Silole is a compound formed by replacing the bridgehead carbon atoms in cyclopentadiene with silicon atoms. In the silole structure, the σ bond of the outer ring of the silicon atom and the π bond of the cyclopentadiene form a σ-π conjugation, so that the lowest unoccupied orbital (LUMO) energy of the silole molecule is much lower than five-membered ring structures such as of pyrrole, furan, thiophene and pyrimidine. This property of silole makes it have strong electron affinity and high electron mobility, which plays an important role in the field of optoelectronic materials. For the functionalization of silole, the main purpose is to tune the electronic structure and luminescence properties of silole. The electronic structure of silole is largely affected by the substituents on the silole ring, especially the structural modification at positions 2 and 5 has the greatest impact on the LUMO energy level. In addition, the silicon atom of the silole unit adopts sp3 hybridization, and the introduction of two flexible chain substituents on the silicon atom can improve the solubility of the compound. In siloles small molecule semiconductor materials, in addition to directly modifying the simplest silole ring, structures such as silicon-bridged π-conjugated fused rings, bisilole thiophene, and spiro silole can also be formed. The unique electronic structures of silole derivatives makes them have excellent performance and unique photophysical properties, and are widely used in the fields of solar cells and organic optoelectronic materials.
Figure 1. Simple chemical structures of silole