Dynamic‐to‐Static Planar Chirality Conversion in Pillar[5]arenes Regulated by Guest Solvents or Amplified by Crystallization

Abstract

Controlling dynamic chirality and memorizing the controlled chirality are important. Chirality memory has mainly been achieved using noncovalent interactions. However, in many cases, the memorized chirality arising from noncovalent interactions is erased by changing the conditions such as the solvent and temperature. In this study, the dynamic planar chirality of pillar[5]arenes was successfully converted into static planar chirality by introducing bulky groups through covalent bonds. Before introducing the bulky groups, pillar[5]arene with stereogenic carbon atoms at both rims existed as a pair of diastereomers, and thus showed planar chiral inversion that was dependent on the chain length of the guest solvent. The pS and pR forms, regulated by guest solvents, were both diastereomerically memorized by introducing bulky groups. Furthermore, the diastereomeric excess was amplified by crystallization of the pillar[5]arene. The subsequent introduction of bulky groups yielded pillar[5]arene with an excellent diastereomeric excess (95 % de).

Insights into the Self‐Filling Effects of Branched Isopropyl Groups on the Conformational and Supramolecular Properties of Isopropoxyprism[6]arene

“…In details, in agreement with the solid state structure of PrS[6] iPr in Figure 2, the doublet at −1.44 ppm is attributable to inward oriented methyl groups (Figures 2 and 3) while the diastereotopic CH 3 ‐doublet at 0.38 ppm is outward oriented with respect to the PrS[6] iPr cavity. The presence of these diastereotopic resonances for the OCH( CH 3 ) 2 groups of PrS[6] iPr is due to the planar chirality of the macrocycle [18–22] . In fact, the PrS[6] iPr shows six planes of chirality which are coplanar with the 2,6‐dialkoxynaphthalene rings and the bridged‐methylene carbons at the 1/5 ring positions.…”

“…The presence of these diastereotopic resonances for the OCH(CH 3 ) 2 groups of PrS [6] iPr is due to the planar chirality of the macrocycle. [18][19][20][21][22] In fact, the PrS[6] iPr shows six planes of chirality which are coplanar with the 2,6-dialkoxynaphthalene rings and the bridged-methylene carbons at the 1/5 ring positions. In fact, the centrosymmetric crystal structure of PrS [6] iPr is composed of a racemic mixture of chiral macrocyclic molecules, in which naphthalene moieties adopt all-pS (or all-pR), orientation.…”

Alignment and Dynamic Inversion of Planar Chirality in Pillar[n]arenes

“…In 2023, Ogoshi and co‐workers designed pillar[5]arene 29 with 2‐( S )‐methylbutoxy moieties on four benzene units and alkyl azide groups on the other benzene unit (Figure 10b). [79] With eight identical chiral side chains, 29 exhibits almost the same solvent‐dependent chirality enrichment characteristics as that of 24Me . 29 mainly adopts the pR ‐ and pS ‐forms in dicholoroethane and dibromobutane, respectively.…”

Functionalization of pillar[n]arenes towards optically responsive systems via host–guest interactions

“…The dissymmetry factor of luminescence |g abs | reached 1.28 Â 10 À2 , and was comparable to those of fixed planar chiral pillar [5]arene based-CPL materials. 97,119,124…”

“…6b). 119 The dihaloalkane guest solvents regulated planar chirality as in the case of H22 . Subsequent CuAAC click reactions to the two azide groups on H23 with a bulky propargyl derivative resulted in planar chirality fixation.…”