Excitation Energy Transfer in Bias-Free Dendrimers: Eigenstate Structure, Thermodynamics, and Quantum Evolution
Excitation Energy Transfer in Bias-Free Dendrimers: Eigenstate Structure, Thermodynamics, and Quantum Evolution
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DOI：
10.1021/acs.jpcc.2c02460
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发表时间：
2022-06
期刊：
影响因子：
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通讯作者：
Reshmi Dani;N. Makri
中科院分区：
文献类型：
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作者：
Reshmi Dani;N. Makri
我们使用矩阵对角化结合实时路径积分的方法来研究电子本征态和激子振动动力学的模型树枝状大分子与Frenkel激子之间的相互作用相邻的片段，其特征在于共轭分子组成的结构。即使在电子哈密顿量中没有明确的能量梯度的情况下，激子耦合也会通过本征态层次结构产生一个漏斗，将激发能从外围拉走。本征态结构和熵的考虑之间的竞争决定了平衡分布，这在小的树枝状聚合物在低温下倾向于有利于核心，随着树枝状聚合物的尺寸和热能的增加而向外移动，尽管这种分布可以通过增加同一代的片段之间的激子耦合而向核心偏斜。在高温下，分布变得经典，所有激发段具有相同的人口。强激子-振动耦合也使平衡分布向经典方向移动。我们发现，激发能量转移的动力学是高度非平凡的，强烈的量子力学效应的影响。一个积极的值的代内耦合（不管的符号的代间耦合参数）介绍了一个非常缓慢的组件的动态，我们归因于电子挫折。激子耦合，振动重组能和热能的大小大致相同，能量转移动力学的特征在于跨越2个数量级的时间尺度。丰富的动力学，结果从一个单参数的电子哈密顿提出了众多的设计可能性的树枝状结构与所需的功能。
We use matrix diagonalization in combination with real-time path integral methods to investigate the electronic eigenstates and exciton–vibration dynamics of model dendrimers with Frenkel exciton interactions between adjacent segments, which characterize structures composed of conjugated molecules. Even in the absence of an explicit energetic gradient in the electronic Hamiltonian, exciton couplings create a funnel through the eigenstate hierarchy that pulls the excitation energy away from the periphery. The competition between eigenstate structure and entropic considerations dictates the equilibrium distribution, which in small dendrimers at low temperatures tends to favor the core, shifting outward with increasing dendrimer size and thermal energy, although this distribution can be skewed back toward the core by increasing the exciton coupling between segments of the same generation. At high temperatures the distribution becomes classical, with all excited segments having the same population. Strong exciton–vibration coupling also shifts the equilibrium distribution in the classical direction. We find that the dynamics of excitation energy transfer is highly nontrivial and strongly affected by quantum mechanical effects. A positive value of the intrageneration coupling (regardless of the sign of the intergeneration coupling parameter) introduces a very slow component to the dynamics, which we attribute to electronic frustration. With exciton coupling, vibrational reorganization energy and thermal energy of approximately the same magnitude, the energy transfer dynamics is characterized by time scales that span 2 orders of magnitude. The rich dynamics that results from a single-parameter electronic Hamiltonian suggests a multitude of design possibilities for dendrimeric structures with a desirable function.