Antiaromatic characteristic analysis of 1,4-diazapentalene derivatives: a theoretical study

1,4-Diazapentalene heteroacenes are potential n-type semiconductors that could be used as a new type of material for organic field-effect transistors (OFETs), but their synthesis is still challenging due to their antiaromaticity. The study on their structure-stability relationship should provide useful guidance to the design of stable diazapentalenes. We examined the stability of several types of heteroacenes bearing the 1,4-diazapentalene core using NICS(1)zz calculations. The influence of the fusion pattern, the introduction of substituents, and the incorporation of other heterocycles on the antiaromaticity of the central 1,4-diazapentalene core was systematically studied. It was found that the linear fusion of aromatic rings to the antiaromatic core increases the stability of the heteroacene. The fusion of electron-poor heterocyclic rings also enhances the stability effectively, whereas the fusion of electron-rich heterocyclic rings destabilizes the system. In addition, the combination of the linear fusion pattern or introduction of electron-poor heterocyclic rings to the antiaromatic core reduces the reorganization energy for electron transport, suggesting a way to achieve better n-type semiconductors.