Red Room-Temperature Phosphorescence from a Sustainable Source

Phosphorescent materials show luminescence, i.e., they emit light, for a period of time after the excitation source is removed. Organic materials that show room-temperature phosphorescence can be useful, e.g., in imaging, organic light-emitting diodes (OLEDs), or anti-counterfeiting applications. Most existing materials of this kind are prepared from fossil resources, and the development of room-temperature phosphorescence materials from renewable feedstocks is an interesting research target. Existing examples of biomass-derived materials of this type often show a blue or green emission, while examples with red emission are rare.

Qingjiang Pan, Heilongjiang University, Harbin, China, Tony D. James, University of Bath, UK, Henan Normal University, Xinxiang, China, Zhijun Chen, Northeast Forestry University, Harbin, China, and colleagues have developed a red room-temperature phosphorescence material from lignin, a renewable resource and a byproduct of the paper industry. The team introduced Upy (1-(6-isocyanatohexyl)-3-(6-methyl-4-oxo-1,4-dihydropyrimidin-2-yl) urea) units into the lignin via a reaction involving the isocyanate group of Upy and the OH groups of lignin.

The resulting Upy-modified lignin features strong intermolecular hydrogen bonding interactions (pictured), which promote closer interactions between the aromatic subunits of the lignin. This results in a red room-temperature phosphorescence emission, centered at 625 nm with a lifetime of 24.2 ms. The hydrogen bonding interactions can be influenced by different matrices in which the modified lignin is embedded, which then also changes the phosphorescence properties. This can be used, e.g., to realize phosphorescence with different lifetimes and materials with time-dependent color changes.

Red room temperature phosphorescence from lignin,
Hongda Guo, Huanjie Cheng, Ruixia Liu, Xiaoxia Chen, Luyao Wang, Chenhui Yang, Shujun Li, Shouxin Liu, Jian Li, Qingjiang Pan, Tony D James, Zhijun Chen,
Angew. Chem. Int. Ed. 2024.
https://doi.org/10.1002/anie.202421112

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