Triarylborane‐Based Helical Donor–Acceptor Compounds: Synthesis, Photophysical, and Electronic Properties.

Jia, Xiangqing; Nitsch, Jörn; Ji, Lei; Wu, Zhu; Friedrich, Alexandra; Kerner, Florian; Moos, Michael; Lambert, Christoph; Marder, Todd B.

The synthesis and characterization of 10‐(dimesitylboryl)‐N,N‐di‐p‐tolylbenzo[c]phenanthren‐4‐amine (3‐B(Mes)2‐[4]helix‐9‐N(p‐Tol)21) and 13‐(dimesitylboryl)‐N,N‐di‐p‐tolyldibenzo[c,g]phenanthren‐8‐amine (3‐B(Mes)2‐[5]helix‐12‐N(p‐Tol)22) are reported herein. Their electrochemical and photophysical properties have been studied experimentally and theoretically. The donor and acceptor‐substituted helicene derivatives exhibit moderate fluorescence quantum yields in THF (Φf=0.48 and 0.61 for 1 and 2, respectively), which are higher than unsubstituted ones (Φf=0.18 for [4]helicene; Φf<0.05 for [n]helicenes (n≥5)). In the solid state, the Φf values are higher (Φf=1.00 and 0.55 for 1 and 2, respectively) than those in solution, most likely due to the restrictions of molecular motions. The S1←S0 transitions of 1 and 2 are predominately HOMO→LUMO transitions. Upon excitation with UV light, the interplanar angle between the two terminal aryl rings of the [5]helix core of 2 decreases (S1 state compared with S0 state), which is similar to placing a spring under an external force.

FLUORESCENCE yield; INTRAMOLECULAR proton transfer reactions; QUANTUM dot synthesis

Chemistry - A European Journal, 2019, Vol 25, Issue 46, p10845

0947-6539

Academic Journal

10.1002/chem.201984663