A Strategy for Site-Selective Functionalization of Cyan Groups: Turning Conventional Tadf Molecules into Chiral Tadf Emitters

Abstract

In this work, we use two strategies to construct chiral thermally activated delayed fluorescence (TADF) molecules. The D-A-D type molecules, BPsC-PXZ and BPmCbt-PXZ are obtained by changing the cyano (CN) position and chiral perturbation strategy, respectively. The singlet-triplet energy gap (ΔES1T1, ΔES1T2, ΔES1T3) of BPsC-PXZ is 0.08, 0.05 and 0.34 eV, severally. This provides multiple efficient channels for the exciton transition from the triplet to the singlet excited state. The small ΔEST and large spin-orbital coupling (SOC) values (=0.183 cm-1) enhance the intersystem crossing (ISC) and reverse intersystem crossing (RISC) processes for BPsC-PXZ. Overall, the switching of chiral TADF molecules can be achieved by changing the position of CN, which provides a feasible strategy for the development of chiral TADF materials.

Keywords: site-selective functionalization, singlet-triplet energy gap, Reverse intersystem crossing, chiral thermally activated fluorescence