Chiral Perylene Bisimide Dyes by Interlocked Arene Substituents in the Bay Area

Abstract

A series of perylene bisimide (PBI) dyes bearing various aryl substituents in 1,6,7,12 bay positions has been synthesized by Suzuki cross‐coupling reaction. These molecules exhibit an exceptionally large and conformationally fixed twist angle of the PBI π‐core due to the high steric congestion imparted by the aryl substituents in bay positions. Single crystal X‐ray analyses of phenyl‐, naphthyl‐ and pyrenyl‐functionalized PBIs reveal interlocked π‐π‐stacking motifs, leading to conformational chirality and the possibility for the isolation of enantiopure atropoisomers by semipreparative HPLC. The interlocked arrangement endows these molecules with substantial racemization barriers of about 120 kJ mol−1 for the tetraphenyl‐ and tetra‐2‐naphthyl‐substituted derivatives, which is among the highest racemization barriers for axially chiral PBIs. Variable temperature NMR studies reveal the presence of a multitude of up to fourteen conformational isomers in solution that are interconverted via smaller activation barriers of about 65 kJ mol−1. The redox and optical properties of these core‐twisted PBIs have been characterized by cyclic voltammetry, UV/Vis/NIR and fluorescence spectroscopy and their respective atropo‐enantiomers were further characterized by circular dichroism (CD) and circular polarized luminescence (CPL) spectroscopy.

Enantioselective Recognition of Helicenes by a Tailored Chiral Benzo[ghi]perylene Trisimide π‐Scaffold

“…Indeed, temperature‐dependent studies on the racemization rate of BPTI 7 in high‐boiling diphenylether (Figure S11) confirm this expectation with an activation barrier of Δ G ≠ 483 K =160 kJ mol −1 (Table S2) that corresponds quite perfectly to the one observed for BINOL (Δ G ≠ 483 K =165 kJ mol − ) [11] . This value is far above those previously realized for bay‐functionalized PBIs (<120 kJ mol −1 ) [4, 12] . and even [6]helicene (estimated to Δ G ≠ 483 K =155 kJ mol −1 ) , [13] thereby demonstrating that BINOL‐functionalized BPTIs are robust chiral scaffolds even at elevated temperatures up to around 150 °C as desired for applications including further chemical derivatization.…”

“…[11] This value is far above those previously realized for bayfunctionalized PBIs (< 120 kJ mol À 1 ). [4,12] and even [6]helicene (estimated to ΔG � 483 K = 155 kJ mol À 1 ) , [13] thereby demonstrating that BINOL-functionalized BPTIs are robust chiral scaffolds even at elevated temperatures up to around 150 °C as desired for applications including further chemical derivatization.…”

Substituent-dependent absorption and fluorescence properties of perylene bisimide radical anions and dianions

“…Together with the structured fluorescence spectrum such high quantum yield corroborates the rigidification effect impaired by the four phenyl units that are interlocked based on the crystallographic evidence from the related chromophores. 57 The neutral PBI-ClCN exhibits only very weak fluorescence upon excitation at 490 nm, with a l em at 575 nm and a F f of merely 0.1%. Because this is much lower than the reported quantum yield of 11% of the neutral congener with electron-withdrawing fluoroalkyl chains in the imide position we attribute the fluorescence quenching to a photoinduced electron transfer from the Dipp substituent into the highly electron-deficient core.…”

Chirality of Perylene Diimides: Design Strategies and Applications

“…Another method to obtain considerable racemization barriers is through the direct attachment of bulky groups at the bay positions of PDIs. [16] Recently, Würthner and coworkers reported a series of aryl-substituted PDIs (5, Figure 2d) and successfully isolated enantiopure 5 a and 5 c [17] The overlapping of the arene substituents endows 5 a and 5 c with substantial racemization barriers of about 120 kJ mol À 1 in solution, which is among the highest racemization barriers for axially chiral PDIs. This barrier results in the enantiomers exhibiting chiral features and CPL properties at room temperature.…”