Institute of Applied Mechanics, National Taiwan University, Taipei 106, Taiwan.
J Am Chem Soc. 2012 Sep 5;134(35):14279-82. doi: 10.1021/ja3047848. Epub 2012 Aug 22.
Nonplanar chiral aromatic molecules are candidates for use as building blocks of multidimensional switching devices because the π electrons can generate ring currents with a variety of directions. We employed (P)-2,2'-biphenol because four patterns of π-electron rotations along the two phenol rings are possible and theoretically determine how quantum switching of the π-electron rotations can be realized. We found that each rotational pattern can be driven by a coherent excitation of two electronic states under two conditions: one is the symmetry of the electronic states and the other is their relative phase. On the basis of the results of quantum dynamics simulations, we propose a quantum control method for sequential switching among the four rotational patterns that can be performed by using ultrashort overlapped pump and dump pulses with properly selected relative phases and photon polarization directions. The results serve as a theoretical basis for the design of confined ultrafast switching of ring currents of nonplanar molecules and further current-induced magnetic fluxes of more sophisticated systems.
非平面手性芳香分子是构建多维开关器件的候选材料，因为π电子可以产生具有多种方向的环电流。我们采用了（P）-2,2'-联苯酚，因为两个苯酚环上的π电子旋转有四种模式，并且从理论上确定了如何实现π电子旋转的量子开关。我们发现，在两种条件下，两种电子态的相干激发可以驱动每种旋转模式：一种是电子态的对称性，另一种是它们的相对相位。基于量子动力学模拟的结果，我们提出了一种量子控制方法，用于通过使用具有适当选择的相对相位和光子偏振方向的超短重叠泵浦和排空脉冲，在四个旋转模式之间进行顺序切换。这些结果为设计受限超快非平面分子环电流和更复杂系统的电流诱导磁通量的开关提供了理论基础。
