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Enhanced Optical Properties of Azaborole Helicenes by Lateral and Helical Extension
Author(s) -
Full Felix,
Wölflick Quentin,
Radacki Krzysztof,
Braunschweig Holger,
NowakKról Agnieszka
Publication year - 2022
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202202280
Subject(s) - luminescence , helicene , conjugated system , phenanthrene , chemistry , crystallography , stereochemistry , chrysene , elongation , materials science , polymer , molecule , organic chemistry , optoelectronics , ultimate tensile strength , metallurgy
The synthesis and characterization of laterally extended azabora[5]‐, ‐[6]‐ and ‐[7]helicenes, assembled from N ‐heteroaromatic and dibenzo[ g , p ]chrysene building blocks is described. Formally, the π‐conjugated systems of the pristine azaborole helicenes were enlarged with a phenanthrene unit leading to compounds with large Stokes shifts, significantly enhanced luminescence quantum yields (Φ) and dissymmetry factors ( g lum ). The beneficial effect on optical properties was also observed for helical elongation. The combined contributions of lateral and helical extensions resulted in a compound showing green emission with Φ of 0.31 and | g lum | of 2.2×10 −3 , highest within the series of π‐extended azaborahelicenes and superior to emission intensity and chiroptical response of its non‐extended congener. This study shows that helical and lateral extensions of π‐conjugated systems are viable strategies to improve features of azaborole helicenes. In addition, single crystal X‐ray analysis of configurationally stable [6]‐ and ‐[7]helicenes was used to provide insight into their packing arrangements.