Ngo Thien H, Zieba David, Webre Whitney A, Lim Gary N, Karr Paul A, Kord Scheghajegh, Jin Shangbin, Ariga Katsuhiko, Galli Marzia, Goldup Steve, Hill Jonathan P, D'Souza Francis
International Center for Young Scientist (ICYS), National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki, 305-0044, Japan.
WPI Center for Materials Nanoarchitectonics, National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki, 305-0044 (Japan.
Chemistry. 2016 Jan 22;22(4):1301-12. doi: 10.1002/chem.201503490. Epub 2015 Nov 30.
An electron-deficient copper(III) corrole was utilized for the construction of donor-acceptor conjugates with zinc(II) porphyrin (ZnP) as a singlet excited state electron donor, and the occurrence of photoinduced charge separation was demonstrated by using transient pump-probe spectroscopic techniques. In these conjugates, the number of copper corrole units was varied from 1 to 2 or 4 units while maintaining a single ZnP entity to observe the effect of corrole multiplicity in facilitating the charge-separation process. The conjugates and control compounds were electrochemically and spectroelectrochemically characterized. Computational studies revealed ground state geometries of the compounds and the electron-deficient nature of the copper(III) corrole. An energy level diagram was established to predict the photochemical events by using optical, emission, electrochemical, and computational data. The occurrence of charge separation from singlet excited zinc porphyrin and charge recombination to yield directly the ground state species were evident from the diagram. Femtosecond transient absorption spectroscopy studies provided spectral evidence of charge separation in the form of the zinc porphyrin radical cation and copper(II) corrole species as products. Rates of charge separation in the conjugates were found to be of the order of 10(10) s(-1) and increased with increasing multiplicity of copper(III) corrole entities. The present study demonstrates the importance of copper(III) corrole as an electron acceptor in building model photosynthetic systems.
利用缺电子的铜（III）咕啉构建供体-受体共轭物，以锌（II）卟啉（ZnP）作为单重激发态电子供体，并通过瞬态泵浦-探测光谱技术证明了光诱导电荷分离的发生。在这些共轭物中，铜咕啉单元的数量从1个变化到2个或4个单元，同时保持单个ZnP实体，以观察咕啉多重性对促进电荷分离过程的影响。对共轭物和对照化合物进行了电化学和光谱电化学表征。计算研究揭示了化合物的基态几何结构以及铜（III）咕啉的缺电子性质。利用光学、发射、电化学和计算数据建立了能级图，以预测光化学事件。从该图中可以明显看出，单重激发态锌卟啉发生电荷分离，电荷复合直接产生基态物种。飞秒瞬态吸收光谱研究提供了电荷分离的光谱证据，其形式为锌卟啉自由基阳离子和铜（II）咕啉物种作为产物。发现共轭物中的电荷分离速率约为10(10) s(-1)，并随着铜（III）咕啉实体多重性的增加而增加。本研究证明了铜（III）咕啉作为电子受体在构建模型光合系统中的重要性。
