Copper-free click chemistry between azides and internal alkynes for triphenylene discotic liquid crystal trimer formation

Abstract

Click chemistry continues to attract much attention and is widely used in a variety of synthetic areas. However, it is a challenge to do this type of reaction in the absence of a copper catalyst. In this report, we overcome this problem and synthesise two non-C ₃ symmetric triphenylene discotic liquid crystal trimers by a copper-free click reaction involving a linear internal alkyne and an azide. Both products are liquid crystals at room temperature; one trimer exhibits an ordered hexagonal columnar mesophase (Col_ho) and a plastic hexagonal columnar mesophase (Col_hp) on cooling, and just a plastic hexagonal columnar on heating, whilst the other displays an ordered rectangular columnar mesophase (Col_ro).

Keywords:

• copper-free click chemistry
• triphenylene
• trimer
• oligomer
• room temperature liquid crystal

Acknowledgements

We are grateful to the National Natural Science Foundation of China (Nos.51073112, 50973076, and 51273133) and The Youth Foundation of Sichuan Educational Committee (10ZB007) for support of this project.