Identification of a new electron-transfer relaxation pathway in photoexcited pyrrole dimers.
Identification of a new electron-transfer relaxation pathway in photoexcited pyrrole dimers.
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DOI：
10.1038/ncomms11357
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发表时间：
2016-04-21
影响因子：
16.6
通讯作者：
Fielding HH
中科院分区：
文献类型：
--
作者：
Neville SP;Kirkby OM;Kaltsoyannis N;Worth GA;Fielding HH
光诱导电子转移是许多生物过程和技术应用的核心，例如太阳能和分子电子学的收集。参与电子转移的电子供体和受体单元通常通过共价键、π-π相互作用或氢键固定到位。在这里，利用时间分辨光电子能谱和从头计算，我们揭示了由 NH⋯π 键结合在一起的分子中存在一种新的、低能量的光诱导电子转移机制。具体来说，我们捕获了吡咯二聚体中的电子转移过程，从供体吡咯的激发 π 系统到位于受体吡咯 N 原子上的里德伯轨道，这是由受体分子上的 N-H 拉伸介导的。由此产生的电荷转移状态的寿命令人惊讶，并导致有效的电子弛豫。我们认为这种松弛途径在含有吡咯构件的生物和技术系统中发挥着重要作用。 通过吡咯部分以及吡咯部分之间的光诱导电子转移是自然世界和新兴技术中的重要过程。在这里，作者利用实验和理论计算来研究吡咯二聚体中先前未被发现的弛豫途径。
Photoinduced electron transfer is central to many biological processes and technological applications, such as the harvesting of solar energy and molecular electronics. The electron donor and acceptor units involved in electron transfer are often held in place by covalent bonds, π–π interactions or hydrogen bonds. Here, using time-resolved photoelectron spectroscopy and ab initio calculations, we reveal the existence of a new, low-energy, photoinduced electron-transfer mechanism in molecules held together by an NH⋯π bond. Specifically, we capture the electron-transfer process in a pyrrole dimer, from the excited π-system of the donor pyrrole to a Rydberg orbital localized on the N-atom of the acceptor pyrrole, mediated by an N–H stretch on the acceptor molecule. The resulting charge-transfer state is surprisingly long lived and leads to efficient electronic relaxation. We propose that this relaxation pathway plays an important role in biological and technological systems containing the pyrrole building block. Photoinduced electron transfer through, and between, pyrrole moieties is an important process both in the natural world and emerging technologies. Here, the authors use both experiment and theoretical calculation to investigate a previously undiscovered relaxation pathway arising in pyrrole dimers.