School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, USA.
J Am Chem Soc. 2010 Sep 8;132(35):12208-9. doi: 10.1021/ja104696e.
Interchain interactions between pi-systems have a strong effect on the electronic structure of conjugated organic materials. This influence has previously been explored by the spectroscopic and electrochemical characterization of molecules in which pairs of conjugated oligomers are held in a stacked fashion by attachment to a rigid scaffold. We have prepared a new polymer which uses a pseudo-geminal disubstituted [2.2]paracyclophane scaffold to hold 1,4-bis(phenylethynyl)-2,5-dialkoxybenzene (PE(3)) chromophores in a pi-stacked fashion over their entire length and in an extended multitier arrangement. Solutions of this new polymer display a Stokes shift of 171 nm, compared to just ca. 30 nm for previous models in which only the terminal phenyl rings of the PE(3) chromophore are held in a stacked arrangement. This suggests that interchain interactions of pi-systems over their entire length in a multitier assembly provides for relaxation of the excited state to a stable "phane" electronic state which is responsible for emission. This stabilization is not available in the stacked dimer or other regioisomers of the polymer which possess lesser degrees of overlap. Thus, the architecture of the soluble polymer mimics that of segments of conjugated polymers in semiconducting thin films and will provide a platform for the exploration of the nature of charge carriers and excitons in these important materials.
π-体系之间的链间相互作用对共轭有机材料的电子结构有很强的影响。这种影响以前是通过对分子的光谱和电化学特性进行研究来探索的，这些分子中的一对共轭低聚物通过附着在刚性支架上以堆叠的方式保持在一起。我们已经制备了一种新的聚合物，该聚合物使用伪孪生二取代[2.2]对环芳烷支架将 1,4-双（苯乙炔基）-2,5-二烷氧基苯（PE（3））发色团在其整个长度上以π-堆叠的方式和扩展的多层排列方式保持在一起。与以前的模型相比，该新型聚合物的溶液显示出 171nm 的斯托克斯位移，而在以前的模型中，仅 PE（3）发色团的末端苯环以堆叠方式排列。这表明，在多层组装中，整个π-体系之间的链间相互作用为激发态提供了松弛到稳定的“芳烷”电子态的机会，这是发射的原因。这种稳定在堆叠二聚体或聚合物的其他区域异构体中是不可用的，这些异构体的重叠程度较低。因此，可溶性聚合物的结构模拟了半导体薄膜中共轭聚合物的片段的结构，并且将为这些重要材料中的电荷载流子和激子的性质的研究提供一个平台。
