Chemical Technology May 2016

Fine tuning phosphorous heterocycle materials for organic electronics

of hydrogen fluoride (HF) by the P-arylated 1,3 diphosphacyclobutane-2,4-diyls. This release of HF resulted in remarkable changes in their photoabsorption proper- ties. Analysis showed that 1,3 diphospha- cyclobutane-2,4-diyls absorbed visible light at approximately 600 nm. Futher- more, the researchers fabricated a field effect transistor with a carrier mobility of 1,29 x 10 8 cm 2 / Vs, ON/OFF ratio of 6, and threshold voltage of 4 V. The Tokyo Tech group also found the optical absorption to show a ‘blue shift’ when the open-shell P-heterocyclic system ‘trapped’ hydrogen fluoride (HF); a finding that may enable the visual detection of the existence of HF, and could be used for the development of HF sensors. For more information contact Emiko Kawaguchi at the Centre for Public Affairs and Communications, Tokyo Institute of Technology on

Scientists at the Tokyo Institute of Technol- ogy have produced airstable 1-aryl 1,3-di- phosphacyclobutane-2,4-diyl materials by direct arylation with electron rich aromatic substituents. This method enables the fine tuning of the electronic properties of such phosphorous heterocycles compounds for applications including fabrication of organic electronics and hydrogen fluoride sensors. Materials scientists have a strong inter- est in the development of methods for the synthesis of so-called ‘open-shell singlet P-heterocyclic’ materials systems for appli- cations in the organic electronics industry including organically based sensors and optoelectronic devices. The Tokyo Tech group have previously reported on a nucleophilic aromatic sub- stitution (S N Ar) process for producing air-stable 1-aryl 1,3-diphosphacyclobu- tane-2,4-diyls. However, this method only worked in the case of electron-deficient N-heterocyclic aryl halides were employed as the electrophiles. Hence, there is still the need for new approaches for direct “Fibertex KAVI multiple layer felt liners make it possible to repair even heavily dam- aged pipelines using the ‘no-dig’ method, with numerous advantages over conventional open trench pipe repair procedures,” says Lance Woolley, business development manager, Fib- ertex South Africa. “With these cured-in-place liners, there is no need for excavation during pipeline repair work and thus inconvenience to traffic, production, business or residents is minimised. “These environmentally-friendly, needle- punched, nonwoven felts are designed to restore full or partial pipeline bearing capac- ity, improve hydraulic pipeline parameters, increase flowrate and ensure perfect pipeline tightness. “These felts, which are resistant to abra- sion and chemical agents, are designed to later accept the saturation of epoxy-based polyurethane resins to ensure efficient per- formance and extended service life from the cured pipe liner. Fibertex KAVI needle-punched fabrics also ensure elasticity of the repaired

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arylation of 1,3-diphosphacyclobuten-4-yl anions with electron rich aromatic substitu- ents that produce electron-donating and stable 1,3-diphosphacyclobutane-2,4-diyls for organic electronics. The method developed by the Tokyo Tech group is based on the assumption that, “highly electrophilic arynes should react with and afford stable and electron- donating openshell singlet P-heterocycles.” In their experiments, the researchers gen- erated arynes from the appropriate o-silyl triflates and fluoride, observed them to react with 1,3-diphosphacyclobuten-4-yl anion under appropriate conditions with the result being air-stable open-shell sin- glet P-heterocycles. Notably, during the experiments the researchers also detected the presence

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Chemical Technology • May 2016