# Synthesis of Conjugated Tris- and Tetrakis (Carbazolyl) Azulenes with Intense Emission in the Visible Range

## TL;DR

Scientists created new light-emitting compounds by attaching carbazolyl groups to azulene, resulting in intense blue light emission in the visible range.

## Contribution

The synthesis of tris- and tetrakis(carbazolyl)azulenes with intense visible light emission is newly demonstrated.

## Key findings

- Carbazolyl-substituted azulenes were synthesized in high yields using cross-coupling reactions.
- The compounds emit intense blue light in the visible range (444 and 490 nm) due to modified electronic structure.
- The donor properties of carbazolyl groups enable permitted HOMO-LUMO transitions for light emission.

## Abstract

New conjugated carbazolyl-substituted azulenes, such as 1,2,3-tris(carbazolyl)azulene and 1,2,3,6-tetrakis(carbazolyl)azulene, were synthesized via cross-coupling reactions in high yields. The resulting compounds exhibit a significant ability to absorb and emit light in the visible region, in the range of 400 to 600 nanometers. Studies have shown that azulene with carbazolyl substituents at positions 1, 2, 3, and 6 possesses unique photophysical properties, manifested as intense emission in the blue photoluminescence region (λPL at 444 and 490 nm), which is not observed in the original azulene. This feature arises due to the donor properties of carbazolyl substituents, which have a strong effect on the electronic structure of azulene, creating the conditions for a permitted HOMO-LUMO electronic transition.