Bialas David, Zitzler-Kunkel André, Kirchner Eva, Schmidt David, Würthner Frank
Universität Würzburg, Institut für Organische Chemie and Center for Nanosystems Chemistry, Am Hubland, 97074 Würzburg, Germany.
Nat Commun. 2016 Sep 29;7:12949. doi: 10.1038/ncomms12949.
Exciton coupling is of fundamental importance and determines functional properties of organic dyes in (opto-)electronic and photovoltaic devices. Here we show that strong exciton coupling is not limited to the situation of equal chromophores as often assumed. Quadruple dye stacks were obtained from two bis(merocyanine) dyes with same or different chromophores, respectively, which dimerize in less-polar solvents resulting in the respective homo- and heteroaggregates. The structures of the quadruple dye stacks were assigned by NMR techniques and unambiguously confirmed by single-crystal X-ray analysis. The heteroaggregate stack formed from the bis(merocyanine) bearing two different chromophores exhibits remarkably different ultraviolet/vis absorption bands compared with those of the homoaggregate of the bis(merocyanine) comprising two identical chromophores. Quantum chemical analysis based on an extension of Kasha's exciton theory appropriately describes the absorption properties of both types of stacks revealing strong exciton coupling also between different chromophores within the heteroaggregate.
激子耦合至关重要，它决定了有机染料在（光）电子器件和光伏器件中的功能特性。在此我们表明，强激子耦合并不局限于通常所认为的等发色团情况。分别由具有相同或不同发色团的两种双（部花青）染料获得了四重染料堆叠，它们在极性较小的溶剂中会二聚形成相应的同聚集体和异聚集体。四重染料堆叠的结构通过核磁共振技术确定，并通过单晶X射线分析得到明确证实。由带有两种不同发色团的双（部花青）形成的异聚集体堆叠与由包含两个相同发色团的双（部花青）形成的同聚集体相比，呈现出明显不同的紫外/可见吸收带。基于对卡沙激子理论的扩展进行的量子化学分析，恰当地描述了两种堆叠类型的吸收特性，揭示了异聚集体中不同发色团之间也存在强激子耦合。
