有机π体系由于其特有的的光、电、磁学性质在光电元件中得到广泛的应用。目前绝大多数的有机π体系在基态下都具有闭壳的电子结构，但是我们最近发现一些具有特定结构的大π体系在基态下会以单线态双自由基的形式存在并呈现独特的物理性质和广阔的应用前景。然而，这类分子的合成非常具有挑战性，主要是因为它们具有很高的反应活性。本课题将设计、合成一系列新型稳定的、具有开壳结构的有机π自由基分子，研究它们的光学性质、电学性质和磁学性质，并进一步探索它们在非线性光学元件，两性场效应晶体管和太阳能电池等领域中的应用。我们的目标是弄清这类分子的结构-双自由基特征-物理性质之间最根本的联系，找到有效地稳定有机π自由基的合成方法，建立系统地表征这类分子基态下电子结构和物理性质的实验手段，并实现它们在有机光电磁材料和器件上的初步应用。

Organic π-systems have practical applications in optoelectronic devices due to their unique optical, electronic and magnetic properties. Currently, most organic π-systems have a closed-shell electronic structure in the ground state. We recently found that certain type of π-systems showed large singlet biradical character in the ground state and exhibited unusual physical properties and have potential applications in many areas. However, the synthesis of this type of molecules is challenging due to their high reactivity. In this proposal, we will design and synthesize a series of novel stable open-shell biradicals, study their unique optical, electronic and magnetic properties, and exploit their potential applications in non-linear optical devices, ambipolar field effect transistors and organic solar cells. Our aim is to find out the fundamental structure-biradical character-physical property relationship of this type of molecules, to develop efficient synthetic methods to stabilize the highly reactive radicals, to establish a systematic characterization method on the ground-state electronic structure and their physical properties, and to fulfill their preliminary applications in organic optoelectronic and magnetic materials and devices.