Triarylborane‐Based Helical Donor–Acceptor Compounds: Synthesis, Photophysical, and Electronic Properties. Issue 46 (15th July 2019)

• Record Type: Journal Article
• Authors: Jia, Xiangqing; Nitsch, Jörn; Ji, Lei; Wu, Zhu; Friedrich, Alexandra; Kerner, Florian; Moos, Michael; Lambert, Christoph; Marder, Todd B.
• Is Part Of: Chemistry. Volume 25:Issue 46(2019)
• Page Start: 10845
• Page End: 10857
• Publication Date: 2019-07-15
• Subjects: boron -- charge transfer -- fluorescence -- helicenes -- luminescent; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201902258
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: 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)2 1 ) and 13‐(dimesitylboryl)‐ N, N ‐di‐ p ‐tolyldibenzo[ c, g ]phenanthren‐8‐amine (3‐B(Mes)2 ‐[5]helix‐12‐N( p ‐Tol)2 2 ) 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 ( Φ f =0.48 and 0.61 for1 and2, respectively), which are higher than unsubstituted ones ( Φ f =0.18 for [4]helicene; Φ f <0.05 for [ n ]helicenes ( n ≥5)). In the solid state, the Φ f values are higher ( Φ f =1.00 and 0.55 for1 and2, respectively) than those in solution, most likely due to the restrictions of molecular motions. The S1 ←S0 transitions of1 and2 are predominately HOMO→LUMO transitions. Upon excitation with UV light, the interplanar angle between the two terminal aryl rings of the [5]helix core of2 decreases (S1 state compared with S0 state), which is similar to placing a spring under an external force. Abstract : Triarylborane‐based helical D–π–A compounds have been prepared and their photophysical properties have been studied. These compounds have pronounced strong intramolecular charge‐transfer (ICT) transitions, and high quantum yields both in solution and especially in the solid state. Upon excitation by UV light, the helicene core contracts, similar to a spring under an external force.