Modeling electronic excitation of bacteriochlorophyll (BChl) molecules in light-harvesting (LH) antennae from photosynthetic centers presents a challenge for the quantum theory. We report on a quantum chemical study of the ring of 32 BChl molecules from the bacterial core complex LH1-RC. Diagonal and off-diagonal elements of the excitonic Hamiltonian matrices are estimated in quantum chemical calculations of relevant fragments using the TD-DFT and CIS approaches. The deviation of the computed excitation energy of this BChl system from the experimental data related to the Q_y band maximum of this LH1-RC complex is about 0.2 eV. We demonstrate that corrections due to improvement in modeling of an individual BChl molecule and due to contributions from the protein environment are in the range of the obtained discrepancy between theory and experiment. Differences between results of the excitonic model and direct quantum chemical calculations of BChl aggregates fall in the same range.

从光合作用中心对光收集（LH）触角中细菌叶绿素（BChl）分子的电子激发进行建模对量子理论提出了挑战。我们报告了从细菌核心复合体LH1-RC的32个BChl分子的环的量子化学研究。使用TD-DFT和CIS方法在相关片段的量子化学计算中估计了激子哈密顿矩阵的对角和非对角元素。该BChl系统的计算出的激发能与与Q _y相关的实验数据的偏差该LH1-RC络合物的最大带最大约为0.2 eV。我们证明，由于对单个BChl分子的建模改进和由于蛋白质环境的贡献而引起的校正，在理论与实验之间获得的差异范围内。激子模型结果与BChl团聚体的直接量子化学计算之间的差异落在同一范围内。