A Novel Carbazolophane: A Comparison of the Performance of Two Planar Chiral CP‐TADF Emitters
Jasmin Seibert, Yan Xu, Hassan Hafeez, Joachim Podlech, Ludovic Favereau, Eduard Spuling, Charlotte Waldhelm, Martin Nieger, Olaf Fuhr, Zahid Hassan, Jeanne Crassous, Ifor D. W. Samuel, Eli Zysman‐Colman, Stefan Bräse
Abstract
Abstract The prototypical example of a (cyclo)phane, [2.2]paracyclophane (PCP), has proven to be a versatile stereogenic moiety within the design of circularly polarized thermally activated delayed fluorescence (CP‐TADF) emitters; however, the exploration of other cyclophanes within CP‐TADF emitter design has been largely neglected. Here, a comparative study of the photophysical and optoelectronic properties of two cyclophane emitters, (1,7) t BuCzpPhTrz and its isomer (1,4) t BuCzpPhTrz , is presented. The carbazolophane‐triazine compound (1,7) t BuCzpPhTrz , obtained via an unprecedented intramolecular rearrangement, is the first example of a planar chiral TADF emitter deviating from the PCP scaffold. Significant geometrical change of the enclosed carbazole in (1,7) t BuCzp results in an attenuation of the donor strength, while the merits of rigidity and steric bulk remain. In particular, the full width at half maximum (FWHM) of the photoluminescence spectrum in toluene of (1,7) t BuCzpPhTrz is reduced by 34% and blue‐shifted by 20 nm compared to that of (1,4) t BuCzpPhTrz . In doped films, the compounds reach high photoluminescence quantum yields ( Φ PL ) of 91 and 81%, respectively. The chiroptical properties reveal dissymmetry factors | g PL | of up to 5 × 10 −4 . These results demonstrate the impact of the cyclophane for the development of CP‐TADF materials and add to the currently limited scope of available planar chiral donors.