Impact of Truncation on Optoelectronic Properties of Azaborole Helicenes

• Published in: Chemistry : a European journal Vol. 29; no. 70; pp. e202302808 - n/a
• Main Authors: Full, Julian, Wildervanck, Martijn J., Dillmann, Claudia, Panchal, Santosh P., Volland, Daniel, Full, Felix, Meerholz, Klaus, Nowak‐Król, Agnieszka
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 14-12-2023
• Subjects: azaboroles; Chemistry; Circular polarization; circularly polarized organic light-emitting diodes (CP-OLEDs); fluorescence; helicenes; Isomers; Optoelectronics; Organic light emitting diodes; Phosphorescence; Photoluminescence; Photons; Polymers; phosphorescence; azaboroles; helicenes; circularly polarized organic light-emitting diodes (CP-OLEDs); fluorescence
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202302808

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 gEL of up to 0.54.
Removal of C=C bonds from azabora[7]helicenes strongly impacts their optoelectronic properties. The truncated compounds show photoluminescence quantum yields of up to 0.53 in the solid state and phosphorescence with lifetimes of up to ~0.5 s. A methyl complex of azabora[7]helicene was used as a chiral inducer embedded in an emissive polymer (F8BT) to produce CP‐OLEDs with gEL of 0.54.