Exploiting racemism enhanced organic room-temperature phosphorescence to demonstrate Wallach's rule in the lighting chiral chromophores

• Published in: Nature communications Vol. 11; no. 1; p. 2145
• Main Authors: Wu, Xiugang, Huang, Chun-Ying, Chen, Deng-Gao, Liu, Denghui, Wu, Chichi, Chou, Keh-Jiunh, Zhang, Bin, Wang, Yafei, Liu, Yu, Li, Elise Y, Zhu, Weiguo, Chou, Pi-Tai
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 01.05.2020; Nature Publishing Group UK; Nature Portfolio
• Subjects: Chromophores; Correlation analysis; Electroluminescence; Exploitation; Fluorescence; Light emission; Luminous intensity; Molecular structure; Organic light emitting diodes; Packing; Phosphorescence; Photoluminescence; Photons; Room temperature; White light
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-020-15976-5

The correlation between molecular packing structure and its room-temperature phosphorescence (RTP), hence rational promotion of the intensity, remains unclear. We herein present racemism enhanced RTP chiral chromophores by 2,2-bis-(diphenylphosphino)-1,1-napthalene (rac-BINAP) in comparison to its chiral counterparts. The result shows that rac-BINAP in crystal with denser density, consistent with a long standing Wallach's rule, exhibits deeper red RTP at 680 nm than that of the chiral counterparts. The cross packing between alternative R- and S- forms in rac-BINAP crystal significantly retards the bimolecular quenching pathway, triplet-triplet annihilation (TTA), and hence suppresses the non-radiative pathway, boosting the RTP intensity. The result extends the Wallach's rule to the fundamental difference in chiral-photophysics. In electroluminescence, rac-BINAP exhibits more balanced fluorescence versus phosphorescence intensity by comparison with that of photoluminescence, rendering a white-light emission. The result paves an avenue en route for white-light organic light emitting diodes via full exploitation of intrinsic fluorescence and phosphorescence.