Impact of Truncation on Optoelectronic Properties of Azaborole Helicenes
Julian Full, Martijn Wildervanck, Claudia Dillmann, Santosh P. Panchal, Daniel Volland, Felix Full, Klaus Meerholz, Agnieszka Nowak‐Król
Abstract
Abstract Herein, we report configurationally stable singly‐truncated ( ST ) and structurally flexible doubly‐truncated ( DT ) helically chiral compounds derived from azabora[7]helicenes by a hypothetical removal of a single or two C=C double bonds. The singly‐truncated constitutional isomers were synthesized from either benzoisoquinoline (BIQ) or phenantherene building blocks and the corresponding biaryls in excellent yields to give azabora[5]helicenes with a pendant phenyl ring at a sterically hindered position. These systems highlight the electronic impact of the nitrogen donor substitution position. The compounds with a disrupted BIQ moiety ( STN ) possess remarkable photoluminescence quantum yields of up to 0.53 in the solid state and a blue emission in solution with dissymmetry factors of up to ca. 3×10 −3 . Upon cooling to 79 K all compounds exhibit phosphorescence with lifetimes of up to ca. 0.5 s. A methyl complex of azabora[7]helicene showing excellent configurational stability was used as a chiral inducer embedded in an emissive polymer (F8BT) to produce circularly polarized organic light emitting diodes with an electroluminescence dissymmetry factor g EL of up to 0.54.