This chapter describes a series of heterocyclic quinodimethanes mainly containing O, N, S and Si atoms in their frameworks with either closed- or open-shell electronic structures in the ground state. Their syntheses, structural characterizations and chemical and physical properties are comprehensively reviewed. Some of them are used as materials for dyes/pigments and semiconductors for organic electronics. Some of them show an open-shell singlet diradical character with unusual properties. The purpose of this chapter is to provide fundamental understanding on the structure-property relationships of quinoidal π-conjugated compounds and give some insight into the rational design of such molecules with desirable properties.

本章介绍了一系列杂环喹二甲烷，它们的骨架中主要包含O，N，S和Si原子，基态为闭壳或开壳电子结构。对它们的合成，结构表征以及化学和物理性质进行了全面的综述。其中一些用作染料/颜料和有机电子产品的半导体材料。它们中的一些显示出具有不寻常性质的开壳单重双峰基特征。本章的目的是提供对quinoidalπ-共轭化合物的结构-性质关系的基本了解，并对具有所需特性的此类分子的合理设计提供一些见识。