Department of Chemistry and Pharmacy, Interdisciplinary Center for Molecular Materials (ICMM), Friedrich-Alexander-Universität Erlangen-Nuernberg, Egerlandstr. 3, 91058, Erlangen, Germany.
Department of Chemistry, University of Crete, Laboratory of Bioinorganic Chemistry, Voutes Campus, 71003, Heraklion, Crete, Greece.
Chemphyschem. 2019 Nov 5;20(21):2806-2815. doi: 10.1002/cphc.201900780. Epub 2019 Oct 14.
A study on electron transfer in three electron donor-acceptor complexes is reported. These architectures consist of a zinc phthalocyanine (ZnPc) as the excited-state electron donor and a fullerene (C ) as the ground-state electron acceptor. These complexes are brought together by axial coordination at ZnPc. The key variable in our design is the length of the molecular spacer, namely, oligo-p-phenylenevinylenes. The lack of appreciable ground-state interactions is in accordance with strong excited-state interactions, as inferred from the quenching of ZnPc centered fluorescence and the presence of a short-lived fluorescence component. Full-fledged femtosecond and nanosecond transient absorption spectroscopy assays corroborated that the ZnPc ⋅ -C ⋅ charge-separated state formation comes at the expense of excited-state interactions following ZnPc photoexcitation. At a first glance, the ZnPc ⋅ -C ⋅ charge-separated state lifetime increased from 0.4 to 86.6 ns as the electron donor-acceptor separation increased from 8.8 to 29.1 Å. A closer look at the kinetics revealed that the changes in charge-separated state lifetime are tied to a decrease in the electronic coupling element from 132 to 1.2 cm , an increase in the reorganization energy of charge transfer from 0.43 to 0.63 eV, and a large attenuation factor of 0.27 Å .
报道了三个电子给体-受体配合物中电子转移的研究。这些结构由锌酞菁（ZnPc）作为激发态电子给体和富勒烯（C ）作为基态电子受体组成。这些配合物通过 ZnPc 上的轴向配位结合在一起。我们设计中的关键变量是分子间隔物的长度，即寡聚对苯乙烯基乙烯。从 ZnPc 中心荧光的猝灭和短寿命荧光组分的存在可以推断出，缺乏明显的基态相互作用与强激发态相互作用是一致的。充分的飞秒和纳秒瞬态吸收光谱分析证实，ZnPc- -C- -电荷分离态的形成是以 ZnPc 光激发后激发态相互作用为代价的。乍一看，随着电子给体-受体分离从 8.8 埃增加到 29.1 埃，ZnPc- -C- -电荷分离态的寿命从 0.4 纳秒增加到 86.6 纳秒。更仔细地观察动力学表明，电荷分离态寿命的变化与电子耦合元件从 132 厘米降至 1.2 厘米、电荷转移的重组能从 0.43 电子伏特增加到 0.63 电子伏特以及衰减因子 0.27 埃的大幅降低有关。
