Photoinduced electron transfer in a molecular dyad by nanosecond pump–pump–probe spectroscopy†,Photochemical & Photobiological Sciences

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Photoinduced electron transfer in a molecular dyad by nanosecond pump–pump–probe spectroscopy†
Photochemical & Photobiological Sciences ( IF 2.7 ) Pub Date : 2018-05-14 00:00:00 , DOI: 10.1039/c8pp00048d
M.-H. Ha-Thi _{1,

2,

3,

4,

5} , V.-T. Pham _{1,

2,

3,

4,

5} , T. Pino _{1,

2,

3,

4,

5} , V. Maslova _{1,

2,

3,

4,

5} , A. Quaranta _{6,

7,

8,

9,

10} , C. Lefumeux _{1,

2,

3,

4,

5} , W. Leibl _{6,

7,

8,

9,

10} , A. Aukauloo _{6,

7,

8,

9,

10}

Affiliation

The design of robust and inexpensive molecular photocatalysts for the conversion of abundant stable molecules like H₂O and CO₂ into an energetic carrier is one of the major fundamental questions for scientists nowadays. The outstanding challenge is to couple single photoinduced charge separation events with the sequential accumulation of redox equivalents at the catalytic unit for performing multielectronic catalytic reactions. Herein, double excitation by nanosecond pump–pump–probe experiments was used to interrogate the photoinduced charge transfer and charge accumulation on a molecular dyad composed of a porphyrin chromophore and a ruthenium-based catalyst in the presence of a reversible electron acceptor. An accumulative charge transfer state is unattainable because of rapid reverse electron transfer to the photosensitizer upon the second excitation and the low driving force of the forward photodriven electron transfer reaction. Such a method allows the fundamental understanding of the relaxation mechanism after two sequential photon absorptions, deciphering the undesired electron transfer reactions that limit the charge accumulation efficiency. This study is a step toward the improvement of synthetic strategies of molecular photocatalysts for light-induced charge accumulation and more generally, for solar energy conversion.

中文翻译：

纳秒级泵浦-泵浦-探针光谱法在分子二倍体中的光诱导电子转移†

设计坚固耐用且价格便宜的分子光催化剂，以转化丰富的稳定分子，例如H ₂ O和CO ₂成为精力充沛的载体是当今科学家的主要基本问题之一。突出的挑战是将单个光诱导的电荷分离事件与催化单元上氧化还原当量的顺序积累耦合起来，以进行多电子催化反应。在此，通过纳秒级泵浦-泵浦-探针实验的双重激励，在可逆电子受体存在的情况下，对由卟啉发色团和钌基催化剂组成的分子二倍体上的光诱导电荷转移和电荷积聚进行了询问。由于在第二次激发时正向电子快速反向转移至光敏剂，并且正向光驱动电子转移反应的驱动力较低，因此无法获得累积的电荷转移状态。这种方法允许对两个连续的光子吸收后的弛豫机理有基本的了解，从而破译了限制电荷积累效率的不良电子转移反应。这项研究是朝着改进分子光催化剂的合成策略迈出的一步，该策略用于光诱导的电荷积累，更广泛地来说，是用于太阳能转换。

更新日期：2018-05-14

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