Ultrafast Exciton Delocalization, Localization and Excimer Formation Dynamics in a Highly Defined Perylene Bisimide Quadruple π-Stack,Journal of the American Chemical Society

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Ultrafast Exciton Delocalization, Localization and Excimer Formation Dynamics in a Highly Defined Perylene Bisimide Quadruple π-Stack
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2018-03-05 , DOI: 10.1021/jacs.7b11571
Christina Kaufmann ₁ , Woojae Kim ₂ , Agnieszka Nowak-Król ₁ , Yongseok Hong ₂ , Dongho Kim ₂ , Frank Würthner ₁

Affiliation

An adequately designed, bay-tethered perylene bisimide (PBI) dimer Bis-PBI was synthesized by Pd/Cu-catalyzed Glaser-type oxidative homocoupling of the respective PBI building block. This newly synthesized PBI dimer self-assembles exclusively and with high binding constants of up to 106 M-1 into a discrete π-stack of four chromophores. Steady-state absorption and emission spectra show the signatures of H-type excitonic coupling among the dye units. Broadband fluorescence upconversion spectroscopy (FLUPS) reveals an ultrafast dynamics in the optically excited state. An initially coherent Frenkel exciton state that is delocalized over the whole quadruple stack rapidly (τ = ∼200 fs) loses its coherence and relaxes into an excimer state. Comparison with Frenkel exciton dynamics in PBI dimeric and oligomeric H-aggregates demonstrates that in the quadruple stack coherent exciton propagation is absent due to its short length of aggregates, thereby it has only one relaxation pathway to the excimer state. Furthermore, the absence of pump-power dependence in transient absorption experiments suggests that multiexciton cannot be generated in the quadruple stack, which is in line with time-resolved fluorescence measurements.

中文翻译：

高度定义的苝双酰亚胺四重 π 堆栈中的超快激子离域、定位和准分子形成动力学

通过相应 PBI 结构单元的 Pd/Cu 催化的 Glaser 型氧化均偶联，合成了一种设计合理的、由海湾连接的苝双酰亚胺 (PBI) 二聚体 Bis-PBI。这种新合成的 PBI 二聚体以高达 106 M-1 的高结合常数自组装成四个发色团的离散 π 堆栈。稳态吸收和发射光谱显示了染料单元之间 H 型激子耦合的特征。宽带荧光上转换光谱 (FLUPS) 揭示了光激发态的超快动力学。最初相干的弗伦克尔激子态在整个四重堆栈上迅速离域（τ = ∼200 fs），失去相干性并弛豫成准分子态。与 PBI 二聚体和寡聚体 H 聚集体中的 Frenkel 激子动力学的比较表明，在四重堆叠中，由于聚集体的长度较短，相干激子传播不存在，因此它只有一个弛豫途径到准分子态。此外，瞬态吸收实验中不存在泵浦功率依赖性表明不能在四重堆栈中产生多激子，这与时间分辨荧光测量一致。

更新日期：2018-03-05

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