Yutaka Takaguchi

Facile and reversible synthesis of an acidic water-soluble poly(amidoamine) fullerodendrimer

Water-soluble fullerodendrimer was obtained by the use of a Diels–Alder reaction of C60 with a newly designed anthryl dendron under an extremely mild condition in 70% yield, which is more than five times as high as the yield described in our previous report.

Photosensitized hydrogen evolution from water using a single-walled carbon nanotube/fullerodendron/SiO2 coaxial nanohybrid.

A coaxial nanohybrid consisting of a single-walled carbon nanotube (SWCNT), fullerodendron, and SiO(2) shows high-efficiency light-driven hydrogen evolution from water. Upon visible light irradiation, SWCNT/fullerodendron/SiO(2) coaxial nanohybrid shows hydrogen evolution activity in the presence of methyl viologen (MV(2+)), benzyldihydronicotinamide (BNAH), and a colloidal polyvinyl alcohol(PVA)-Pt.

A photo-responsive hydrogelator having gluconamides at its peripheral branches

A newly designed anthracene derivative having gluconamides at its peripheral branches formed a photo-responsive hydrogel. SEM observation of the xerogel showed a network structure consisting of fibrils. Upon photoirradiation (lambda >300 nm) of the hydrogel, regioselective photodimerization of the anthracene moiety occurred to give head-to-tail photodimers and the physical state changed from the gel to the sol.

Preparation and Electrochemical and Optical Properties of Unsymmetrically Substituted Phthalocyanines with One or Two Trithiole Rings and Related Symmetric Derivatives

4,5-Bis(benzylthio)-3,6-diethylphthalonitrile (1) was mixed with 4 -t-butylphthalonitrile and then treated with lithium alkoxide in n-hexanol to produce the corresponding unsymmetrically substituted phthalocyanines (2) and (3) with two or four benzylthio groups, respectively. Treatment of phthalocyanine (2) with nickel(II) acetate yielded the corresponding metal complex 2-Ni. Two benzyl groups of 2 and 2-Ni were removed with lithium/THF/ammonia at -78 degrees C under argon, and the dithiolate anions generated were then reacted with elemental sulfur to give monotrithiolophthalocyanines (5) and (5-Ni). A similar treatment of 3 produced bistrithiolophthalocyanine (6). Tetrakistrithiolophthalocyanine (7-Ni) was prepared by complexation of phthalocyanine (4) with nickel(II) acetate, followed by a Birch reduction of the resulting nickel(II) complex (4-Ni), and then sulfurization and cyclization of the octathiolate anions that were generated. The structures of the phthalocyanines were determined by (1)H NMR and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The optical and electrochemical properties of the phthalocyanines were examined by UV-vis absorption spectroscopy and cyclic voltammetry. Treatment of 5, 5-Ni, 6, 7, and 7-Ni with trifluoroacetic acid in chloroform generated positively charged species, which were characterized by UV-vis and/or NMR spectroscopy.

Simple, Extremely Fast, and High‐Yielding Oxidation of Thiols to Disulfides

Abstract Results of oxidation of thiols to disulfides with 1,3‐dibromo‐5,5‐dimethylhydantoin (DBDMH) are described. A simple addition of 0.20–0.25 mol equivalent of solid DBDMH to thiol in chloroform at room temperature yielded the disulfides in excellent yield. The reaction is extremely fast and gave no other oxidized side products.

Transport properties of field-effect transistor with Langmuir-Blodgett films of C60 dendrimer and estimation of impurity levels

Field-effect transistor (FET) device has been fabricated with Langmuir-Blodgett films of C60 dendrimer. The device showed n-channel normally off characteristics with the field-effect mobility of 2.7×10−3cm2V−1s−1 at 300K, whose value is twice as high as that (1.4×10−3cm2V−1s−1) for the FET with spin-coated films of C60 dendrimer. This originates from the formation of ordered π-conduction network of C60 moieties. From the temperature dependence of field-effect mobility, a structural phase transition has been observed at around 300K. Furthermore, the density of states for impurity levels was estimated in the Langmuir-Blodgett films.

The Horner–Wadsworth–Emmons reaction of mixed phosphonoacetates and aromatic aldehydes: geometrical selectivity and computational investigation

Abstract The substituent effect on the geometrical selectivity in the Horner–Wadsworth–Emmons (HWE) reaction was studied employing several mixed phosphonoacetates. Their reactions with aromatic aldehydes showed a gradual change in Z -selectivity according to the electron-withdrawing ability of the phosphonate substituents, and there was a good correlation between the observed selectivities and 31 P chemical shifts of the phosphonoacetates. Some variables such as the metal cation and crown ether also affected the selectivity. A computational study using ab initio and semi-empirical calculations suggests that the electron-withdrawing substituents stabilize the intermediates as well as the transition states, which reduces the reversibility to increase Z -products. This is in agreement with the experimentally observed selectivity.

An Extended Phenacene-type Molecule, [8]Phenacene: Synthesis and Transistor Application

A new phenacene-type molecule, [8]phenacene, which is an extended zigzag chain of coplanar fused benzene rings, has been synthesised for use in an organic field-effect transistor (FET). The molecule consists of a phenacene core of eight benzene rings, which has a lengthy π-conjugated system. The structure was verified by elemental analysis, solid-state NMR, X-ray diffraction (XRD) pattern, absorption spectrum and photoelectron yield spectroscopy (PYS). This type of molecule is quite interesting, not only as pure chemistry but also for its potential electronics applications. Here we report the physical properties of [8]phenacene and its FET application. An [8]phenacene thin-film FET fabricated with an SiO2 gate dielectric showed clear p-channel characteristics. The highest μ achieved in an [8]phenacene thin-film FET with an SiO2 gate dielectric is 1.74 cm2 V−1 s−1, demonstrating excellent FET characteristics; the average μ was evaluated as 1.2(3) cm2 V−1 s−1. The μ value in the [8]phenacene electric-double-layer FET reached 16.4 cm2 V−1 s−1, which is the highest reported in EDL FETs based on phenacene-type molecules; the average μ was evaluated as 8(5) cm2 V−1 s−1. The μ values recorded in this study show that [8]phenacene is a promising molecule for transistor applications.

Fabrication of field-effect transistor devices with fullerodendron by solution process

n-channel field-effect transistor (FET) devices have been fabricated with thin films of fullerodendron on SiO2∕Si, polyimide/Au/poly(ethylene terephthalate), and polyvinyl alcohol/Au/poly(ethylene terephthalate) substrates by using solution processes. The value of field-effect mobility μ of the fullerodendron FET reaches 1.7×10−3cm2V−1s−1 at 300K. The mobility gap and optical gap have been estimated to be 0.15 and 1.4eV, respectively. The channel conduction in the FET device follows thermally activated hopping-transport mechanism below 300K.

MOLECULAR DYNAMICS OF STERICALLY HINDERED DIHALO- AND DIACYLOXYDIARYLTELLURANES

Abstract Dihalo- and diacyloxydi(2,6-dimethylphenyl)telluranes [10-Te-C2X2; X = halogen and RCO2] were prepared and variable-temperature 1H NMR studies revealed that these telluranes were composed of the sterically congested rotamers. The first examples of the activation parameters for rotation of the TeC bonds were obtained in D NMR experiments.