Millisecond Time-scale Photoluminescence of B-N-doped Tetrathienonaphthalene with Borane/Amine Substituents

BN-doped polycyclic aromatic hydrocarbons (PAHs) have attracted numerous attentions because of their fascinating optical and electronic properties. In this work, a series of electron-donor (amine)- and -acceptor (borane)-functionalized BN-doped polycyclic aromatic hydrocarbons were prepared to study the substituents' effect on the photophysical properties. As a result, the compound with both donor and acceptor, BN, exhibits both local emission (LE) and charge-transfer emission (CT) in polar solvents. Especially, the CT emission with a longer wavelength revealed a lifetime as long as millisecond time scale at room temperature, indicating typical phosphorescence characteristics. Low-temperature photoluminescent (PL) spectroscopy and a theoretical study were conducted to help to interpret this phenomenon, and it turned out to be the lowering of the S-1 energy level of BN which makes the intersystem crossing favorable. Furthermore, fluoride anion titration experiments exhibit the application potential of the dual-emission phenomenon of BN for ratiometric sensory materials.

Automated summary

This study prepared a series of electron-donor and -acceptor-functionalized BN-doped polycyclic aromatic hydrocarbons and found that compounds with both donor and acceptor exhibit both local emission and charge-transfer emission in polar solvents, with the charge-transfer emission showing phosphorescence characteristics and a long lifetime. The lowering of the S-1 energy level of BN makes intersystem crossing favorable, and the dual-emission phenomenon of BN shows potential for ratiometric sensory materials.