Photoinitiated multi-step charge separation and ultrafast charge transfer induced dissociation in a pyridyl-linked photosensitizer-cobaloxime assembly
Photoinitiated multi-step charge separation and ultrafast charge transfer induced dissociation in a pyridyl-linked photosensitizer-cobaloxime assembly
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DOI：
10.1039/c3ee40378e
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发表时间：
2013-06-01
影响因子：
32.5
通讯作者：
Wasielewski, Michael R.
中科院分区：
文献类型：
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作者：
Veldkamp, Brad S.;Han, Won-Sik;Wasielewski, Michael R.
使用可见光和近红外瞬态吸收光谱来跟踪不同的激发态、阳离子和阴离子信号，我们报告了自组装供体-桥-受体-钴肟三元组中光引发多步电荷分离和超快电荷转移诱导解离的详细动力学分析。供体-桥-受体配体由通过二甲苯桥连接至吡啶基取代的1,8-萘二甲酰亚胺电子受体的苝发色团组成。配体与催化剂[Co(dmgBF(2))(2)(L)(2)]的配位，其中dmgBF(2) - (二氟硼基)二甲基乙肟和L水或溶剂分子，产生供体-桥-受体-催化剂三元组组件。 416 nm 激光脉冲的光激发产生苝 S-1 激发态。随后电子从苝转移到受体的时间为 tau = 9.0 +/- 0.1 ps，随后电子转移到催化剂的时间为 tau = 6 +/- 1 ps。在形成的电荷分离态群中，79 +/- 1% 经历电荷重组至单重基态 (tau = 0.8 +/- 0.1 ns) 或苝三重态 (tau = 4.3 +/- 0.1 ns)。 tau = 2.4 +/- 0.2 ns 的 Co(I)-吡啶基键解离与分子内电荷重组竞争，导致解离的氧化光敏剂和还原催化剂的产率为 21 +/- 1%。随后发生扩散电荷复合，时间为 k = (1.8 +/- 0.2) x 10(10) M-1 s(-1)。对集成光敏剂-催化剂系统的电子转移和解离动力学的详细分析将为有效吸收光子、转移电子和催化燃料形成反应的新型分子组件的合理设计提供信息。
Using visible and near-infrared transient absorption spectroscopy to track distinct excited state, cation, and anion signals, we report a detailed kinetic analysis of photoinitiated multi-step charge separation and ultrafast charge transfer induced dissociation in a self-assembled donor-bridge-acceptor-cobaloxime triad. The donor-bridge-acceptor ligand consists of a perylene chromophore linked via a xylene bridge to a pyridyl-substituted 1,8-naphthalimide electron acceptor. Coordination of the ligand to the catalyst [Co(dmgBF(2))(2)(L)(2)], where dmgBF(2) - (difluoroboryl) dimethylglyoximato and L water or a solvent molecule, yields a donor-bridge-acceptor-catalyst triad assembly. Photoexcitation with 416 nm laser pulses generates the perylene S-1 excited state. Subsequent electron transfer from perylene to the acceptor occurs in tau = 9.0 +/- 0.1 ps followed by electron transfer to the catalyst in tau = 6 +/- 1 ps. Of the charge-separated state population formed, 79 +/- 1% undergoes charge recombination to either the singlet ground state (tau = 0.8 +/- 0.1 ns) or the perylene triplet state (tau = 4.3 +/- 0.1 ns). Co(I)-pyridyl bond dissociation with tau = 2.4 +/- 0.2 ns competes with intramolecular charge recombination resulting in a 21 +/- 1% yield of dissociated oxidized photosensitizer and reduced catalyst. Subsequent diffusional charge recombination occurs with k = (1.8 +/- 0.2) x 10(10) M-1 s(-1). This detailed analysis of the electron transfer and dissociation dynamics of an integrated photosensitizer-catalyst system will inform the rational design of novel molecular assemblies that efficiently absorb photons, transfer electrons, and catalyze fuel-forming reactions.