J Phys Chem A. 2022 Mar 10;126(9):1530-1541. doi: 10.1021/acs.jpca.2c00035. Epub 2022 Mar 1.
A boron dipyrromethene (BODIPY) derivative bearing a -proline residue at the -position crystallizes in the form of platelets with strong (i.e., Φ = 0.34) red fluorescence, but the absorption and emission spectra differ markedly from those for dilute solutions. A key building block for the crystal is a -dimer where hydrogen bonding aligns the proline groups and separates the terminal chromophores by ca. 25 Å. Comparison with a covalently linked bichromophore suggests that one-dimensional (1D) excitonic coupling between the terminals is too small to perturb the optical properties. However, accretion of the -dimer forms narrow channels possessing a high density of chromophores. The resultant absorption spectrum exhibits strong excitonic splitting, which can be explained quantitatively using the extended dipole approach and allowing for coupling between ca. 30 BODIPY units. Fluorescence, which decays with a lifetime of 2.2 ns, is assigned to a delocalized and (slightly) super-radiant BODIPY dimer situated at the interface and populated via electronic energy transfer from the interior.
一种带有 -脯氨酸残基的硼二吡咯甲川（BODIPY）衍生物在 -位置结晶成具有强（即 Φ = 0.34）红色荧光的片状物，但吸收和发射光谱与稀溶液显著不同。晶体的一个关键构建块是 -二聚体，其中氢键将脯氨酸基团对齐，并将末端发色团分离约 25 Å。与共价连接的双发色团的比较表明，末端之间的一维（1D）激子耦合太小，不会干扰光学性质。然而，-二聚体的积累形成了具有高发色团密度的狭窄通道。所得吸收光谱表现出强烈的激子分裂，可以使用扩展偶极子方法进行定量解释，并允许约 30 个 BODIPY 单元之间的耦合。荧光寿命为 2.2 ns，分配给位于界面处的离域和（略）超辐射 BODIPY 二聚体，并通过从内部进行的电子能量转移来填充。
