C3-Chiral truxenes showing high circularly polarized fluorescence and phosphorescence properties based on symmetry-forbidden transition

Abstract

Significant effort has been devoted to creating new molecules that show circularly polarized luminescence (CPL) and can be used in devices from both experimental and theoretical approaches. Here we show a new design strategy to achieve a large dissymmetric factor (g value) for CPL based on the symmetry-forbidden transition of π-conjugated molecules. This approach was successfully demonstrated by simple syn-5,10,15-trisubstituted truxenes exhibiting excellent g value for CPL on the order of 10–2. A Herzberg-Teller vibronic analysis and variable-temperature CPL measurements revealed that molecular vibrations dramatically lower the intensity of CPL. Furthermore, at low temperatures, syn-5,10,15-trimethyltruxene exhibits prolonged and strong phosphorescent CPL, which can be analyzed by calculating transition dipole moments using molecular orbitals in the triplet excited state. Leveraged on these findings, a conformationally rigid double-decker-type truxene with robust CPL properties at high temperatures was applied as an emitter in electroluminescence devices exhibiting CPL with a high g value.