Departament de Química Orgànica, Universitat de Barcelona, c. Martí i Franquès 1, Barcelona, Catalonia, Spain.
Chirality. 2011 Sep;23(8):585-92. doi: 10.1002/chir.20975. Epub 2011 Jul 13.
Spontaneous symmetry breaking in J-aggregates of cyanine dyes has a long history in chemical literature. In 1976, Honda and Hada claimed that they had achieved chiral induction (CD) by stirring J-aggregates of pseudocyanine. However, this report is controversial, as the combinations of linear dichroism and birefringence can lead to artifactual circular dichroic signals that are unrelated to molecular chirality. A Mueller matrix spectroscopy study, with an approach for the application of a gradient of the shear rate (solution layer between a rotating and a fixed disk) that differs from the simple vortex stirring used in the original report, shows that true CD can be induced in the sample. The phenomenon is discussed, taking into account the flow dynamics that allows the alignment of the aggregate particles and the gradient of shear rates that determines their folding/torsion, which leads to a chiral excitonic transition.
聚集体中的自发对称破缺在氰染料的化学文献中由来已久。1976 年，本田和羽田声称，他们通过搅拌拟青霉素的 J-聚集体实现了手性诱导（CD）。然而，这一报道颇具争议，因为线性二色性和双折射的组合可能导致与分子手性无关的人为圆二色信号。穆勒矩阵光谱学研究采用了一种不同于原始报告中简单涡旋搅拌的方法，即在旋转盘和固定盘之间的溶液层施加剪切率梯度，表明可以在样品中诱导真正的 CD。考虑到允许聚集颗粒排列的流动动力学以及确定它们折叠/扭转的剪切率梯度，讨论了这一现象，这导致了手性激子跃迁。
