Diastereoselective Polypseudorotaxane Formation with Planar Chiral Pillar[5]arenes via Co-crystallization Processes.

As the number of chiral ring molecules in chiral polyrotaxane increases, the number of possible stereoisomers exponentially increases. Consequently, the selective synthesis of a specific stereoisomer becomes much more challenging. To address this problem, we co-crystallized poly(ethylene glycol) and a diastereomeric ring molecule, pillar[5]arene, in the solid state.

Helical-Sense Matching Facilitates Supramolecular Copolymerization of Helical-Chiral Pillar[5]arenes.

Supramolecular polymerization using two-dimensional π-conjugated chiral monomers has been mainly demonstrated because the supramolecular polymerization can be controlled by stereocommunication through π-π stacking between the two-dimensional chiral monomers. We herein report supramolecular copolymerization utilizing three-dimensional pentahedrons with twisted helical chirality through different combinations of helical-chiral acidic and basic pillar[5]arenes as comonomers. In this case, helical-sense matching is key to facilitating the supramolecular copolymerization.

Self-Inclusion Complexation of Electron-Accepting Guest into Electron-Donating Cyclic Host by Photoexcitation.

Self-inclusion complexes consisting of host-guest conjugates are one of the unique supramolecular structures because they form in-state and out-state depending on the external stimuli. Despite many reports of the stimuli-responsive self-inclusion complex formation, study of the structural relaxation from out-state to in-state by photoexcitation has been unexplored. Herein, we report that an electron-donating host and an electron-accepting guest conjugate exhibits the structural relaxation from out-state to in-state by photoexcitation.

Exciplex Formation by Complexation of an Electron-Accepting Guest in an Electron-Donating Pillar[5]arene Host Liquid.

We present a novel system, a liquid-state pillar[5]arene decorated with tri(ethylene oxide) chains, that brings electron-donor and electron-acceptor molecules into proximity for efficient exciplex formation. The electron-accepting guests exhibit a blue-purple emission from a localized excited state upon excitation in common solvents. However, directly dissolving the guests in the electron-donating pillar[5]arene liquid (a bulk system) results in visible green emission from the formed exciplexes.

Alkoxylated Fluoranthene-Fused [3.3.3]Propellanes: Facile Film Formation against High π-Core Content.

Solid-state assembling modes are as crucial as the chemical structures of single molecules for real applications. In this work, solid-state structures and phase-transition temperatures are investigated for a series of fluoranthene-fused [3.3.

Synthesis of Regioregular and Random Boron-Fused Azomethine Conjugated Polymers for Film Morphology Control.

Regioregular and random conjugated polymers based on a boron-fused azomethine unit were synthesized by Sonogashira-Hagihara cross coupling reaction. Although these polymers exhibited similar optical properties in the solution states, a distinct difference was observed in the aggregation forming ability in the film states; scanning electron microscope (SEM) observation indicated the existence of fiber-like aggregates in the spin-coated film of the regioregular polymer, while regiorandom polymer showed no aggregate in the film state. Accordingly, the UV-vis absorption spectrum of the regioregular polymer showed an increased shoulder peak due to the aggregate formation, whereas the random one showed no change.

Efficient synthesis and unit-selective π-extension of π-fused [4.3.3]propellane as a chiral building block.

A three-dimensional skeleton, π-fused [4.3.3]propellane, was constructed and derivatized by selective π-extension at the two naphthalene units.

Per-Arylation of Pillar[]arenes: An Effective Tool to Modify the Properties of Macrocycles.

Installation of various substituents is a reliable and versatile way to alter the properties of macrocyclic molecules, but high-yield and controlled methods are not always available especially for multifold reactions. Herein, we report 10- and 12-fold introduction of aryl substituents onto both rims of cylinder-shaped pillar[]arenes, which usually have alkoxy substituents slanting to the cylinder axes. Although alkoxy pillar[5]arenes exist as -symmetric enantiomeric pairs, arylated pillar[5]arenes provide crushed single-crystal structures and stereoisomerism including -symmetric conformations depending on the aryl groups.

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

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.

A Twisted Chiral Cavitand with 5-Fold Symmetry and Its Length-Selective Binding Properties.

Controlling bottom-up syntheses from chiral seeds to construct architectures with specific chiralities is currently challenging. Herein, a twisted chiral cavitand with 5-fold symmetry was constructed by bottom-up synthesis using corannulene as the chiral seed and pillar[5]arene as the chiral wall. After docking between the seed and the wall, their dynamic chiralities ( and ) are fixed.

Real-time chirality transfer monitoring from statistically random to discrete homochiral nanotubes.

Real time monitoring of chirality transfer processes is necessary to better understand their kinetic properties. Herein, we monitor an ideal chirality transfer process from a statistically random distribution to a diastereomerically pure assembly in real time. The chirality transfer is based on discrete trimeric tubular assemblies of planar chiral pillar[5]arenes, achieving the construction of diastereomerically pure trimers of pillar[5]arenes through synergistic effect of ion pairing between a racemic rim-differentiated pillar[5]arene pentaacid bearing five benzoic acids on one rim and five alkyl chains on the other, and an optically resolved pillar[5]arene decaamine bearing ten amines.

Cyclic arrays of five pyrenes on one rim of a planar chiral pillar[5]arene.

Spatial arrangement of multiple planar chromophores is an emerging strategy for molecule-based chiroptical materials easy and systematic synthesis. We attached five pyrene planes to a chiral macrocycle, pillar[5]arene, producing a set of chiroptical molecules in which pyrene-derived absorption and emission were endowed with dissymmetry by effective transfer of chiral information. The chiroptical response was dependent on linker structures and substituted patterns because of variable interactions between pyrene units.

Room-Temperature Ring-Opening Polymerization of δ-Valerolactone and ϵ-Caprolactone Caused by Uptake into Porous Pillar[5]arene Crystals.

Confined space provides a reaction platform with altered reaction rate and selectivity compared with a homogeneous solution. In this work, porous phenolic pillar[5]arene crystals were used as a reaction space to promote and perturb equilibrium between lactones and their corresponding polyesters. Immersion of porous pillar[5]arene crystals in liquid lactones induced ring-opening polymerization of δ-valerolactone and ϵ-caprolactone at room temperature because the phenolic hydroxy groups have catalytic activity via hydrogen bonds and the pillar[5]arene cavities prefer linear guests.

Discrete Macrocycles with Fixed Chirality and Two Distinct Sides: Dipole-Dependent Chiroptical Response.

Control of symmetry is fundamental in molecular design with aimed properties. Herein we report a set of chiroptical C -symmetric molecules with variable dipolar structures based on a rim-differentiated cylindrical macrocycle, pillar[5]arene. Incorporation of electron-withdrawing ester groups formed an explicit two-sided structure, leading to increase in response wavelength and luminescence efficiency.

CPL on/off control of an assembled system by water soluble macrocyclic chiral sources with planar chirality.

Herein, we report the synthesis and planar chiral properties of a pair of water-soluble cationic pillar[5]arenes with stereogenic carbons. Interestingly, although units of the molecules were rotatable, only one planar chiral diastereomer existed in water in both cases. As a new type of chiral source, these molecules transmitted chiral information from the planar chiral cavities to the assembly of a water-soluble extended π-conjugated compound, affording circularly polarized luminescence (CPL).

Noncovalently bound and mechanically interlocked systems using pillar[]arenes.

Pillar[]arenes are pillar-shaped macrocyclic compounds owing to the methylene bridges linking the para-positions of the units. Owing to their unique pillar-shaped structures, these compounds exhibit various excellent properties compared with other cyclic host molecules, such as versatile functionality using various organic synthesis techniques, substituent-dependent solubility, cavity-size-dependent host-guest properties in organic media, and unit rotation along with planar chiral inversion. These advantages have enabled the high-yield synthesis and rational design of pillar[]arene-based mechanically interlocked molecules (MIMs).

State- and water repellency-controllable molecular glass of pillar[5]arenes with fluoroalkyl groups by guest vapors.

Molecular glasses are low-molecular-weight organic compounds that are stable in the amorphous state at room temperature. Herein, we report a state- and water repellency-controllable molecular glass by -alkane guest vapors. We observed that a macrocyclic host compound pillar[5]arene with the CF fluoroalkyl groups changes from the crystalline to the amorphous state (molecular glass) by heating above its melting point and then cooling to room temperature.