Pure Boric Acid Does Not Show Room‐Temperature Phosphorescence (RTP). (19th February 2022)

• Record Type: Journal Article
• Authors: Wu, Zhu; Roldao, Juan Carlos; Rauch, Florian; Friedrich, Alexandra; Ferger, Matthias; Würthner, Frank; Gierschner, Johannes; Marder, Todd B.
• Is Part Of: Angewandte Chemie. Volume 134:Number 15(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-02-19
• Subjects: Boric Acid -- Impurity -- Phosphorescence -- TD-DFT -- Triplet; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.202200599
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: Boric acid (BA) has been used as a transparent glass matrix for optical materials for over 100 years. However, recently, apparent room‐temperature phosphorescence (RTP) from BA (crystalline and powder states) was reported (Zheng et al., Angew. Chem. Int. Ed . 2021, 60, 9500) when irradiated at 280 nm under ambient conditions. We suspected that RTP from their BA sample was induced by an unidentified impurity. Our experimental results show that pure BA synthesized from B(OMe)3 does not luminesce in the solid state when irradiated at 250–400 nm, while commercial BA indeed (faintly) luminesces. Our theoretical calculations show that neither individual BA molecules nor aggregates would absorb light at >175 nm, and we observe no absorption of solid pure BA experimentally at >200 nm. Therefore, it is not possible for pure BA to be excited at >250 nm even in the solid state. Thus, pure BA does not display RTP, whereas trace impurities can induce RTP. Abstract : For over 100 years, boric acid (BA) has been known to serve as an excellent glass matrix for luminescent chromophores. However, in contrast to a recent report, pure BA does NOT display RTP when excited at 280 nm, and it is demonstrated experimentally that it does not absorb at λ >200 nm. Theoretical studies further reveal that pure BA cannot absorb at λ >175 nm. Thus, an impurity must be responsible for the apparent RTP in the previous report.