An Electrochromic Nanostructured Liquid Crystal Consisting of π-Conjugated and Ionic Moieties

An Electrochromic Nanostructured Liquid Crystal Consisting of π-Conjugated and Ionic Moietie

Glass-Forming Chiral Liquid Crystalline Dimers Based on an Oligo(phenylenevinylene) Unit Exhibiting Circularly Polarized Photoluminescence

Oligo­(p-phenylenevinylene)-based chiral nematic liquid crystals were synthesized. Mixtures of dimeric and monomeric materials exhibited a glassy chiral nematic phase at room temperature, and the reflection band was tunable from near UV to near IR areas by the temperature and mixing ratio of the chiral nematic materials. The reflection band could be tuned to cover the emission band of the oligo­(p-phenylenevinylene) chromophores completely, resulting in the circularly polarized fluorescence with the dissymmetric factor exceeding 1.4. The reflection band could be immobilized by cooling film samples of the mixtures in ice water. The dissymmetric factor of the glassy chiral nematic films exceeded 1.3 at room temperature. From the film samples of the S-form of the chiral nematic liquid crystals emitted left-handed circularly polarized light while right-handed circularly polarized light was enhanced at the edge of the reflection band due to the Purcell effect

Room Temperature Liquid Fullerenes: An Uncommon Morphology of C₆₀ Derivatives

Room temperature liquid C60 derivatives bearing a 2,4,6-trialkyloxyphenyl branch show a dramatic decrease in viscosity with an increase in the length of the alkyl chains. This feature, when combined with electrochemical activities similar to those of pristine C60 and relatively high charge carrier mobility, makes them an extremely attractive novel carbon material for future applications in materials science

Nanostructured Liquid Crystals Combining Ionic and Electronic Functions

New molecular materials combining ionic and electronic functions have been prepared by using liquid crystals consisting of terthiophene-based mesogens and terminal imidazolium groups. These liquid crystals show thermotropic smectic A phases. Nanosegregation of the π-conjugated mesogens and the ionic imidazolium moieties leads to the formation of layered liquid-crystalline (LC) structures consisting of 2D alternating pathways for electronic charges and ionic species. These nanostructured materials act as efficient electrochromic redox systems that exhibit coupled electrochemical reduction and oxidation in the ordered bulk states. For example, compound 1 having the terthienylphenylcyanoethylene mesogen and the imidazolium triflate moiety forms the smectic LC nanostructure. Distinct reversible electrochromic responses are observed for compound 1 without additional electrolyte solution on the application of double-potential steps between 0 and 2.5 V in the smectic A phase at 160 °C. In contrast, compound 2 having a tetrafluorophenylterthiophene moiety and compound 3 having a phenylterthiophene moiety exhibit irreversible cathodic reduction and reversible anodic oxidation in the smectic A phases. The use of poly(3,4-ethylenedioxythiophene)−poly(4-styrene sulfonate) (PEDOT−PSS) as an electron-accepting layer on the cathode leads to the distinct electrochromic responses for 2 and 3. These results show that new self-organized molecular redox systems can be built by nanosegregated π-conjugated liquid crystals containing imidazolium moieties with and without electroactive thin layers on the electrodes

Palladium-Catalyzed C−H Homocoupling of Bromothiophene Derivatives and Synthetic Application to Well-Defined Oligothiophenes

Synthesis of oligothiophenes of well-defined structures that possess 2−8 thiophene units is performed with a new synthetic strategy involving C−H homocoupling of bromothiophenes and cross-coupling with organostannanes. Tolerance of the carbon−bromine bond to the palladium-catalyzed C−H homocoupling results in oligothiophenes bearing C−Br bonds at the terminal thiophene rings, which allow further transformation by the catalysis of a transition-metal complex

Thermally Induced Self-Doping of π‑Conjugated Polymers Bearing a Pendant Neopentyl Sulfonate Group

A regioregular head-to-tail (HT)-type polythiophene was synthesized by the deprotonative nickel-catalyzed cross-coupling polymerization of 2-chlorothiophene bearing a neopentyl benzenesulfonate group at the 3-position. The obtained HT-regioregular polymer was found to dissolve in chloroform or THF, while it became soluble in water upon heating at 185 °C for 10 min by the liberation of the protected neopentyl group. The thin film of the polymer showed a remarkable improvement in conductivity of ca. 103 times before/after heating, suggesting the thermally induced intramolecular doping of polythiophene by the formed sulfonic acid at the side chain. The related doping was also observed in a poly­(phenylacetylene) derivative, which was synthesized by rhodium-catalyzed polymerization. Copolymerization of such thiophene- and acetylene-bearing neopentyl sulfonate with 3-alkylthiophene and phenylacetylene, respectively, produced the corresponding statistical copolymers, demonstrating the formal self-doping of poly­(3-alkylthiophene) and poly­(phenylacetylene)

Electron Transport and Electrochemistry of Mesomorphic Fullerenes with Long-Range Ordered Lamellae

Electron Transport and Electrochemistry of Mesomorphic Fullerenes with Long-Range Ordered Lamella

Enhanced Circularly Polarized Luminescence by a Homochiral Guest–Host Interaction in Gyroidal MOFs, [Ru(bpy)₃] [M₂(ox)₃] (bpy = 2,2′-Bipyridyl, ox = Oxalate, M = Zn, Mn)

We report the circularly polarized luminescence (CPL) for [Ru­(bpy)3]­I2 (1) and [Ru­(bpy)3]­[M2(ox)3] (M = Zn (2), Mn (3)). Whereas compound 1 is a simple salt of [Ru­(bpy)3]2+, 2 and 3 are MOFs in which the chiral [Ru­(bpy)3]2+ ions are encapsulated in a homochiral gyroidal skeleton of [M2(ox)3]2–. Whereas the solution of 1 exhibited weak CPL with a luminescence dissymmetry factor of |glum| ∼ 10–4, the CPL was significantly enhanced in solid-state 1–3 with |glum| = 2 × 10–2 for 1, 4 × 10–2 for 2, and 1 × 10–1 for 3. The enhanced CPL in 3 was attributable to an energy transfer between the homochiral guest and host in 3

Enhanced Circularly Polarized Luminescence by a Homochiral Guest–Host Interaction in Gyroidal MOFs, [Ru(bpy)₃] [M₂(ox)₃] (bpy = 2,2′-Bipyridyl, ox = Oxalate, M = Zn, Mn)

We report the circularly polarized luminescence (CPL) for [Ru­(bpy)3]­I2 (1) and [Ru­(bpy)3]­[M2(ox)3] (M = Zn (2), Mn (3)). Whereas compound 1 is a simple salt of [Ru­(bpy)3]2+, 2 and 3 are MOFs in which the chiral [Ru­(bpy)3]2+ ions are encapsulated in a homochiral gyroidal skeleton of [M2(ox)3]2–. Whereas the solution of 1 exhibited weak CPL with a luminescence dissymmetry factor of |glum| ∼ 10–4, the CPL was significantly enhanced in solid-state 1–3 with |glum| = 2 × 10–2 for 1, 4 × 10–2 for 2, and 1 × 10–1 for 3. The enhanced CPL in 3 was attributable to an energy transfer between the homochiral guest and host in 3