Joji Ohshita

Dye‐Sensitized Solar Cells Based on Donor‐π‐Acceptor Fluorescent Dyes with a Pyridine Ring as an Electron‐Withdrawing‐Injecting Anchoring Group

A new-type of donor-acceptor π-conjugated (D-π-A) fluorescent dyes NI3-NI8 with a pyridine ring as electron-withdrawing-injecting anchoring group have been developed and their photovoltaic performances in dye-sensitized solar cells (DSSCs) are investigated. The short-circuit photocurrent densities and solar energy-to-electricity conversion yields of DSSCs based on NI3-NI8 are greater than those for the conventional D-π-A dye sensitizers NI1 and NI2 with a carboxyl group as the electron-withdrawing anchoring group. The IR spectra of NI3-NI8 adsorbed on TiO(2) indicate the formation of coordinate bonds between the pyridine ring of dyes NI3-NI8 and the Lewis acid sites (exposed Ti(n+) cations) of the TiO(2) surface. This work demonstrates that the pyridine rings of D-π-A dye sensitizers that form a coordinate bond with the Lewis acid site of a TiO(2) surface are promising candidates as not only electron-withdrawing anchoring group but also electron-injecting group, rather than the carboxyl groups of the conventional D-π-A dye sensitizers that form an ester linkage with the Brønsted acid sites of the TiO(2) surface.

Base-free oxidative homocoupling of arylboronic esters

Abstract Base-free oxidative homocoupling reaction of arylboronic esters has been found to proceed using a catalytic amount of a palladium–1,3-bis(diphenylphosphino)propane (DPPP) complex under an oxygen atmosphere, affording a variety of biaryls in modest to excellent yields. Even arylboronic esters bearing a base-sensitive functional group are applicable to the reaction.

Dye-sensitized solar cells based on D-π-A fluorescent dyes with two pyridyl groups as an electron-withdrawing-injecting anchoring group.

D-π-A fluorescent dye with two pyridyl groups as an electron-withdrawing-injecting anchoring group possessing a high coordinate bonding ability to Lewis acid sites on the TiO2 surface, which can lead to high dye loading on the TiO2 film and efficient electron injection, has been developed as a new type of D-π-A dye sensitizer for dye-sensitized solar cells.

Three‐Component Coupling of Arynes and Organic Bromides

Arynes have been versatile tools in synthetic organic chemistry for the facile construction of benzoannulated structures and multisubstituted arenes. Despite the labile and transient character arising from the highly strained C C bonds, the use of a suitable combination of nucleophiles and electrophiles allows arynes to serve as connectors between these two components, thus leading to various three-component coupling reactions of high synthetic significance; in the reaction zwitterions (1,n-dipoles) generated from the arynes and nucleophiles act as key intermediates. 3] In view of the fact that almost all three-component coupling reactions reported so far employ classic electrophiles (e.g., carbonyl compounds, sulfonylimines, and CO2) as the third component, [4] there should be a number of unexploited three-component coupling reactions with potential synthetic utility that would be made feasible by employing a new type of third component. We report herein that 1,3or 1,4-dipoles generated in situ from arynes can be captured by alkynyl (or polyfluoroaryl) bromides, which serve as a source of bromine cations and alkynyl (or polyfluoroaryl) anions, thus leading to the direct construction of functionalized bromoarenes having diverse structures. We first conducted the reaction of benzyne (from 1a and KF/[18]crown-6), 1,1,3,3-tetramethylbutyl isocyanide (tOctNC; 2a), and phenylethynyl bromide (3a) in DME at 0 8C, and observed that two C C bonds and a C Br bond formed all in one pot to give the three-component coupling product 4a in 88% yield (Scheme 1). As described in Scheme 2, the reaction would be triggered by formation of the zwitterion (1,3-dipole) 5 from benzyne and 2a. Subsequent nucleophilic attack of the aryl anionic moiety on the bromo moiety of 3 a produces the phenylacetylide 7 and an aryl–Br bond in 8 through the bromine ate complex 6, with subsequent C C bond formation between 7 and the nitrilium cation 8 to furnish 4a. Products derived from various alkynyl bromides bearing a substituted aryl (4b–4d), thienyl (4e), or enynyl (4 f) moieties were obtained. The doubly coupled product 4g was produced from 1,4-bis(bromoethynyl)benzene in 66% yield (Scheme 1). The reaction was also applicable to aliphatic alkynyl bromides whose acetal or propargylic ether moiety remained intact (4h–4j), and moreover, the functionalized iodoarene 4 k could be synthesized by use of phenylethynyl iodide. Next, we examined the threecomponent coupling with substituted arynes. The respective products from dimethylbenzynes (4 l and 4m) and cyclo-

Photovoltaic performance of dye-sensitized solar cells based on D–π–A type BODIPY dye with two pyridyl groups

D–π–A type boron dipyrromethene (BODIPY) dye YH-1, which has two pyridyl groups as electron-withdrawing-anchoring groups at the end of the 3- and 5-positions and a carbazole-diphenylamine moiety as an electron donor at the 8-position on the BODIPY core, was designed and developed as a photosensitizer for dye-sensitized solar cells (DSSCs). It was found that the dye YH-1 possesses a good light-harvesting efficiency (LHE) in the red/near-IR (NIR) region and good adsorption ability on TiO2 film. We demonstrate that the expansion of the π-conjugated system by the introduction of not only the carbazole-diphenylamine moiety and the thiophene unit at the 8-position but also two thienylpyridines at the 3- and 5-positions on the BODIPY core can lead to red-shift and broadening of the absorption band in the red/NIR region. DSSCs based on YH-1 exhibit incident photon-to-current conversion efficiency of ca. 10% over a range of 500 to 700 nm, with an onset at 800 nm.

Direct access to anthranilic acid derivatives via CO2 incorporation reaction using arynes.

CO2 was found to be directly convertible into anthranilic acid derivatives of great synthetic value through a three-component coupling using arynes and amines. Zwitterions arising from nucleophilic attack of amines to arynes serve as key intermediates in the coupling.

Synthesis and properties of dithienosiloles

Abstract A series of dithienosilole derivatives were synthesized and some of their properties were investigated. UV spectra of dithienosiloles show absorption bands around 350 nm and their cyclic voltammograms display oxidation peaks at about 1.2 V vs. SCE. Nickel-catalyzed coupling of 2,6-dibromodithienosilole with the diGrignard reagent prepared from bis(5-bromothienyl)tetraethyldisilane afforded an alternating polymer composed of a 2,6-dithienyldithienosilole system and tetraethyldisilanylene unit. When the polymer film was doped with FeCl3 vapor, the film became conducting with the maximum conductivity of 7.0×10−3 S/cm.

Doping-induced change of carrier mobilities in poly(3-hexylthiophene) films with different stacking structures

Abstract Mobilities of positive charge carriers in poly(3-hexylthiophene) (PHT) films of 54%, 70%, 81%, and 97% in regioregularity were electrochemically measured over a range of doping levels. The results show that better ordered stacking structures enhance mobilities, but affect little features of the mobility change by doping. The common doping level of ca. 1% for the onset of the drastic mobility increase implies that the π–π stacking structures facilitating a charge transport in neutral or lightly doped PHT films are not responsible for the evolution of metallic conduction in PHT films.

Platinum-catalysed diborylation of arynes: synthesis and reaction of 1,2-diborylarenes.

Arynes are found to be facilely inserted into bis(pinacolato)diboron by using a platinum-isocyanide catalyst, affording diverse 1,2-diborylarenes, which can be converted into o-terphenyls via Suzuki-Miyaura coupling reaction.

Straightforward construction of diarylmethane skeletons via aryne insertion into carbon–carbon σ-bonds

Two molar amounts of arynes were found to couple with nitriles via carbon-carbon sigma-bond cleavage, assembling diverse diarylmethane skeletons in a straightforward manner.