A series of bithiophene derivatives bearing an intramolecular monosilanylene or disilanylene bridge between the β,β‘-positions were synthesized, and their properties were investigated. UV spectral and cyclic voltammetric analyses of the silicon-bridged bithiophenes indicated that they have lower lying LUMOs, relative to those for bithiophene and methylene bridged bithiophenes, probably due to σ*−π* interaction between the silicon atom(s) and bithiophene π-orbitals, in good agreement with the results of theoretical calculations using simplified model compounds based on RHF/6-31G. The silicon-bridged bithiophenes exhibit high electron-transporting properties, and triple-layer-type electroluminescent (EL) devices, using the silicon-bridged bithiophenes, tris(8-quinolinolato)aluminum(III) complex (Alq), and N,N‘-diphenyl-N,N‘-di-m-tolylbiphenyl-4,4‘-diamine (TPD) as the electron-transporting, emitting, and hole-transporting layers, respectively, emitted strong EL.

Dithienosiloles (DTSs) bearing conjugated aryl substituents on the thiophene rings (1 and 2) were prepared and their optical, electrochemical, and electron-transporting properties were investigated in comparison with those of simple DTSs having no conjugated substituents on the thiophene rings (4-6). UV absorption bands of 1 and 2 are red shifted from those of 4-6 by 40-80 nm, reflecting the expanded π-conjugation, whereas the first oxidation peaks in the cyclic voltammograms of 1 and 2 appear at potentials a little lower or almost the same energies relative to those of 4-6, depending on the nature of the substituents. The electron-transporting properties of 1 and 2 were evaluated by the performance of electroluminescent (EL) devices having vapor-deposited DTS, Alq, and TPD layers, as the electrontransport, emitter, and hole-transport, respectively. The results indicated that introduction of aryl substituents to DTSs led to inferior performance of the devices in most cases, while the device with 1c bearing trimethylsilylpyridyl substituents exhibited high efficiency of current-luminance energy conversion and emitted a green light with a maximum luminance of 16 000 cd/m 2 . A trap-controlled electron transporting model is proposed to explain their performance. OM0103254 (14)

Nine new kinds of thermosetting polymers with the Si(H)OC'C unit were synthesized by dehydrogenative polycondensation reactions between hydrosilanes and diethynyl compounds in the presence of a magnesia catalyst. Phenylsilane, silane, vinylsilane, and n-octylsilane were used as the hydrosilanes, and 1,3-diethynylbenzene, 1,4-diethynylbenzene, 4,4Ј-diethynyldiphenyl ether, and 1,3-diethynyl-1,1,3,3-tetramethyldisiloxane were used as the diethynyl compounds. All the polymers were thermosetting, highly heat-resistant, easily soluble in a solvent, and moldable. In particular, OSi(R)HOC'COC 6 H 4 OC'CO (R ϭ H or CHACH 2 ) showed high thermal stability; the temperature of 5% weight loss was greater than 800°C, and the residue at 1000°C was over 90%. The thermal stabilities of the polymers were attributed to the crosslinking reaction of the SiOH and C'C bonds.