Ultrafast dynamics in the power stroke of a molecular rotary motor
Ultrafast dynamics in the power stroke of a molecular rotary motor
复制标题
DOI：
10.1038/nchem.1343
复制
发表时间：
2012-07-01
期刊：
影响因子：
21.8
通讯作者：
Meech, Stephen R.
中科院分区：
文献类型：
--
作者：
Conyard, Jamie;Addison, Kiri;Meech, Stephen R.
光驱动的分子马达通过激发态反应将光转化为机械能。基于手性过度拥挤的烯烃的单向旋转分子马达通过连续的光化学和热步骤工作。通过分子结构的变化，热(螺旋反转)步骤已经成功地进行了优化，但对为马达提供动力的光化学步骤却知之甚少。最终，控制分子马达的效率需要对激发态势能面上的分子动力学有一个详细的描述。在这里，我们使用时间分辨率低于50ps的超快荧光上转换测量来表征单向分子马达吸收光子后的初级事件。我们在Franck-Condon区域观察到一个非常快的初始弛豫，这意味着一个无障碍的反应坐标。这种快速的分子运动伴随着相干激发态结构运动的激发。这些观察结果对操纵电机效率的意义进行了讨论。
Light-driven molecular motors convert light into mechanical energy through excited-state reactions. Unidirectional rotary molecular motors based on chiral overcrowded alkenes operate through consecutive photochemical and thermal steps. The thermal (helix inverting) step has been optimized successfully through variations in molecular structure, but much less is known about the photochemical step, which provides power to the motor. Ultimately, controlling the efficiency of molecular motors requires a detailed picture of the molecular dynamics on the excited-state potential energy surface. Here, we characterize the primary events that follow photon absorption by a unidirectional molecular motor using ultrafast fluorescence up-conversion measurements with sub 50 fs time resolution. We observe an extraordinarily fast initial relaxation out of the Franck-Condon region that suggests a barrierless reaction coordinate. This fast molecular motion is shown to be accompanied by the excitation of coherent excited-state structural motion. The implications of these observations for manipulating motor efficiency are discussed.