A Near‐Infrared Absorbing and Emissive Quadruple Helicene Enabled by the Scholl Reaction of Perylene

Abstract

Herein, we report the synthesis, structural analysis, optical and chiroptical properties of a novel quadruple helicene, which has two [6] and two [7]helicene moieties fused in a contorted framework of 92 sp2 carbon atoms. It was synthesized by the Scholl reaction of a perylene‐containing substrate with the formation of eight carbon‐carbon bonds on the perylene unit in a single synthetic operation. Chemical oxidation of the quadruple helicene with tris(4‐bromophenyl)ammoniumyl hexachloroantimonate resulted in an air‐stable dication, which exhibits the same helicity in its four helicene moieties as unambiguously identified by single‐crystal X‐ray crystallography. The quadruple helicene exhibits unusual near‐infrared absorption and emission with absorption and emission maxima at 848 nm and 977 nm, respectively, and its isolated enantiomers exhibit electronic circular dichroism in the near‐infrared and visible‐light regions.

Robust Radical Cations of Hexabenzoperylene Exhibiting High Conductivity and Enabling an Organic Nonvolatile Optoelectronic Memory

“…This study demonstrates a new example for organic electronic materials based on contorted polycyclic aromatics, which offer interesting electronic and optical properties and self-assembly that are not available to flat π-molecules. This study, together with earlier reports on the cations of multiple helicenes, , leads to a hypothesis that multiple helicenes may be used as a general platform to develop stable π-conjugated radical cations. Further studies to test this hypothesis are in progress in our laboratory.…”

The Scholl Reaction as a Powerful Tool for Synthesis of Curved Polycyclic Aromatics

“…Very recently, Qiu and co-workers reported the Scholl reaction of tetra­(terphenyl)­perylene 201a with rearrangement as shown in Scheme a . Interestingly, Miao and co-workers reported the rearrangement-free Scholl reaction of 201b , which differs from 201a by having methoxy groups attached to the pendant phenyl groups, in the same month and in the same journal . Treatment of 201a with DDQ (12 equiv)/CF 3 SO 3 H gave helical nanographenes 202 and 203 as two regioisomers in a yield of 53% with a ratio of 5:2.…”

Multiple [n]helicenes with various aromatic cores

“…In contrast to double helicenes 29 and 30 , Miao et al 38 reported a quadruple helicene 31 with a perylene core, two [7] helicenes, and [6]helicene units (Figure 8a). Their synthetic strategy was almost the same as that of Qiu et al except for replacing the triphenyl group with a 4-methoxytriphenyl group.…”

“…(d) The UV-vis-NIR and fluorescence spectrum of 31. Adapted with permission 38. Copyright 2022, Wiley.…”