Three isomers of quinodimethanes (QDMs) adopt different electronic configurations and geometries, generating their own characteristic physical properties. Incorporation of QDMs into non-benzenoid aromatic or antiaromatic frameworks not only planarizes the whole π system optimizing conjugation, but also changes the electronic properties inherent to QDMs, sometimes drastically, due to the topology of the π system, through interaction with the remaining part of the molecules. In non-benzenoid systems, molecular orbital levels and orbital distribution are uneven compared to benzenoid systems, thereby polarizing the ground state and leading to unique behavior in excited states. In antiaromatic systems, open-shell, diradical character, which is inherent to QDMs, may be enhanced due to small HOMO–LUMO energy gap. In this chapter, effects of incorporating QDMs into non-benzenoid aromatic or antiaromatic frameworks are discussed focusing on the open-shell, diradical character with respect to their molecular structures, antiaromaticity, and physical properties related to the open-shell character and molecular orbital levels and materials applications, as well as covering historical works to the current state-of-the-art achievements.

醌二甲烷（QDM）的三种异构体采用不同的电子构型和几何形状，产生了自己的特征物理性质。将QDM掺入非苯型芳香族或抗芳香族骨架中，不仅使整个π系统平坦化，优化了共轭，而且还由于π系统的拓扑结构，与其他部分的相互作用，极大地改变了QDM固有的电子性能。分子。在非本烯系中，与本烯系相比，分子轨道的水平和轨道分布是不均匀的，从而使基态极化并导致激发态下的独特行为。在抗芳香族系统中，由于较小的HOMO-LUMO能隙，可能会增强QDM固有的开壳双自由基特性。在这一章当中，