfer (PCET) to the Rh(ii)_2 dimer leading to the formation of a Rh(ii)Rh(iii)-H intermediate. The H_2 evolution step is suggested to proceed either via the transfer of another set of H~+ and e~- to the Rh(ii)Rh(iii)-H intermediate or via the homolytic radical coupling through the interaction of two Rh(ii)Rh(iii)-H intermediates.
机译：一系列双核Rh（ii）配合物[Rh_2（μ-OAc）_4（H_2O）_2]（HOAc =乙酸）（1），[Rh _2（μ-gly）_4（H_2O）_2]（Hgly =羟基乙酸（2），[Rh_2（μ-CF_3CO_2）_4（丙酮）_2]（3）和[Rh_2（bpy）_2（μ-OAc）_2（OAc）_2]（4）被发现起作用在由三（2,2'-联吡啶）钌（ii）（Ru（bpy）_3〜（2+）），甲基紫精（MV〜（2+））和三组分组成的三组分体系中作为H_2演化催化剂乙二胺四乙酸二钠盐（EDTA）。还证实了由MV〜（2+）的整体电解原位产生的MV〜+将水热还原为H _2被1作为促进H_2的催化剂有效地促进了。监测光催化过程中光解溶液的吸收光谱长达6小时，发现在Rh（ii）_2催化剂存在下，MV〜+的光化学副产物或热副产物的形成显着受阻，对于H_2的形成在Rh（ii）_2催化剂的存在下，MV〜+的分解变得尤为重要。 Rh（ii）_2二聚体的稳定性已通过吸收光谱，〜1H NMR和ESI-TOF质谱证实。结果表明，在光解过程中，既没有消除也没有置换出赤道配体，这表明Rh_2核的轴向位点之一是氢活化的原因。还通过发光光谱研究了Ru *（bpy）_3〜（2+）被1猝灭的现象。发现随着浓度1的增加，H_2的释放速率降低，这表明通过Rh（ii）_2而不是MV〜（2+）对Ru *（bpy）_3〜（2+）的猝灭变为主要在较高浓度的1下进行。针对所提出的几种可能的反应路径（例如[Rh〜（II）_2（μ-OAc）_4（H _2O）] + H〜+和[Rh〜（ II）_2（μ-OAc）_4（H_2O）] + H〜+ + e〜-）。建议的初始步骤是质子偶联电子转移（PCET）到Rh（ii）_2二聚体，导致形成Rh（ii）Rh（iii）-H中间体。建议通过另一组H〜+和e〜-转移至Rh（ii）Rh（iii）-H中间体或通过两个Rh（ii ）Rh（iii）-H中间体。

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