Kekulé Insitute of Organic Chemistry and Biochemistry, Rheinische-Friedrich-Wilhelms-University of Bonn, Gerhard-Domagk-Str. 1, D-53121, Bonn, Germany.
Energy and Semiconductor Research Laboratory, Institute of Physics, Carl-von-Ossietzky-University of Oldenburg, Carl-von-Ossietzky-Str. 9-11, D-26129, Oldenburg, Germany.
Nat Commun. 2018 Jun 20;9(1):2413. doi: 10.1038/s41467-018-04811-7.
Molecular chirality and the inherently connected differential absorption of circular polarized light (CD) combined with semiconducting properties offers great potential for chiral opto-electronics. Here we discuss the temperature-controlled assembly of enantiopure prolinol functionalized squaraines with opposite handedness into intrinsically circular dichroic, molecular J-aggregates in spincasted thin films. By Mueller matrix spectroscopy we accurately probe an extraordinary high excitonic circular dichroism, which is not amplified by mesoscopic ordering effects. At maximum, CD values of 1000 mdeg/nm are reached and, after accounting for reflection losses related to the thin film nature, we obtain a film thickness independent dissymmetry factor g = 0.75. The large oscillator strength of the corresponding absorption within the deep-red spectral range translates into a negative real part of the dielectric function in the spectral vicinity of the exciton resonance. Thereby, we provide a new small molecular benchmark material for the development of organic thin film based chiroptics.
分子手性和圆偏振光（CD）的固有差分吸收与半导体性质相结合，为手性光电带来了巨大的潜力。在这里，我们讨论了对映纯脯氨醇功能化方酸的温度控制组装，这些方酸具有相反的手性，在旋涂薄膜中形成固有圆二色性的分子 J 聚集体。通过 Mueller 矩阵光谱法，我们准确地探测到了极高的激子圆二色性，而这种圆二色性不会被介观有序效应放大。在最大值时，达到了 1000 mdeg/nm 的 CD 值，并且在考虑与薄膜性质相关的反射损耗后，我们得到了一个与薄膜厚度无关的不对称因子 g = 0.75。相应吸收在深红光光谱范围内的大振子强度转化为激子共振附近光谱中介电函数的负实部。因此，我们为基于有机薄膜的手性光学的发展提供了一种新的小分子基准材料。
