Universität Würzburg, Institut für Organische Chemie and Center for Nanosystems Chemistry, Am Hubland, 97074 Würzburg, Germany.
Chemistry. 2012 Jun 4;18(23):7060-70. doi: 10.1002/chem.201200089. Epub 2012 Apr 30.
Herein we report on structural, morphological, and optical properties of homochiral and heterochiral J-aggregates that were created by nucleation-elongation assembly of atropo-enantiomerically pure and racemic perylene bisimides (PBIs), respectively. Our detailed studies with conformationally stable biphenoxy-bridged chiral PBIs by UV/Vis absorption, circular dichroism (CD) spectroscopy, and atomic force microscopy (AFM) revealed structurally as well as spectroscopically quite different kinds of J-aggregates for enantiomerically pure and racemic PBIs. AFM investigations showed that enantiopure PBIs form helical nanowires of unique diameter and large length-to-width ratio by self-recognition, while racemic PBIs provide irregular-sized particles by self-discrimination of the enantiomers at the stage of nucleation. Steady-state fluorescence spectroscopy studies revealed that the photoluminescence efficiency of homochiral J-aggregated nanowires (47±3%) is significantly higher than that of heterochiral J-aggregated particle-like aggregates (12±3%), which is explained in terms of highly ordered molecular stacking in one-dimensional nanowires of homochiral J-aggregates. Our present results demonstrate the high impact of homochirality on the construction of well-defined nanostructures with unique optical properties.
在此，我们报告了由对映体纯和外消旋的苝二酰亚胺（PBI）分别通过成核-延伸组装形成的同手性和异手性 J 聚集体的结构、形态和光学性质。我们通过紫外/可见吸收、圆二色性（CD）光谱和原子力显微镜（AFM）对构象稳定的联苯氧基桥联手性 PBI 进行了详细研究，揭示了对映体纯和外消旋 PBI 的 J 聚集体在结构和光谱上都具有非常不同的种类。AFM 研究表明，对映体纯 PBI 通过自识别形成独特直径和大长径比的螺旋纳米线，而外消旋 PBI 通过在成核阶段对映体的自分辨提供不规则尺寸的颗粒。稳态荧光光谱研究表明，同手性 J 聚集纳米线（47±3%）的荧光效率明显高于异手性 J 聚集颗粒状聚集体（12±3%），这可以用同手性 J 聚集纳米线中一维分子堆积的高度有序来解释。我们目前的结果表明，手性对构建具有独特光学性质的明确定义的纳米结构具有重大影响。
