Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, USA.
J Am Chem Soc. 2011 Jul 27;133(29):11289-98. doi: 10.1021/ja202898p. Epub 2011 Jun 29.
The dynamics of negative polaron and triplet exciton transport within a series of monodisperse platinum (Pt) acetylide oligomers is reported. The oligomers consist of Pt-acetylide repeats, PtL(2)-C≡C-Ph-C≡C- (where L = PBu(3) and Ph = 1,4-phenylene, n = 2, 3, 6, and 10), capped with naphthalene diimide (NDI) end groups. The Pt-acetylide segments are electro- and photoactive, and they serve as conduits for transport of electrons (negative polaron) and triplet excitons. The NDI end groups are relatively strong acceptors, serving as traps for the carriers. Negative polaron transport is studied by using pulse radiolysis/transient absorption at the Brookhaven National Laboratory Laser-Electron Accelerator Facility (LEAF). Electrons are rapidly attached to the oligomers, with some fraction initially residing upon the Pt-acetylide chains. The dynamics of transport are resolved by monitoring the spectral changes associated with transfer of electrons from the chain to the NDI end group. Triplet exciton transport is studied by femtosecond-picosecond transient absorption spectroscopy. Near-UV excitation leads to rapid production of triplet excitons localized on the Pt-acetylide chains. The excitons transport to the chain ends, where they are annihilated by charge separation with the NDI end group. The dynamics of triplet transport are resolved by transient absorption spectroscopy, taking advantage of the changes in spectra associated with decay of the triplet exciton and rise of the charge-separated state. The results indicate that negative polarons and excitons are transported rapidly, on average moving distances of ~3 nm in less than 200 ps. Analysis of the dynamics suggests diffusive transport by a site-to-site hopping mechanism with hopping times of ~27 ps for triplets and <10 ps for electrons.
报道了一系列单分散的铂（Pt）炔烃低聚物中，双负离子和三重态激子输运的动力学。这些低聚物由 Pt-炔键重复单元组成，PtL(2)-C≡C-Ph-C≡C-（其中 L = PBu(3)，Ph = 1,4-亚苯基，n = 2,3,6 和 10），两端用萘二酰亚胺（NDI）封端。Pt-炔键段是电子和光电活性的，它们作为电子（双负离子）和三重态激子传输的导体。NDI 端基是相对较强的受体，作为载体的陷阱。通过布鲁克海文国家实验室激光电子加速器设施（LEAF）的脉冲辐射/瞬态吸收研究双负离子输运。电子迅速与低聚物结合，其中一部分最初存在于 Pt-炔键链上。通过监测与电子从链转移到 NDI 端基相关的光谱变化，解析输运的动力学。通过飞秒-皮秒瞬态吸收光谱研究三重态激子输运。近紫外激发导致三重态激子快速产生，定域在 Pt-炔键链上。激子输运到链端，在那里与 NDI 端基发生电荷分离而被湮灭。通过瞬态吸收光谱解析三重态输运的动力学，利用与三重态激子衰减和电荷分离态上升相关的光谱变化。结果表明，双负离子和激子能够快速输运，平均在不到 200 ps 内移动约 3nm 的距离。动力学分析表明，通过站点到站点的跳跃机制进行扩散输运，三重态的跳跃时间约为 27 ps，电子的跳跃时间<10 ps。
