Tsukasa Maruyama

Unique optical and electrochemical properties of π-conjugated electrically conducting copolymers consisting of electron-withdrawing pyridine units and electron-donating thiophene units

Electrically conducting π-conjugated copolymers consisting of π-excessive thiophene-2,5-diyl and π-deficient pyridine-2,5-diyl monomer units show a unique cyclic voltammogram with an unusually large potential difference between the doping and the undoping peaks, and their electronic and fluorescence spectra support occurrence of intramolecular charge transfer showing absorption and fluorescence peaks at lower energy compared with those of the corresponding homopolymers.

Microsphere synthesis of polypyrrole by oxidation polymerization

Abstract Polymer microspheres were synthesized by oxidation polymerization of pyrrole (Py) with functional poly(vinyl alcohol) having pendent Py groups (PVA-P) or poly(vinyl alcohol) (PVA) as an emulsifier in various solvent media. In this polymerization system, PVA-P acted not only as a comonomer but also as a stabilizer. The diameter (submicrometre range) of the polymer microspheres decreased with increasing PVA concentration in the medium. Polypyrrole (PPy) microspheres had a very narrow particle size distribution ( D W / D n . The particles stabilized with PVA-P were smaller than the corresponding particles stabilized with PVA. The use of PVA-P as an emulsifier was favourable to the formation of micelles with Py monomers. The electrical conductivity of the PPy particles was in the range 10−5–10−1 S cm−1, depending on the amount of dopant.

Poly(4,4′-dialkyl-2,2′-bithiazole-5,5′-diyl). New electron-withdrawing π-conjugated polymers consisting of recurring five-membered rings

New π-conjugated polymers consisting of recurring electron-withdrawing five-membered (thiazole) rings, poly(4,4′-dialkyl-2,2′-bithiazole-5,5′-diyl), are prepared and are found to be electrochemically reduced (or n-doped) at ca.–2. 0 V vs. Ag/Ag+.

Preparation of π-conjugated polythiazoles and their electrically conducting properties

Abstract Poly(thiazole-2,5-diyl) (PTz), poly(4-methylthiazole-2,5-diyl) (PMeTz) and poly(4,4′-dimethyl-2,2′-bithiazole-5,5′-diyl) (PMeBTz) are synthesized by dehalogenation polycondensation of the corresponding dibromothiazoles with zero-valent nickel complexes. PTz and PMeTz are soluble in formic acid and trifluoroacetic acid, whereas PMeBTz is soluble in trifluoroacetic acid. PTz and PMeBTz have weight-average molecular weights ( M w ) of 5.9 × 10 4 and 3.2 × 10 3 , respectively, as determined by a light scattering method. The UV-Vis spectra of PTz, PMeTz and PMeBTz show π-π ∗ absorption peaks at 421 nm (in formic acid), 420 nm (in formic acid) and 425 nm (in trifluoroacetic acid), respectively. These absorption peaks are shifted to longer wavelength compared with that (λ max = 233 nm) of thiazole. Sodium doping of polythiazoles affords semiconducting materials with conductivity (σ) values of an order of 10 −4 S cm −1 .

New copper complex with π-conjugated electrically conductive polymer chelating ligand, poly(6,6′-dialkyl-2,2′-bipyridine-5,5′-diyl). Preparation and optical and electrochemical properties of the complex

Abstract π-Conjugated electrically conducting polymer chelate ligands, poly(6,6′-dimethyl-2,2′-bipyridine-5,5′-diyl) (P6MeBpy) and poly(6,6′-dihexyl-2,2′-bipyridine-5,5′-diyl) (P6HexBpy), react with [Cu(CH3CN)4]X (X = BF4, ClO4) to give the corresponding semiconductive copper (I) complexes. The P6HexBpy-CuBF4 complex exhibits an MLCT absorption at 469 nm (ϵ = 3300 M−1 cm−1). The cyclic voltammogram of a film of the P6HexBpy-CuBF4 complex laid on a Pt electrode shows reversible redox peaks with an E0 value of 0.59 V versus Ag+/Ag due to a Cu(II)/(I) couple, whereas, in the reduction region, the film of the complex exhibits an electrochemically active cycle at E0 of −1.84 V attributable to a Cu(I)/(0) couple. The redox process at −1.84 V is accompanied by a color change of the film from orange to dark red. These UV-Vis and electrochemical data of the P6HexBpy-CuBF4 complex are discussed by comparing them with data of monomeric model complexes, [Cu(bpy)2]BF4, [Cu(dmebpy)2]BF4 and [Cu(dhexbpy)2]BF4 (dmebpy = 6,6′-dimethyl-2,2′-bipyridine; dhexbpy = 6,6′-dihexyl-2,2′-bipyridine).

Photochemical control of conductivity of polythiophenes with photochromic moieties

The synthesis, optical and electrical properties of azobenzene-substituted polythiophene derivatives at the 3-position are reported: one without flexible spacer (PT0) and the other with a hexamethylene spacer (PT6). Photoirradiation of PT6 at 366 nm caused trans-cis isomerization of the azobenzene moiety and this photochromic reaction induced a change in conductivity of the thin film of PT6: the conductivity was 1.1×10 –7 S cm –1 before irradiation and 8.3×10 –7 S cm –1 after photoirradiation. After annealing, the conductivity of the film returned to the initial value. The conductivity of a compound without the azobenzene moiety, α-terthienyl (αT3), showed no change on photoirradiation at 366 nm.

Ruthenium and nickel complexes of a π-conjugated electrically conducting polymer chelate ligand, poly(2,2′-bipyridine-5,5′-diyl), and their chemical and catalytic reactivity

Poly(2,2′-bipyridine-5,5′-diyl)(PBpy), a π-conjugated electrically conducting chelate polymer, forms electrochemically active complexes with Ru and Ni; a cyclic voltammogram of the Ru-complex shows redox peaks which are accounted for by assuming electron exchange between the Ru species through the polymer backbone, and a RuCl3–PBpy system serves as an excellent catalyst for photoevolution of hydrogen in an aqueous medium.

Excimer-like emission from linear π-conjugated poly(pyridine-2,5-diyl)

π-Conjugated poly(pyridine-2,5-diyl) and poly(2,2′-bipyridine-5,5′-diyl) give rise to fluorescence in formic acid solutions, in the solid state (film), and in an adduct with poly(vinyl alcohol); the fluorescence in the solid state, in the adduct with poly(vinyl alcohol), and in the formic acid solution with relatively high concentration of the polymer is interpreted by assuming excimer formation.

Preparation and optical properties of soluble π-conjugated poly(aryleneethynylene) type polymers

π-Conjugated poly(aryleneethynylene) type polymers [graphic omitted]CC–Ar–CC–Ar′[graphic omitted]-n(Ar and/or Ar′= pyridine-2,5-diyl or alkyl-substituted arylene) synthesized by a palladium-catalysed coupling reaction are soluble in organic solvents and processable to make good thin films by casting, have large refractive index increment (Δn/Δc= 0.29–0.38), and exhibit photoluminescence as well as fairly strong third harmonic generation, χ(3) value of about 10–10 esu.

N-Oxides and N-ylides of π-conjugated poly(arylene)s. Preparation and properties of the polymers

Treatment of poly(pyridine-2,5-diyl) PPy, poly(quinoline-2,6-diyl) P(2,6-Q), and poly(naphthyridine-2,6-diyl) P(2,6-N) with H2O2 in acetic acid gives quantitatively N-oxidized products of the polymers, PPy-ox, P(2,6-Q)-ox, and P(2,6-N)-diox, respectively. π-π∗ absorption bands of the original polymers show a hypsochromic shift by 35–50 nm by the N-oxidation. Treatment of PPy and P(2,6-Q) with tetracyanoethylene oxide affords N-ylidated products with a 10–15% degree of N-ylidation. The N-oxidized and ylidated polymers undergo electrochemical reduction in a range of about −1.7 to −2.2V vsAgAg+. The electrochemical reduction is accompanied by colour change, and colours of the reduced polymers are considerably different from those of the original polymers (e.g. PPy). The N-oxidized and -ylidated polymers have a d.c. electrical conductivity of 2.8 × 10−7−3.4 × 10−6 S cm−1.