Effects of Bay Substituents on the Racemization Barriers of Perylene Bisimides:  Resolution of Atropo-Enantiomers

Abstract

The activation parameters for the interconversion of atropisomers (P- and M-enantiomer) of core-twisted perylene bisimides have been determined by dynamic NMR spectroscopy (DNMR) and time- and temperature-dependent CD spectroscopy. By comparing the activation parameters of a series of perylene bisimides containing halogen or aryloxy substituents in the bay area (1,6,7,12-positions), a clear structure-property relationship has been found that demonstrates that the kinetic and thermodynamic parameters for the inversion of enantiomers are dependent on the apparent overlap parameter Sigmar* of the bay substituents. This study reveals a high stability (DeltaG(368 K) = 118 kJ/mol) for the atropo-enantiomers of tetrabromo-substituted perylene bisimide in solution. Accordingly, the enantiomers of this derivative could be resolved by HPLC on a chiral column. These enantiomers do not racemize in solution at room temperature and, thus, represent the first examples of enantiomerically pure core-twisted perylene bisimides.

The Rylene Colorant Family—Tailored Nanoemitters for Photonics Research and Applications

“…This behavior is due to the electron-donating character of the phenoxy substituents and this effect can be enhanced further by increasing the donating character of the substituents by the introduction of meta or para-methoxy groups (2 b,c; Figure 2). [47] In the case of both PDI and TDI chromophores, the attachment of more-bulky substituents results in a slight twisting of the planar core of PDI chromophore 3 ( Figure 2) [48][49][50] as well as multiexponential fluorescence decays because of the conformational freedom of the substituents [49,51] (Table 1). Furthermore, the properties of higher excited states are influenced by the phenoxy groups.…”

Synthesis and Self‐Assembly of Bay‐Substituted Perylene Diimide Gemini‐Type Surfactants as Off‐On Fluorescent Probes for Lipid Bilayers

“…Partly substituted 1,6‐ and 1,7‐regioisomers, commonly as mixtures,44, 45, 46, 47, 48 have also been synthesised,49, 50 while 1,12‐bay‐substituted PDIs have been rarely reported. The latter are interesting because the distortion of the perylene ring system by the 1,12‐substitution will strongly alter the optical properties of the compound, comparable to their corresponding tetrasubstituted PDIs, while solubility and self‐assembly properties will be different 51, 52, 53. Unfortunately, 1,12‐bay‐substituted PDIs have to be accessed through halogenation/dehalogenation chemistry,54, 55, 56, 57 which is typically inefficient, cumbersome, and low yielding.…”

Energy Transfer Pathways in a Rylene‐Based Triad

“…[38][39][40][41][42][43][44][45] Among the various types of chromophores used, rylene dyes have been shown to be particularly useful for the investigation of multistep excitation energy transfer processes due to their high fluorescence quantum yield, chemical and photostability and the ability to fine-tune optical properties by proper substituents in the bay position. [46][47][48][49] They can be easily addressed in…”