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.

Acceptor-Induced Fluorescence of Phenolic Polymers Based on Triphenylamine Derivatives.

Conductive polymers facilitate the electrical current flow through the transfer of electrons and holes. They show promise for novel photo-functional materials in photovoltaics. However, substantial electrostatic interactions between electron donors and acceptors induce polymer aggregation, limiting moldability and conductivity.

Imaging single CaMKII holoenzymes at work by high-speed atomic force microscopy.

Ca/calmodulin-dependent protein kinase II (CaMKII) plays a pivotal role in synaptic plasticity. It is a dodecameric serine/threonine kinase that has been highly conserved across metazoans for over a million years. Despite the extensive knowledge of the mechanisms underlying CaMKII activation, its behavior at the molecular level has remained unobserved.

Orientational Control of Circularly Polarized Luminescence from Pyrene Clusters by Using a DNA Scaffold.

Invited for the cover of this issue is the group of Hiromu Kashida and Hiroyuki Asanuma at Nagoya University and co-workers. The image depicts the orientation dependence of circularly polarized luminescent. Read the full text of the article at 10.

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.

Orientational Control of Circularly Polarized Luminescence from Pyrene Clusters by Using a DNA Scaffold.

We have investigated the chiroptical activities of pyrene clusters incorporated within a DNA duplex. Three pyrene derivatives were prepared on d-threoninol linkers to allow incorporation within a DNA strand. DNA scaffolds containing dimers, tetramers, and hexamers of the pyrene derivatives were prepared.

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).

Polypseudorotaxanes constructed from pillar[5]arenes and polyamides by interfacial polymerization.

Polypseudorotaxanes constructed from pillar[5]arene rings and polyamide chains were successfully synthesized by interfacial polymerization between diamines and dicarbonyl chlorides in the presence of pillar[5]arene. The dicarbonyl chloride length and the assocation constants of dicarbonyl chloride-pillar[5]arene complexes were important factors in producing polypseudorotaxanes with high cover ratio of pillar[5]arene rings.

Reversible "On/Off" Chiral Amplification of Pillar[5]arene Assemblies by Dual External Stimuli.

We report dual-stimuli, thermo- and photostimuli, responsive chiral assemblies, of planar-chiral pillar[5]arenes with azobenzene groups on their rims. The azobenzene-substituted planar-chiral pillar[5]arenes were synthesized by copper(I)-catalyzed alkyne-azide cycloaddition "click" reaction of azide-substituted planar-chiral pillar[5]arenes containing or stereogenic carbon atoms with an alkyne-substituted azobenzene. These decaazides with stereogenic carbons could act as starting points for a large library of planar-chiral pillar[5]arenes.

A Pyrene-Modified Serinol Nucleic Acid Nanostructure Converts the Chirality of Threoninol Nucleic Acids into Circularly Polarized Luminescence Signals.

Herein is reported a circularly polarized luminescent (CPL) probe that can respond to the chirality of nucleic acids. An achiral nanostructure was prepared by the hybridization of symmetric serinol nucleic acid (SNA) containing pyrene-modified residues. When chiral oligomers that were complementary to the SNA were added, they induced helicity into the SNA nanowire.

Supramolecular exfoliation of layer silicate clay by novel cationic pillar[5]arene intercalants.

Clays are multi-layered inorganic materials that can be used to prepare nanocomposite fillers. Because the multi-layered structure is thermodynamically stable, it is difficult to change a multi-layered material into single layers to improve its dispersity. Previously, clays were modified with dodecylammonium cations to promote complexation with nylon 6, nylon 66, polypropylene, polyethylene, polystyrene, and polycaprolactone to increase the mechanical strength (and/or thermal stability) of the composite material; however, complete exfoliation could not be achieved in these composites.

The carbonization of aromatic molecules with three-dimensional structures affords carbon materials with controlled pore sizes at the Ångstrom-level.

Carbon materials with controlled pore sizes at the nanometer level have been obtained by template methods, chemical vapor desorption, and extraction of metals from carbides. However, to produce porous carbons with controlled pore sizes at the Ångstrom-level, syntheses that are simple, versatile, and reproducible are desired. Here, we report a synthetic method to prepare porous carbon materials with pore sizes that can be precisely controlled at the Ångstrom-level.

Thermally Responsive Poly(ethylene oxide)-Based Polyrotaxanes Bearing Hydrogen-Bonding Pillar[5]arene Rings.

Invited for the cover of this issue are Tomoki Ogoshi and co-workers at Kyoto University, Kanazawa University and Tokyo University of Agriculture and Technology. The image depicts musical notation to represent hydrogen bond networks and poly(ethylene oxide) chains. Read the full text of the article at 10.

Thermally Responsive Poly(ethylene oxide)-Based Polyrotaxanes Bearing Hydrogen-Bonding Pillar[5]arene Rings*.

Poly(ethylene oxide)s (PEOs) are useful polymers with good water solubility, biological compatibility, and commercial availability. PEOs with various end groups were threaded into pillar[5]arene rings in a mixture of water and methanol to afford pseudopolyrotaxanes. Corresponding polyrotaxanes were also constructed by capping COOH-terminated pseudopolyrotaxanes with bulky amines, in which multiple hydrogen bonds involving the pillar[5]arene OH groups were critically important to prevent dethreading.

Pillar[6]arene acts as a biosensor for quantitative detection of a vitamin metabolite in crude biological samples.

Metabolic syndrome is associated with obesity, hypertension, and dyslipidemia, and increased cardiovascular risk. Therefore, quick and accurate measurements of specific metabolites are critical for diagnosis; however, detection methods are limited. Here we describe the synthesis of pillar[n]arenes to target 1-methylnicotinamide (1-MNA), which is one metabolite of vitamin B3 (nicotinamide) produced by the cancer-associated nicotinamide N-methyltransferase (NNMT).

A light-operated pillar[6]arene-based molecular shuttle.

A molecular shuttle comprising a pillar[6]arene macrocyclic ring and an axle with two equal-energy-level stations connected by an azobenzene unit was synthesised. The E isomer of the azobenzene functioned as "open gate", allowing the pillar[6]arene ring to rapidly shuttle back-and-forth between the two stations. Ultraviolet irradiation induced photo-isomerisation of the azobenzene from E to Z form.

High Refractive-Index Hybrids Consisting of Water-Soluble Matrices with Bipyridine-Modified Polyhedral Oligomeric Silsesquioxane and Lanthanoid Cations.

We report high refractive-index (RI) films composed of polyhedral oligomeric silsesquioxane (SSQ) matrices and various lanthanoid cations. The SSQ matrices were constructed from octaammonium SSQ by connecting with bipyridine dicarboxylic acid, which is expected to capture cations. By modulating the feed ratio between SSQ and dicarboxylic acid, the series of the SSQ matrices were obtained with variable cross-linking ratios among the SSQ units.

Holding of planar chirality of pillar[5]arene by kinetic trapping using host-guest interactions with achiral guest solvents.

We report a solvent-dependent switching and holding of planar chirality of pillar[5]arene with stereogenic carbons at both rims by host-guest complexation with achiral guest solvents. The planar chirality could be held for a given length of time at 25 °C in long linear guest solvents by kinetic trapping through host-guest complexation. The kinetic trapping worked at 25 °C, but not at 60 °C, thus a planar-chiral inversion using kinetic trapping based on host-guest complexation in the long linear solvents was demonstrated.

Halogen-sensitive solvatochromism based on a phenolic polymer of tetraphenylethene.

Herein, we describe the successful preparation of a methylene-bonded tetraphenylethene polymer using a phenolic-resin synthesis protocol. Our novel phenolic polymer showed solvatochromism in response to halogenated organic solvents. Solvatochromism is induced by halogen/π interactions between the polymer and the organic halide.

Obvious vapochromic color changes of a pillar[6]arene containing one benzoquinone unit with a mechanochromic change before vapor exposure.

We developed a color changeable aromatic vapor detection system by combining the mechanochromism and vapochromism of pillar[6]arene containing one benzoquinone unit. The color of pillar[6]arene solid was changed by mechanochromism before vapor exposure. Different aromatic vapors then induced an obvious vapochromic color change from dark red to light orange or vice versa.

Molecular weight fractionation by confinement of polymer in one-dimensional pillar[5]arene channels.

Confinement of polymers in nano-spaces can induce unique molecular dynamics and properties. Here we show molecular weight fractionation by the confinement of single polymer chains of poly(ethylene oxide) (PEO) in the one-dimensional (1D) channels of crystalline pillar[5]arene. Pillar[5]arene crystals are activated by heating under reduced pressure.

Control of Circularly Polarized Luminescence by Orientation of Stacked π-Electron Systems.

Planar chiral building blocks based on 4,7,12,15-tetrasubstituted [2.2]paracyclophanes were obtained via a synthetic route involving an optical resolution step. Planar chiral enantiomers, comprising two fluorophores that were stacked to form a V-shaped higher-ordered structure, were synthesized from these building blocks.

Guest Vapor-Induced State Change of Structural Liquid Pillar[6]arene.

State change is a key phenomenon in materials science. We report the first observation of vapor-responsive reversible structural liquid-to-solid and solid-to-structural liquid state changes. We observed that a macrocyclic compound, a pillar[6]arene derivative bearing 12 n-hexyl substituents, is a room temperature structural liquid with unique properties.