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.

Preferential molecular recognition of heterochiral guests within a cyclophane receptor

“…14c). The vibronic fine structure of the S 0 → S 1 absorption band at ~600 nm is less pronounced than for other bay substituted perylene bisimide cyclophanes 22,35,47 and the absorbance of the S 0 → S 2 band is rather strong which could be rationalized by a significant involvement of the phenyl subsitutents in this transition as supported by TD-DFT calculations (Supplementary Fig. 18).…”

“…In the case of helicene structures, homochiral self-recognition is accepted to be a general trend in noncovalent bonding events 20,21 . In this context, the homochiral supramolecular complexes observed upon encapsulation of [4]-and [5]-carbohelicenes within an inherently chiral PBI cyclophane introduced recently by us extends this empirical result to non-identical molecules with structural analogies by revealing the perfect accommodation of substrates with the same configuration as the adjacent PBIs within a tailored cavity 22 .…”

“…1) begins with the distortion of a PBI chromophore into a chiral π-scaffold. Besides the diagonal or lateral bridging of the 1,7 4,5,22,38 or the 1,12 39,40 bay area positions, respectively, another way to achieve helically twisted PBIs 41 is the steric overcrowding by bulky substituents in the bay position [42][43][44][45] . Accordingly, we started with the fourfold arylation of a PBI in the bay position and a subsequent saponification, which yields the literature known perylene bisanhydride rac-2 as a mixture of atropo-enantiomers 46 .…”

A Terrylene Bisimide based Universal Host for Aromatic Guests to Derive Contact Surface‐Dependent Dispersion Energies

“…[11] Whilst our initial cyclophane designs based on perylene bisimide (PBI) units did not afford the desired open cavities for guest encapsulation due to the strong intermolecular interactions between the larger π-planes of these dyes, [12] in 2015 we finally accomplished the synthesis of the first PBI cyclophane acting as a host for various PAHs. [13] Still, however, due to the restricted length of the PBI moiety the cavity of this and other meanwhile reported PBI cyclophanes [14] remains rather small, enabling only binding of a limited number of guests such as perylene with high affinity as required for photophysical studies on such hostguest complexes in dilute solution. To overcome this deficiency, here we introduce a new cyclophane comprising of larger terrylene bisimide (TBI) moieties.…”

Asymmetric living supramolecular polymerization of an achiral aza-BODIPY dye by solvent-mediated chirality induction and memory

“…In the recent decade, molecular aggregates with supramolecular chirality 1 have gained considerable attention and been investigated widely due to their assembly mechanism 2 and applications, such as in chiral recognition and sensing, 3 supramolecular chiral catalysis, 4 chiral optic and electronic devices, 5 and biomaterials. 6 It has been demonstrated that for π-conjugated molecules, such as porphyrins, 7 oligo( p-phenylene vinylene)s, 8 perylene and naphthalene bisimides, 9 hexabenzocoronenes, 10 etc., supramolecular chirality and structural helicity can be obtained for one-dimensional π-stacks by introducing side chains with a permanent chiral center.…”