Folding-Induced Through-Space Magnetic Interaction of Poly(1,3-phenyleneethynylene)-Based Polyradicals

We synthesized poly­(1,3-phenyleneethynylene)­s bearing galvinoxyl moieties. The absorption ratio of the anion form in 1 M KOH methanol solution between 309 and 294 nm (<i>A</i>₃₀₉/<i>A</i>₂₉₄) decreased with increasing degree of polymerization. The wide-angle X-ray scattering of the powder, which was prepared by precipitation in dilute hydrochloric acid solution from the anion form in 1 M KOH methanol solution, showed a crystalline peak at 2θ = 28°. Polymers in which the chiral diethynyl-1,1′-binaphthyl moiety was inserted into the poly­(1,3-phenyleneethynylene) chain were synthesized, and clear Cotton effects were observed in the absorption region of the galvinoxyl anion chromophore in the CD spectra taken in 1 M KOH–MeOH solution, indicating an excess of one-handed folded helical conformation. A relatively strong antiferromagnetic interaction was observed for the polyradicals prepared by precipitating the anionic form from alkaline methanol solution accompanied with oxidation using aqueous K₃Fe­(CN)₆ solution. These observations suggest that the relatively strong antiferromagnetic interaction of the polyradicals was caused by the close packing between galvinoxyl radicals induced by the formation of the folded helical structure

Subnanoporous Highly Oxygen Permselective Membranes from Poly(conjugated hyperbranched macromonomer)s Synthesized by One-Pot Simultaneous Two-Mode Homopolymerization of 1,3-Bis(silyl)phenylacetylene Using a Single Rh Catalytic System: Control of Their Structures and Permselectivities

Novel well-defined complex polymers, polymers of acetylene-type macromonomers having silylene–vinylene–phenylene–ethynylene hyperbranches, investigated as a new class of subnanoporous oxygen permselective membrane materials, were synthesized very easily by one-pot simultaneous two-mode homopolymerization of a single monomer with a single catalyst. For this “simultaneous polymerization” we synthesized AB₂-type monomers (1,3-bis­(dimethylsilyl)­phenylacetylenes) containing one terminal triple bond and two Si–H groups. The resulting poly­(hyperbranched macromonomer)­s had high molecular weights, low densities, high solubility, and good self-membrane forming ability. They had higher oxygen permselectivities (α = <i>P</i>_O₂/<i>P</i>_N₂) than any other reported polymers having similar oxygen permeabilities (<i>P</i>_O₂). These excellent polymer membranes could be obtained only by the simultaneous polymerization. In the one-pot simultaneous polymerization, the two different modes of polymerizations, i.e., addition polymerization of the triple bond and polyaddition of the triple bond and two SiH groups in the single monomer, occurred simultaneously by using one catalytic system, i.e., [Rh­(norbornadiene)­Cl]₂/various amines. The ratio of the branches (<b>RB</b>), i.e., the addition polymerization and the polyaddition, could be controlled by changing the amine cocatalysts. Their oxygen permselectivities could be adjusted by controlling the polymer structures including <b>RB</b>

Annealing-Induced Circular Dichroism Enhancement in Luminescent Conjugated Polymers with an Intramolecular Stack Structure

Two poly­(diphenylacetylene) derivatives containing identical chiral pinanyl groups on the <i>para</i>- and <i>meta</i>-positions of the side phenyl ring were prepared, and their circular dichroism (CD) and photoluminescence (PL) spectra were compared. The magnitudes of circular polarization (<i>g</i>_CD) of the <i>para</i>- and <i>meta</i>-polymers were determined to be 3.1 × 10^–3 and 1.4 × 10^–3, respectively. The PL quantum yield (PLQY) of the <i>para</i>-polymer was much greater (27.8%) than that of the <i>meta</i>-polymer (2.61%). When the two polymers were annealed at 80 °C in toluene, their CD spectra were remarkably enhanced and reached equilibrium at <i>g</i>_CD values of 9.6 × 10^–3 and 6.0 × 10^–3, respectively. The <i>para</i>-polymer was kinetically more favored for the CD enhancement as known from the fact that the activation energies for the reactions of <i>para</i>- and <i>meta</i>-polymers were determined to be 88 and 187 kJ mol^–1, respectively. The PLQYs of both polymers were unaffected by annealing

Synthesis of <i>Pure</i> Supramolecular Polymers from Poly(substituted Phenylacetylene)s by Highly Selective Photocyclic Aromatization and Their Characterization: Effect of the Structures and Properties of Precursor Covalent Polymers on those of the Resulting <i>Pure</i> Supramolecular Polymers

Several pure supramolecular polymers (SPs) were quantitatively synthesized by highly selective photocyclic aromatization (SCAT reaction) of poly(substituted phenylacetylene)s (CPs). The structures such as the degree of polymerization (DPn) and the one-handed helicities (chiralities) of the main chains of these precursor covalent polymers (CPs) were well-controlled by living or helix-sense-selective polymerizations. We found that the structures and properties of the resulting SPs were strongly influenced by those of the precursor CPs. In other words, some of the structures and properties of CPs were transferred to those of SPs. For example, the CPs with higher DPns yielded the corresponding SPs with higher DPns and strengths, and the CPs with one-handed helical chirality produced the corresponding SPs with enantioselective permeability in the membrane and supramolecular chirality in solution. In addition, since the shapes of solid materials from these CPs were transferred to the resulting SPs with some mechanical strength, they are promising for many practical applications such as membrane permeations

Synthesis of One-Handed Helical Block Copoly(substituted acetylene)s Consisting of Dynamic <i>cis-transoidal</i> and Static <i>cis-cisoidal</i> Block: Chiral Teleinduction in Helix-Sense-Selective Polymerization Using a Chiral Living Polymer as an Initiator

By using a living one-handed helical <i>cis-transoidal</i> poly­(chiral substituted phenylacetylene) as a polymer initiator (poly­(<b>1</b>_n)), helix-sense-selective polymerization (<b>HSSP</b>) of an achiral phenylacetylene <b>2</b> having two hydroxy groups successfully afforded a diblock copoly­(phenylacetylene) (copoly­(<b>1</b>_n/<b>2</b>_m)) consisting of a dynamic one-handed helical <i>cis-transoidal</i> block and a static one-handed helical <i>cis-cisoidal</i> block. The formation of the diblock structure was confirmed by consumption of the chiral initiator, appearance of characteristic CD indicating the one-handed helical <i>cis-cisoidal</i> block, and occurrence of the selective photocylic aromatization reaction in the <i>cis-cisoidal</i> block. Therefore, <b>HSSP</b> has been achieved by using the chiral alkenyl groups in the initiator as a chiral source for the first time. In addition, since the <b>HSSP</b> was achieved in spite of the long distance between the chiral initiation site and the propagating site, chiral teleinduction through the rigid and static one-handed helical <i>cis</i>-cisoidal block based on domino effects was confirmed

Transformer of Achiral Amounts to Chirality: Double Reversal of Enantioselectivity Using a Single Cocatalyst in Asymmetric Polymerization

Chiral compounds play a vital role in our lives because we are made up of chiral polymers. A strict rule of chirality synthesis is “to obtain one enantiomer of a new chiral product, one enantiomer of a chiral source is needed”. If two enantiomers can be synthesized using a single chiral compound, we can both break the above rule and open up a more efficient route to useful chiral materials using a cheaper chiral source. Here we report the first example of double reversals of enantioselectivity in catalytic asymmetric polymerization of achiral monomers using a single isomer of simple chiral compounds as cocatalyst. Furthermore, we achieved this by changing only one achiral condition, that is, the amount of the chiral cocatalyst, without any other changes in the polymerization conditions. As a result, we easily and directly synthesized (+)- or (−)-polymer using a single chiral compound as a cocatalyst

Top-Down Preparation of Self-Supporting Supramolecular Polymeric Membranes Using Highly Selective Photocyclic Aromatization of Cis–Cisoid Helical Poly(phenylacetylene)s in the Membrane State

A novel, highly selective photocyclic aromatization (SCAT) of π-conjugated polymers from phenylacetylene having two hydroxyl groups to exclusively yield a 1,3,5-trisubstituted benzene derivative was developed, and its success was confirmed by ¹H NMR, GPC, and TOF-MS. The SCAT reaction has many unique characteristics. (1) It is a quantitative reaction: it gave only the corresponding cyclic trimer, i.e., a 1,3,5-trisubstituted benzene derivative, quantitatively (100%). No byproducts were produced under the best conditions. (2) It is an intramolecular reaction: it occurred between three adjacent monomer units in one macromolecule. (3) It is a stereospecific and topochemical or template reaction: the reactivity strongly depended on the configuration and conformation of the starting polymer substrates. (4) It is a photoreaction: high selectivity (100%) was observed only by the use of visible light irradiation, not by heating. (5) It is a solid-state reaction: high selectivity (100%) was observed only in the solid state, not in solution. <i>In addition</i>, (6) the resulting cyclic trimers could form a self-supporting membrane, despite their low molecular weights. This new approach resulted in a new class of supramolecular polymers consisting of a 1,3,5-trisubstituted benzene derivative, numbers of which were linearly linked by hydrogen bonds and stacked benzene derivatives. Since SCAT has such high selectivities and is useful for the preparation of a self-supporting supramolecular polymer membrane, many applications can be expected

Asymmetric Restriction of Intramolecular Rotation in Chiral Solvents

Commercially available molecular rotor (MR) compounds were recrystallized using chiral monoterpenes as solvents. The resulting crystals exhibited large circular dichroism signals with opposing signs according to the handedness of the chiral solvent used. X-ray crystallographic analysis showed that the chirality originated from asymmetric restriction of intramolecular rotation in the crystals. The crystals were also highly emissive due to restricted bond rotation, while solutions of the materials were almost nonemissive. The solvent-to-MR chirality transfer approach to crystallization discussed herein should be a convenient, universal way to obtain highly emissive chiral crystals