Synthesis, Crystal Structure and Photophysical Properties of Pyrene–Helicene Hybrids. Issue 48 (21st October 2013)

• Record Type: Journal Article
• Authors: Bédard, Anne‐Catherine; Vlassova, Anna; Hernandez‐Perez, Augusto C.; Bessette, André; Hanan, Garry S.; Heuft, Matthew A.; Collins, Shawn K.
• Is Part Of: Chemistry. Volume 19:Issue 48(2013)
• Page Start: 16295
• Page End: 16302
• Publication Date: 2013-10-21
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201301431
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Synthesis of helically chiral aromatics resulting from fusion of pyrene and [4]‐ or [5]helicene has been accomplished using photoredox catalysis employing a Cu‐based sensitizer as the key step. Photocyclisation experiments for the synthesis of the target compounds were carried out in batch and using continuous flow strategies. The solid‐state structures, UV/Vis absorption spectra and fluorescence spectra of the pyrene–helicene hybrids were investigated and compared to that of the parent [5]helicene to discern the effects of merging a pyrene moiety within a helicene skeleton. The studies demonstrated that pyrene–helicene hybrids adopt co‐planar or stacked arrangements in the solid state, in contrast to the solid‐state structure of the parent [5]helicene. The UV/Vis and fluorescence spectra of the pyrene–helicene hybrids exhibited strong red‐shifts when compared to the parent [5]helicene. DFT calculations suggest that the strategy of extending the π surface in the <italic>y</italic> axis of the helicenes increased their HOMO levels while also decreasing their LUMO levels, resulting in significantly reduced band gaps.</p> </abstract>