Imidazoles are a class of five-membered aromatic heterocyclic compounds, which can form a variety of structures depending on the substitution position and number of N, the most common being 1,3-oxadiazole with two meta-position N atoms. Benzimidazole is a compound in which a benzene ring is combined with an imidazole ring, and is a type of heterocyclic structure containing two N atoms. On the one hand, the molecular system contains a good rigid planar structure and abundant π electrons. The π-π stacking of aromatic rings makes benzimidazole and its derivatives have good stability and fluorescence properties, and are widely used in light-emitting materials. On the other hand, because of the electron-deficient heterocyclic group (imidazole ring) contained in the molecular structure, the electron affinity is effectively improved, so that the benzimidazole derivatives can effectively transport electrons and are widely used as electron transport materials. Benzimidazole derivatives have been developed as blue light-emitting materials, electron transport materials, and host materials, and are widely used in the field of optoelectronics.
Figure 1. Chemical structure of benzimidazole
- Organic electroluminescent devices: In light-emitting devices, benzimidazole derivatives can be used as light-emitting materials and electron transport materials. The structure of benzimidazole endows it with good thermal stability and becomes a class of high-temperature-resistant organic semiconductor materials. As an electron transport material, it can improve the stability of light-emitting devices and make light emission more sustainable and efficient. At the same time, the broadband system of benzimidazole derivatives can effectively confine pairs of carriers and excitons in the light-emitting layer, which can further stabilize the device performance. As a light-emitting material, benzimidazole itself has strong blue fluorescence. By introducing other luminescent groups into the imidazole ring, the luminous efficiency and luminescent color of such materials can be enriched.
- Bipolar semiconductor materials: Benzimidazole is a good electron-transporting group, which can be combined with other hole-transporting groups to prepare ambipolar semiconductor materials with good performance and stable transport. Moreover, the good solubility of the benzimidazole derivatives makes the preparation simple and efficient. Such materials can be used in organic field effect transistors to improve the transport efficiency of carriers.
- Umesh Warde, Lydia Rhyman, Ponnadurai Ramasami, Nagaiyan Sekar. DFT Studies of the Photophysical Properties of Fluorescent and Semiconductor Polycyclic Benzimidazole Derivatives [J]. J. Fluoresc. 2015, 25, 685–694.