Deracemization of Carbohelicenes by a Chiral Perylene Bisimide Cyclophane Template Catalyst

Abstract

Deracemization describes the conversion of a racemic mixture of a chiral molecule into an enantioenriched mixture or an enantiopure compound without structural modifications. Herein, we report an inherently chiral perylene bisimide (PBI) cyclophane whose chiral pocket is capable of transforming a racemic mixture of [5]-helicene into an enantioenriched mixture with an enantiomeric excess of 66 %. UV/Vis and fluorescence titration studies reveal this cyclophane host composed of two helically twisted PBI dyes has high binding affinities for the respective homochiral carbohelicene guests, with outstanding binding constants of up to 3.9 10 10 m À1 for [4]-helicene. 2D NMR studies and single-crystal X-ray analysis demonstrate that the observed strong and enantioselective binding of homochiral carbohelicenes and the successful template-catalyzed deracemization of [5]-helicene can be explained by the enzyme-like perfect shape complementarity of the macrocyclic supramolecular host.

The Pink Box: Exclusive Homochiral Aromatic Stacking in a Bis-perylene Diimide Macrocycle

“…Therefore, our aim was to exploit strong homochiral π–π stacking in macrocycle 1 to stabilize PDI enantiomers for functional chiroptical materials. Although bay and imide connectivity have been used simultaneously to prevent stereoisomer interconversion in a bis-PDI macrocycle, 43 we report an alternative strategy that uses only bay connectivity, making the imide positions available for future potential modifications.…”

The significance of nanoparticle shape in chirality transfer to a surrounding nematic liquid crystal reporter medium

“…Such intrinsically chiral cores have been reported for a number of anisometric nanomaterials including, for example, in a recent report by Ben-Moshe and colleagues for bipyramidal tellurium 28 or Markovich et al for rod-like Eu 3+ -doped terbium phosphate nanocrystals. 29 Given the recently increasing number of articles citing shape compatibility arguments, 30 recognized for simple molecular LC systems by Feringa and co-workers years ago, 31 we foresee that the utility of the mathematical and computational concepts described here may soon be significantly advanced by machine learning and artificial intelligence (AI) strategies, and as such support familiar 'you cannot put a square peg in a round hole' metaphors for molecular and nanoscale chirality transfer systems. Ultimately, a further expansion of these concepts to lyotropic LC systems 32,33 that are biologically significantly more relevant as well as to applications seems all but inevitable.…”

Perylene Bisimide Cyclophanes as Biaryl Enantiomerization Catalysts─Explorations into π–π Catalysis and Host–Guest Chirality Transfer

“…In 2015, Spenst and Würthner introduced a new class of conformationally rigid and chemically versatile cyclophanes consisting of para -xylene bridged perylene bisimide (PBI) moieties (Figure A) . The presence of the large perylene planes, the rigidity of the cyclophane cavity, and the ideal ∼7 Å cavity height created by the linking para -xylene groups were found to make these structures ideal receptors for large aromatic compounds. − …”