Coupling to Charge Transfer States is the Key to Modulate the Optical Bands for Efficient Light Harvesting in Purple Bacteria,The Journal of Physical Chemistry Letters

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Coupling to Charge Transfer States is the Key to Modulate the Optical Bands for Efficient Light Harvesting in Purple Bacteria
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2018-11-19 00:00:00 , DOI: 10.1021/acs.jpclett.8b03233
Lorenzo Cupellini ₁ , Stefano Caprasecca ₁ , Ciro A. Guido ₁ , Frank Müh ₂ , Thomas Renger ₂ , Benedetta Mennucci ₁

Affiliation

The photosynthetic apparatus of purple bacteria uses exciton delocalization and static disorder to modulate the position and broadening of its absorption bands, leading to efficient light harvesting. Its main antenna complex, LH2, contains two rings of identical bacteriochlorophyll pigments, B800 and B850, absorbing at 800 and 850 nm, respectively. It has been an unsolved problem why static disorder of the strongly coupled B850 ring is several times larger than that of the B800 ring. Here we show that mixing between excitons and charge transfer states in the B850 ring is responsible for the effect. The linear absorption spectrum of the LH2 system is simulated by using a multiscale approach with an exciton Hamiltonian generalized to include the charge transfer states that involve adjacent pigment pairs, with static disorder modeled microscopically by molecular dynamics simulations. Our results show that sufficient inhomogeneous broadening of the B850 band, needed for efficient light harvesting, is only obtained by utilizing static disorder in the coupling between local excited and interpigment charge transfer states.

中文翻译：

耦合到电荷转移状态是调制紫细菌中有效光收集光带的关键

紫色细菌的光合作用装置利用激子离域和静态无序来调节其吸收带的位置和宽度，从而实现有效的光收集。它的主要天线复合体LH2包含两个相同的细菌叶绿素色素环B800和B850，分别在800和850 nm处吸收。为什么强耦合的B850环的静态失常比B800环的静态失常大几倍，这是一个尚未解决的问题。在这里，我们证明了激子和B850环中电荷转移状态之间的混合是造成这种效应的原因。LH2系统的线性吸收光谱是通过使用多尺度方法模拟的，其中激子哈密顿量被概括为包括涉及相邻颜料对的电荷转移状态，通过分子动力学模拟在微观上模拟了静态障碍。我们的结果表明，只有通过在局部激发和颜料间电荷转移态之间的耦合中利用静态无序，才能获得有效的光收集所需的B850谱带的足够不均匀加宽。

更新日期：2018-11-19

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