Malakar Partha, Borin Veniamin, Bedi Anjan, Schapiro Igor, Gidron Ori, Ruhman Sanford
Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem, Israel.
Fritz Haber Center for Molecular Dynamics, Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem, Israel.
Phys Chem Chem Phys. 2022 Jan 26;24(4):2357-2362. doi: 10.1039/d1cp05728f.
Due to their unique excited state dynamics, acenes play a dominant role in optoelectronic and light-harvesting applications. Their optical and electronic properties are typically tailored by side-group engineering, which often result in distortion of the acene core from planarity. However, the effect of such distortion on their excited state dynamics is not clear. In this work, we investigate the effect of twisting on the photophysics of acenes, which are helically locked to a defined twist angle by tethers of different lengths. Ultrafast transient absorption and time resolved fluorescence show a clear dependence of the rate of intersystem crossing with twisting. This trend is explained using quantum chemical calculations, showing an increase of spin-orbit coupling (SOC). At much earlier times, structural reorganization in S, including coherent vibrational wave packet motions, is reflected in transient spectral changes. As predicted by theory, decreasing the length of diagonal tether induces enhanced activity and frequency blue-shifting of a normal vibration consisting of anthracene twisting against restraint of the tethering chain. Overall, these results serve as design principles for tuning photophysical properties of acenes controlled twisting of their aromatic core.
由于其独特的激发态动力学，并苯在光电和光捕获应用中发挥着主导作用。它们的光学和电子性质通常通过侧基工程来调整，这往往会导致并苯核心从平面性发生扭曲。然而，这种扭曲对其激发态动力学的影响尚不清楚。在这项工作中，我们研究了扭曲对并苯光物理性质的影响，这些并苯通过不同长度的连接链螺旋锁定到特定的扭曲角度。超快瞬态吸收和时间分辨荧光表明，系间窜越速率与扭曲存在明显的相关性。利用量子化学计算解释了这一趋势，结果表明自旋轨道耦合（SOC）增加。在更早的时间，S态中的结构重组，包括相干振动波包运动，反映在瞬态光谱变化中。正如理论所预测的，减少对角连接链的长度会增强由蒽相对于连接链的约束进行扭曲所构成的正常振动的活性和频率蓝移。总体而言，这些结果为通过控制并苯芳香核的扭曲来调节其光物理性质提供了设计原则。
