Organic semiconductors based on small molecules with thermally or photochemically removable groups

Solution processable organic semiconducting small molecules are desirable for the manufacture of low-cost, large-area electronic products on flexible substrates. This article provides an overview of recent progress in OFETs based on solution processable small molecules that can be converted to insoluble organic semiconducting materials on films by thermal or photochemical removal of leaving groups after fabrication of the film.     

π-Fused bis-BODIPY as a candidate for NIR dyes

Benzene-fused bis-(borondipyrromethene)s (bis-BODIPYs) were synthesized by retro-Diels-Alder reaction of the corresponding bicyclo[2.2.2]octadiene-fused (BCOD-fused) bis-BODIPYs, which were, in turn, prepared from 4,8-ethano-4,8-dihydropyrrolo[3,4-f]isoindole derivatives. The π-fused bis-BODIPY chromophores were designed to show intensive absorption and strong fluorescence in the near-infrared region and not to have any strong absorption in the visible region. A 6,10-dibora-5a,6a,9a,10a-tetraaza-s-indaceno[2,3-b:6,5-b']difluorene derivative (syn-bis-benzoBODIPY) obtained by a thermal retro-Diels-Alder reaction of the corresponding BCOD-fused BODIPY dimer has strong absorption and emission bands at 775 and 781 nm, respectively. The absolute quantum yield is 0.36. The absorption is more than 5.0 times stronger than other absorptions observed in the visible region. In the case of 6,15-dibora-5a,6a,14a,15a-tetraaza-s-indaceno[2,3-b:6,7-b']difluorene derivatives (anti-bis-benzoBODIPY), the absorption and emission maxima exceed 840 nm.     

Liposome solubilization induced by surfactant molecules in a microchip

The dynamics of liposome solubilization was monitored by dynamic light scattering and optical microscopy. A newly designed Y-shape microchannel connected to a room was incorporated into a microchip and the reaction processes of the liposome suspension and surfactant solution were observed in the room after mixing the two fluids and stopping the flow. By using this microchip, we succeeded in real-time monitoring of liposome solubilization and the following dynamic processes of solubilization were proposed: 1) Deformed liposomes become spherical. 2) The liposome size increases until the surfactant/liposome ratio in the liposome membrane reaches a threshold value. 3) Mixed micelles of surfactants and phospholipids are released and the liposomes collapse.     

Catalytic Electrochemical C-H Iodination and One-Pot Arylation by ON/OFF Switching of Electric Current

Palladium-catalyzed electrochemical iodination and one-pot arylation of arylpyridines are described. Ortho-selective C-H iodination proceeded via dual activation of each substrate by a palladium catalyst and an electrode. Various aryl groups were introduced at the ortho positions of arylpyridines by ON/OFF switching of two different catalytic cycles using the same palladium catalyst in a one-pot fashion.     

Spectroscopic and magnetic properties of the metastable states in the coordination network [{Co(prm)2}2{Co(H2O)2}{W(CN)8}2]·4H2O (prm = pyrimidine)

The study of the metastable states, obtained by thermal quenching or by light irradiation in the [{Co(prm)(2)}(2){Co(H(2)O)(2)}{W(CN)(8)}(2)]·4H(2)O complex, is reported using powder X-ray diffraction, Raman spectroscopy, optical reflectivity, and magnetic measurements. This compound is characterized by a electron-transfer (ET) phase transition occurring between a high-temperature phase (HT phase) formed by paramagnetic Co(II)-W(V) units and a low-temperature phase (LT phase) formed by diamagnetic Co(III)-W(IV) units. Metastable phases can be induced at low temperature either by thermal quenching rapidly cooling phase named RC or by irradiation photo-induced phase named PI similar to the well-known Light-Induced Excited Spin State Trapping effect. The relaxation dynamics of the metastable phases have been studied and revealed some differences between the RC and PI phases. The sigmoidal shape of the relaxation curves in the RC phase is in agreement with the cooperative nature of the process. Thermodynamic parameters that govern the relaxation have been determined and used to reproduce the experimental Thermal-Induced Excited Spin State Trapping curve.     

The comparison of two clean-up procedures, multifunctional column and immunoaffinity column, for HPLC determination of ochratoxin A in cereals, raisins and green coffee beans

To evaluate a clean-up method of detecting ochratoxin A (OTA) by HPLC, the performances of two different clean-up columns, an immunoaffinity column and a multifuntional column were compared in an inter-laboratory study. As samples, un-contaminated wheat, corn grits, green coffee beans and naturally contaminated raisins were used. The recovery test was performed at two different concentrations of OTA (0.5 and 5.0 μg/kg) except for naturally contaminated raisins. Using the immunoaffinity column, the recovery rates, and relative standard deviations for repeatability (R.S.D._r) and reproducibility (R.S.D._R) for wheat, corn grits and green coffee beans ranged 59.0-85.8, 4.2-7.8 and 22.9-29.2%, respectively. For naturally contaminated raisins, recovery, R.S.D._r and R.S.D._R were 84.1, 1.8 and 5.1%, respectively. Using the multifunctional column, the recovery rates, R.S.D._r and R.S.D._R for wheat, corn grits and green coffee beans ranged 80.8-185.0, 0.7-6.9 and 15.2-33.9%, respectively. For naturally contaminated raisins, the recovery, R.S.D._r and R.S.D._R were 128.7, 1.1 and 3.7%, respectively. The results suggest that a multifunctional column could be used to detect OTA in wheat and corn grits at a concentration as low as 0.5 μg/kg; however, it was difficult to detect OTA in green coffee beans and raisins at such a low level. Although an immunoaffinity column could be used for all the test samples in this study from a low level to a high level, the recovery rates were lower than with a multifunctional column.     

Versatile synthetic method for sphingolipids and functionalized sphingosine derivatives via olefin cross metathesis

A highly efficient and versatile method for the synthesis of various sphingolipids, such as sphingomyelin, ceramide, sphingosine, sphingosine 1-phosphate, and functionalized sphingosine derivatives, was established by two types of combinations of the olefin cross metathesis reaction. One reaction was between the same olefin part and appropriate amino alcohols, which were prepared starting from N-Boc-L-serine, and the other was between appropriate olefins and the same amino alcohol. [reaction: see text].     

A metallic (EDT-DSDTFVSDS)2.FeBr4 salt: antiferromagnetic ordering of d spins of FeBr4- ions and anomalous magnetoresistance due to preferential pi-d interaction

The 2:1 salt of a new donor molecule, EDT-DSDTFVSDS with FeBr4- ion, (EDT-DSDTFVSDS)2.FeBr4 showed an essentially metallic behavior despite a small upturn in the electrical resistance below ca. 30 K (electrical conductivities at 290 and 4.2 K are 200 and 170 S cm-1, respectively). The Fe(III) d spins of the FeBr4- ions in this salt were subject to antiferromagnetic ordering at 3.3 K by virtue of a strong pi-d interaction (Jpid) which is comparable to that in a molecular metallic conductor, lambda-(BETS)2.FeCl4, and of a very weak d-d interaction (Jdd). This strong pi-d interaction was evidenced by a large and negative magnetoresistance effect (ca. 20% at 5 T) as well as by the appearance of a large dip in the resistance at the magnetic field (ca. 2.0 T) parallel to the easy axis for the spin-flop transition of the Fe(III) d spins.     

Three new lignans, longipedunins A-C, from Kadsura longipedunculata and their inhibitory activity against HIV-1 protease

Three new lignans, longipedunins A (1), B (2) and C (3), together with three known compounds, benzoyl-binankadsurin A (4), acetyl-binankadsurin A (5) and schisanlactone A (6), were isolated from Kadsura longipedunculata. Their structures and stereochemistry were determined by spectral and single-crystal X-ray analyses. Compounds 1 and 6 showed appreciable inhibitory activity against HIV-1 protease with IC50 values of 50 and 20 microM, respectively.