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

Xiugang Wu; Chun-Ying Huang; Deng-Gao Chen; Denghui Liu; Chichi Wu; Keh-Jiunh Chou; Bin Zhang; Yafei Wang; Yu Liu; Elise Y Li; Weiguo Zhu; Pi-Tai Chou

doi:10.1038/s41467-020-15976-5

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

Nat Commun. 2020 May 1;11(1):2145. doi: 10.1038/s41467-020-15976-5.

Authors

Xiugang Wu^#¹, Chun-Ying Huang^#², Deng-Gao Chen^#², Denghui Liu¹, Chichi Wu³, Keh-Jiunh Chou², Bin Zhang¹, Yafei Wang¹, Yu Liu¹, Elise Y Li³, Weiguo Zhu⁴, Pi-Tai Chou⁵

Affiliations

¹ School of Materials Science and Engineering, Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Jiangsu Engineering Laboratory of Light-Electricity-Heat Energy-Converting Materials and Applications, Jiangsu Key Laboratories of Environment-Friendly Polymers, National Experimental Demonstration Center for Materials Science and Engineering, Changzhou University, Changzhou, China.
² Department of Chemistry, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei, 10617, Taiwan, ROC.
³ Department of Chemistry, National Normal Taiwan University, No. 162, Sec. 1, Heping E. Rd., Taipei, 10610, Taiwan, ROC.
⁴ School of Materials Science and Engineering, Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Jiangsu Engineering Laboratory of Light-Electricity-Heat Energy-Converting Materials and Applications, Jiangsu Key Laboratories of Environment-Friendly Polymers, National Experimental Demonstration Center for Materials Science and Engineering, Changzhou University, Changzhou, China. zhuwg18@126.com.
⁵ Department of Chemistry, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei, 10617, Taiwan, ROC. chop@ntu.edu.tw.

^# Contributed equally.

Abstract

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.

Publication types

Research Support, Non-U.S. Gov't