RESUMO
Quaterthiophenes 4T, Oct-4T, and Tol-4T based on a central 2,2'-bithiophene core alpha,omega-terminated with 4,4-unsubstituted and 4,4-disubstituted n-octyl or p-tolyl indeno[1,2-b]thiophene have been synthesized by Stille or Miyaura-Suzuki couplings. Compound 4T was also synthesized by an alternative route involving a soluble precursor bearing solubilizing trimethylsilyl groups which have been eliminated in the last step. The electronic properties of the compounds have been analyzed by cyclic voltammetry, UV-vis absorption and fluorescence emission spectroscopy. Thermal evaporation of 4T and Oct-4T leads to crystalline thin films and UV-vis absorption and X-ray diffraction data for these films suggest that the molecules adopt a quasi-vertical orientation onto the substrate. Strong pi-pi intermolecular interactions have been observed for 4T but not for molecules Oct-4T due to the presence of n-octyl chains. Sublimed thin films of Tol-4T show an amorphous character. The characterization of field-effect transistors fabricated from these three materials gave a hole-mobility of 2.2 x 10(-2) cm2 V(-1) s(-1) with an on/off ratio of 2.2 x 10(4) for 4T while no field-effect was observed for Oct-4T and Tol-4T.
RESUMO
The synthesis and resolution of electronically varied axially chiral Quinazolinaps is reported. These ligands bear different aryl groups on the donor phosphorus atom and were synthesised as part of our investigations into electronic effects within this ligand class. A diastereomerically pure palladacycle of one ligand was characterised by X-ray crystallography. The application of these Quinazolinaps to the rhodium-catalysed hydroboration of vinylarenes resulted in enantioselectivities of up to 92%. Their application to the palladium-catalysed allylic alkylation of 1,3-diphenylprop-2-enyl acetate resulted in conversions of up to 99% and enantioselectivities of up to 94%.