Yasuhito Miyoshi

Rechargeable Batteries Driven by Redox Reactions of Mn12 Clusters with Structural Changes: XAFS Analyses of the Charging/Discharging Processes in Molecular Cluster Batteries

Molecular clusters such as the Mn12 cluster (Mn12) can be used as a cathode-active material in Li batteries. X-ray absorption fine structure studies on the cathode materials in Mn12 molecular cluster batteries demonstrated that the charging/discharging processes include four-electron-redox reaction of Mn12 with a significant change in its molecular structure.

Crystal Structure, Spin Polarization, Solid-State Electrochemistry, and High n-Type Carrier Mobility of a Paramagnetic Semiconductor: Vanadyl Tetrakis(thiadiazole)porphyrazine

We report the synthesis, crystal structure, and magnetic, electrochemical, and carrier-transport properties of vanadyl tetrakis(thiadiazole)porphyrazine (abbreviated as VOTTDPz) with S = ½. X-ray crystal analysis reveals two polymorphs, the α and β forms; the former consists of a 1D regular π stacking, while the latter forms a 2D π network. Molecular orbital calculations suggest a V(4+)(d(1)) ground state and a characteristic spin polarization on the whole molecular skeleton. The temperature dependence of the paramagnetic susceptibility of the α form clearly indicates a ferromagnetic interaction with a positive Weiss constant of θ = 2.4 K, which is well-explained by McConnells type I mechanism. VOTTDPz forms amorphous thin films with a flat and smooth surface, and their cyclic voltammogram curves indicate a one-electron reduction process, which is highly electrochromic, because of a reduction of the porphyrazine π ring. Thin-film field-effect transistors of VOTTDPz with ionic-liquid gate dielectrics exhibit n-type performance, with a high mobility of μ = 2.8 × 10(-2) cm(2) V(-1) s(-1) and an on/off ratio of 10(4), even though the thin films are amorphous.

Electric double layers allow for opaque electrodes in high performance organic optoelectronic devices

We report that opaque electrodes can be used for high-performance organic optoelectronic devices, facilitated by the electric double layers (EDLs) formed in ionic liquids. For the photocell, gold/poly(3-hexylthiophene-2,5-diyl) (P3HT):[6,6]-phenyl C61 butyric acid methyl ester (PCBM)/ionic liquid/silver, the EDLs enable a large photocurrent response, without the electrodes being superimposed. The external quantum efficiency and responsivity can reach 61.2% and 272 mA/W, respectively. The specific detectivity can reach 1.9 × 1013 Jones, which is larger than silicon-based detectors. This type of architecture will renew the operation principle and material choice for organic photocells, because transparency is no longer an indispensable condition for the electrodes.

Tetrakis(thiadiazole)porphyrazines: 7. Synthesis and structure of μ-oxo-bis[tetrakis(thiadiazole)porphyrazinato-aluminum(III)]

The complex μ-oxo-bis[tetrakis(thiadiazole)porphyrazinato-aluminum(III)], [(TTDPzAl)2O], has been obtained from the corresponding mononuclear Al(III) hydroxo-complex, [TTDPzAlOH], by refluxing a solution of this latter in α-chloronaphthalene or by heating the solid hydroxo species (250–300 °C) under vacuum (10-2 mmHg). The complex, which appears as a stable species in air, shows a typical IR absorption at 983 cm-1, assigned as νas(Al-O-Al). Contact with water determines disappearance of this absorption consequent to the formation of the related hydroxide. [(TTDPzAl)2O], insoluble in most organic non-donor solvents, and very scarcely soluble in dimethylsulfoxide and dimethylformamide, shows some instability in pyridine, with probable breaking of the μ-oxo bridge and formation of the mononuclear hydroxide. Single crystals suitable for X-ray analysis were obtained by subliming [(TTDPzAl)2O] under vacuum at 500 °C under a continuous N2 flow. Crystal data for [(TTDPzAl)2O], C32Al2N32OS8: a = 7.613(2) A, b = 11...

Crystal-to-crystal transformation in solid-state electrochemical doping of Cl− ions to the nanoporous neutral radical lithium phthalocyanine: revelation of electron–electron correlations in the 1D half-filled system

We performed electrochemical doping of Cl− ions to the x-form single crystals of a neutral π radical LiPc, in which the structure consists of 1D stacking chains of LiPc and nanochannels parallel to them. It was found that the LiPc crystals on the working electrode were electrochemically oxidized in an acetonitrile solution of tetrabutylammonium chloride (TBA·Cl), exhibiting a crystal-to-crystal transformation to LiPc·Clx (0 < x < 0.5), in which the x value was controlled by the electrochemical potential. The crystal structures of the LiPc·Clx series were successfully solved and refined by X-ray single-crystal analysis, and the obtained structures clearly indicated the presence of Cl− ions in the 1D channels and a systematic structural change in the π stacking chain of LiPc. As the value of x increased, the interplanar distance between the neighboring LiPc molecules decreased, which was associated with a significant enhancement of conductivity. These oxidative-doping effects indicate that the structural and electrical properties of the 1D half-filled electron system of LiPc are governed by electron–electron correlations between the unpaired electrons.