Subtle structure tailoring of metal-free triazine luminogens for highly efficient ultralong organic phosphorescence

Ultralong organic phosphorescent materials have invoked considerable attention for their great potential in sensing, data encryption, information anti-counterfeiting and so forth. However, effective ways to achieve highly efficient ultralong organic phosphorescence (UOP) in metal-free organic materials remain a great challenge. Herein, we designed three isomers based on asymmetric triazines with various bromine substituted positions. Impressively, phosphorescence efficiency of p-BrAT in solid state can reach up to 9.7% with a long lifetime of 386 ms, which was one of the highest efficient UOP materials reported so far. Theoretical calculations further demonstrated that para-substitution exhibited the most effective radiative transition for triplet excitons. These results will provide an effective approach to achieving highly efficient UOP materials. (C) 2019 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.