Improved photocatalytic hydrogen evolution driven by chloro(terpyridine)platinum(II) derivatives tethered to a single pendant viologen acceptor
Improved photocatalytic hydrogen evolution driven by chloro(terpyridine)platinum(II) derivatives tethered to a single pendant viologen acceptor
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DOI：
10.1039/c6dt01456a
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发表时间：
2016-01-01
影响因子：
4
通讯作者：
Sakai, Ken
中科院分区：
文献类型：
--
作者：
Lin, Shu;Kitamoto, Kyoji;Sakai, Ken
三种氯（4 ′-（N-甲基吡啶鎓）-2，2 ′：6 ′，2 ″-三联吡啶）铂（II）（缩写为PtL 2+）衍生物，其与单个烷基紫精单元（-（CH 2）n-CH 2-N+ C5 H4-C5 H4 N +-CH 3;缩写为-Cn-MV 2+，其中n = 1、3和4）相连，i.例如，合成了PtL ~（2+）-Cn-MV ~（2+）配合物。结果表明，在牺牲电子给体EDTA（乙二胺四乙酸二钠盐）存在下，通过连接单个烷基MV 2+单元，从水中光催化放出H-2的转换数（TON）显著提高（TON = 21.5-25.2，12 h）。分光光度法研究表明，PtL ~（2+）-Cn-MV ~（2+）体系在EDTA存在下的光辐射首先导致1-电子还原物种的形成，然后导致2-电子还原物种的形成，其中光激发物种的还原猝灭是每个步骤中还原光产物的主要途径。电化学研究表明，PtL 2+单元的两个连续的1-电子还原与MV 2+单元的相应还原几乎重叠。因此，1-电子还原的物种可以表示为PtL+-Cn-MV ~（2+）或PtL ~（2+）-Cn-MV ~（2+），而2-电子还原的物种可以表示为PtL ~（2+）-Cn-MV ~（2+）。此外，后一种产物表现为涉及三种类型的P-二聚体位点（PtL+）（2）、（MV+）（2）和（PtL+）（MV+）的堆叠物质，并且根据以下反应不驱动热出：PtL+中心点-Cn-MV+中心点+2H（+）-> PtL（2+）Cn-MV 2 + + H-2。发现PtL ~（2+）-Cn-MV ~（2+）光催化水的析氢反应是通过形成3-电子还原物种进行的; PtL+中心点-Cn-MV+中心点+ EDTA + hnu-> PtL 0-Cn-MV+中心点（或PtL+中心点-Cn-MV 0）+ EDTA（ox），和PtL 0-Cn-MV+中心点（或PtL+中心点-Cn-MV 0）+2 H（+）-> PtL+中心点-Cn-MV 2+（或PtL 2 +-Cn-MV+中心点）+ H-2。
Three chloro(4'-(N-methylpyridinium)-2,2': 6', 2 ''-terpyridine) platinum(II) (abbreviated as PtL2+) derivatives tethered to a single alkyl viologen unit (-(CH2) n-CH2-N+C5H4-C5H4N+-CH3; abbreviated as -Cn-MV2+, where n = 1, 3, and 4), i. e., PtL2+-Cn-MV2+, have been synthesized and investigated in detail. It is shown that the turnover number (TON) for the photocatalytic H-2 evolution from water in the presence of a sacrificial electron donor EDTA (ethylenediaminetetraacetic acid disodium salt) is dramatically improved by the attachment of a single alkyl MV2+ unit (TON = 21.5-25.2, 12 h). Spectrophotometric studies reveal that the photoirradiation of PtL2+-Cn-MV2+ in the presence of EDTA initially leads to the formation of a 1-electron-reduced species, and then to a 2-electron-reduced species, where reductive quenching of a photoexcited species is a major path to the reduced photoproduct in each step. Electrochemical studies show that two consecutive 1-electron reductions at the PtL2+ unit are nearly overlapped with the corresponding reductions at the MV2+ unit. The 1-electron-reduced species can be thus expressed as either PtL+--Cn-MV2+ or PtL2+-Cn-MV+-, while the 2-electron-reduced one as PtL2+-Cn-MV+-. Moreover, the latter products behave as stacked species involving three types of p-dimer sites, (PtL+)(2), (MV+)(2), and (PtL+) (MV+), and do not drive thermal H2 evolution according to the reaction: PtL+center dot-Cn-MV+center dot + 2H(+) -> PtL(2+)Cn- MV2+ + H-2. The H-2 evolution from water photocatalyzed by PtL2+-Cn-MV2+ has been found to occur via formation of 3-electron-reduced species; PtL+center dot-Cn-MV+center dot + EDTA + h nu -> PtL0-Cn-MV+center dot (or PtL+center dot-Cn-MV0) + EDTA(ox), and PtL0-Cn-MV+center dot (or PtL+center dot-Cn-MV0) + 2H(+) -> PtL+center dot-Cn-MV2+ (or PtL2+-Cn-MV+center dot) + H-2.