圆二色光谱的视觉理解：相互作用发色团的情形

中文摘要 AI 辅助

激子耦合塑造了分子聚集体的光物理和手性光学性质，但关于分子间相互作用如何产生圆二色（CD）的微观实空间理解仍不完整。在此，我们通过计算研究耦合分子二聚体中CD的微观起源，以区分分子间（拓扑）手性与分子内（固有）手性。时间依赖密度泛函理论与跃迁手性张量（TCT）分析的结合提供了一个定量、视觉直观的框架，展示了电子耦合强度、分子间距离和相对角度取向如何控制手性光学响应。我们发现，成对的单个非手性发色团表现出稳健的拓扑手性光学信号，这些信号产生常规的Cotton效应，这是圆二色光谱中导数特征的标准解释。接下来我们确定，固有手性发色团由于固有手性与拓扑手性之间的竞争而破坏Cotton效应。这项工作为使用TCT方法解释分子聚集体、超分子组装体和纳米结构中的激子耦合CD光谱奠定了基础，该方法为分析与新兴量子技术相关的复杂多发色团系统中的手性光学响应提供了有吸引力的工具。

英文摘要

Exciton coupling shapes the photophysical and chiroptical properties of molecular aggregates, but a microscopic, real-space understanding of how intermolecular interactions generate circular dichroism (CD) remains incomplete. Here, we computationally investigate the microscopic origins of CD in coupled molecular dimers to separate intermolecular (topological) from intramolecular (intrinsic) chirality. A combination of time-dependent density functional theory and transition chiral tensor (TCT) analysis provides a quantitative, visually intuitive framework showing how electronic coupling strength, intermolecular separation, and relative angular orientation govern chiroptical response. We find that pairs of individually achiral chromophores exhibit robust, topological chiroptical signals which give rise to the conventional Cotton effect, a standard interpretation of derivative features in circular dichroism spectra. We next establish that intrinsically chiral chromophores, on the other hand, disrupt the Cotton effect due to the competition between intrinsic chirality and topological chirality. This work establishes a foundation for interpreting exciton-coupled CD spectra in molecular aggregates, supramolecular assemblies, and nanostructures using the TCT approach, which offers an attractive tool for analyzing chiroptical responses in complex multi-chromophore systems relevant to emerging quantum technologies.

发表机构

• Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室）

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