Efficient helical columnar emitters of chiral homoleptic Pt(<scp>ii</scp>) metallomesogens for circularly polarized electroluminescence

Abstract

Chiral organometallic Pt(ii) complexes have been demonstrated to be excellent circularly polarized luminescence (CPL) materials due to their rich phosphorescence and strong self-assembly characteristics. However, it remains a formidable task to simultaneously achieve high luminance (<i>L</i>) and electroluminescence dissymmetry factor (<i>g</i> _EL) values for circularly polarized electroluminescence (CP-EL) devices of Pt(ii) complex-based emitters. In this study, we carry out a straightforward and efficient protocol to construct highly CPL-active helical columnar () emitters by using chiral homoleptic triazolatoplatinum(ii) metallomesogens (<i>R</i>/<i>S</i>-HPt). The peripheral flexible groups can not only improve solubility but also favor the induction of chirality and liquid crystal behavior. The resultant complexes <i>R</i>/<i>S</i>-HPt can self-assemble into the mesophase over a broad temperature range (6-358 °C) and exhibit excellent phosphorescence (<i>Φ</i>: up to 86%), resulting in intense CPL signals after thermal annealing (<i>λ</i> _em = 615 nm and |<i>g</i> _em| = 0.051). Using emitting layers (EML) based on <i>R</i>/<i>S</i>-HPt in solution-processed CP-EL devices, <i>L</i> _max and |<i>g</i> _EL| of CP-EL can reach up to 11 379 cd m^-2 and 0.014, respectively. With comprehensive consideration of <i>L</i> _max and <i>g</i> _EL, this investigation shows the excellent performances among Pt(ii) complex-based CP-EL devices.