A Quantum Chemical Interpretation of Two-Dimensional Electronic Spectroscopy of Light-Harvesting Complexes
A Quantum Chemical Interpretation of Two-Dimensional Electronic Spectroscopy of Light-Harvesting Complexes
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DOI：
10.1021/jacs.7b02130
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发表时间：
2017-06-07
影响因子：
15
通讯作者：
Mennucci, Benedetta
中科院分区：
文献类型：
--
作者：
Segatta, Francesco;Cupellini, Lorenzo;Mennucci, Benedetta
非线性电子光谱是研究复杂多发色团结构的最有力的技术之一。事实上，对于这些系统，线性光谱太拥挤，不能用来解开许多耦合的振动电子过程被激活。相反，通过使用2D方法，可以实现清晰的图像，但只有当记录的光谱与适当的解释模型相结合时。到目前为止，这几乎总是通过参数化激子哈密顿量来实现的，这必然会引入偏见和/或任意假设。在这项研究中，第一性原理的方法，结合了准确的量子化学描述与国家的最先进的环境模型，通过使用原子和极化嵌入。缓慢和快速浴动力学，沿着与激子之间的颜料运输，包括在内。该方法被应用到紫色细菌的光捕获2（LH 2）复合物的2DES光谱。模拟扩展到整个可见近红外光谱区域，以涵盖类胡萝卜素和细菌叶绿素信号。我们的研究结果提供了一个精确的描述激子的性质和弛豫途径，并给出了前所未有的洞察到测量的二维信号的光谱特征的解释。
Nonlinear electronic spectroscopies represent one of the most powerful techniques to study complex multichromophoric architectures. For these systems, in fact, linear spectra are too congested to be used to disentangle the many coupled vibroelectronic processes that are activated. By using a 2D approach, instead, a clear picture can be achieved, but only when the recorded spectra are combined with a proper interpretative model. So far, this has been almost always achieved through parametrized exciton Hamiltonians that necessarily introduce biases and/or arbitrary assumptions. In this study, a first-principles approach is presented that combines accurate quantum chemical descriptions with state-of-the-art models for the environment through the use of atomistic and polarizable embeddings. Slow and fast bath dynamics, along with exciton transport between the pigments, are included. This approach is applied to the 2DES spectroscopy of the Light-Harvesting 2 (LH2) complex of purple bacteria. Simulations are extended over the entire visible-near-infrared spectral region to cover both carotenoid and bacteriochlorophyll signals. Our results provide an accurate description of excitonic properties and relaxation pathways, and give an unprecedented insight into the interpretation of the spectral signatures of the measured 2D signals.