Description

Indocarbazole is a class of heterocyclic compounds whose structure includes a planar ring system composed of indole and carbazole elements. It was first discovered in Streptomycetes and subsequently isolated from many representatives of plants and animals. Indocarbazole has a variety of properties, including antitumor activity, antibacterial and antifungal activity, and antiviral activity. Depending on the structure of the flat aromatic ring system, indolocarbazole include five subclasses of compounds that belong to the five isomers of polycyclic systems (as shown in the figure below): indolo[2,3-a]carbazole (1), indolo[2,3-b]carbazole (2), indolo[2,3-c]carbazole (3), indolo[3,2-a]carbazole (4), and indolo[3,2-b]carbazole (5). Among them, the subclass of derivatives of 11,12-Dihydroindolo[2,3-a]carbazole is the most common and its biological significance is very important[1].

Property

11,12-Dihydroindolo[2,3-a]carbazole is also known as indolo[2,3-a]carbazole. Its molecular formula is C₁₈H₁₂N₂, and it is a white to light yellow powder. Its melting point is 371°C and needs to be sealed and stored in a dry environment. In the presence of acidic media, indole [2,3-a]carbazole is synthesized in a pot reaction by Fischer-indole synthesis using 2-amino-cyclohexanone hydrochloride and substituted aryl-hydrazines hydrochloride as raw materials. Indole [2,3-a]carbazole can also be synthesized from 1,2-cyclohexanedione and phenylhydrazine hydrochloride[2-3].

Application

Carbazole derivatives have the advantages of excellent solubility, coplanarity, substantial intramolecular charge transfer, stability, and simple structure modification. Among them, indole[2,3-a]carbazole has a larger mass planar conjugated structure, which is more conducive to electron transfer, and has strong structural tunability and excellent luminescence performance, so it is often used as a probe for detecting cations. Chen et al. prepared a highly selective and sensitive metal ion colorimetric sensor using the indole[2,3-a]carbazole group as the chromophore. The probe can specifically detect Cu²⁺ and Fe³⁺[4]. Indole[2,3-a]carbazole was used as raw material to prepare the small molecule 2-biphenyl-4,6-bis(12-phenylindolo[2,3-a]carbazole-11-yl)-1,3,5-triazine(PIC-TRZ). The molecule breaks the restriction of a large energy gap, with a ΔE1?3 of just 0.11 eV, while maintaining a high fluorescent radiative decay rate (kr～10⁷)[5].

References

[1] Zenkov R, et al. Indolo[2,3- a ]carbazoles: diversity, biological properties, application in antitumor therapy. Chemistry of Heterocyclic Compounds, 2020; 56: 644–658.

[2] Barry J, et al. On the [42]Cycloaddition Approach to Indolo[2,3-a]carbazoles. Tetrahedron, 1995; 51: 12797-12806.

[3] Klenkler R, et al. High electron mobility triazine for lower driving voltage and higher efficiency organic light emitting devices. Organic Electronics, 2008; 9: 285–290.

[4]Chen Z, et al. A simple indolo[2,3-a]carbazole based colorimetric chemosensor for simultaneous detection of Cu2+ and Fe3+ ions. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2020; 234: 118236.

[5] Endo A, et al. Efficient up-conversion of triplet excitons into a singlet state and its application for organic light emitting diodes. Applied Physics Letters, 2011; 98.