Ultralong room-temperature phosphorescence from boric acid

For a long time, phosphors with long-lived emission are dominated by rare earth/transition metal ion-doped sulfides and oxides. Recently, organic materials capable of emitting long-lived room-temperature phosphorescence (RTP) are reported, carbon skeletons are almost the exclusive structural feature of the conjugated luminophores. Herein, we reported that boric acid, a non-metal and C-free material, could emit RTP with lifetime up to 0.3 s. Detailed investigations indicated the weak conjugation between the n electrons of the O atoms in the B-O confined space was the possible origin of RTP. Similar RTP was also found in electron-rich N/F systems, namely, BN and BF${}_3$ (BF${}_4^{-}$). Importantly, the vacant p${}_z^0$ orbital of B was found to contribute to the relevant unoccupied molecular orbitals involved in excitation, which is different from previous reports on phosphorescence from arylboronic acids. The results confirm the unique role of B as a versatile structure motif for construction of new RTP materials. (© 2021 Wiley-VCH GmbH)