标题： 巨大π共轭轮辐状大环中的激子局域化波动 显示英文标题

标题： Fluctuating exciton localisation in giant pi-conjugated spoked-wheel macrocycles

摘要： 共轭聚合物在许多不同的应用中具有潜力，但我们仍然缺乏对其电子结构的基本微观理解。 基本的光激发——激子——仅跨越分子的几个纳米，而分子本身可以延伸到微米级别，它们的行为如何受到分子尺寸的影响尚不完全清楚。 例如，在共轭片段内部激子是如何形成的，它是否总是位于相同的重复单元上？ 在此，我们引入了结构刚性分子轮辐结构，直径为6纳米，作为扩展π共轭的模型。 单分子荧光显示激子的随机定位，导致发射偏振的时间变化。 最初，这种随机定位是由于温度无关的自发对称性破缺，每次光子吸收事件后都会发生。 在长时间照射后，这些快速波动减缓到毫秒时间尺度。 通过低温光谱学揭示了分子内异质性，表现为跃迁能量的跳跃，然而，发射偏振也可以在没有光谱跳跃的情况下切换，这意味着局部介电环境具有长程均一性。 显示英文摘要

摘要： Conjugated polymers offer potential for many diverse applications but we still lack a fundamental microscopic understanding of their electronic structure. Elementary photoexcitations - excitons - span only a few nanometres of a molecule, which itself can extend over microns, and how their behaviour is affected by molecular dimensions is not fully understood. For example, where is the exciton formed within a conjugated segment, is it always situated on the same repeat units? Here, we introduce structurally-rigid molecular spoked wheels, 6 nanometres in diameter, as a model of extended pi-conjugation. Single-molecule fluorescence reveals random exciton localisation, leading to temporally-varying emission polarisation. Initially, this random localisation arises after every photon absorption event because of temperature independent spontaneous symmetry breaking. These fast fluctuations are slowed to millisecond timescales following prolonged illumination. Intramolecular heterogeneity is revealed in cryogenic spectroscopy by jumps in transition energy, however, emission polarisation can also switch without a spectral jump occurring, implying long-range homogeneity in local dielectric environment.