Electrochemical oxidation of thin films of s-p-conjugated thienylene-silanylene copolymers, with poly[(hexamethyltrisilanylene) quinque(2,5-thienylene)] (TS5T) as a representative, is investigated in acetonitrile solutions containing different electrolytes. It is found from fluorescence spectroelectrochemical, electrochemical quartz crystal microbalance and FT-IR measurements that Si-Si-Si s-bonding is weakened by electrochemical anion doping in p-conjugated segments of the polymer, resulting in promotion of cleavage of the s-bonding in BF4 and PF6 solutions. Such a doping-enhanced cleavage of the Si-Si-Si bonding is relatively negligible in a ClO4 solution, suggesting some specific interaction between the Si atoms in the polymer chain and the F atoms in BF4 and PF6 anions. In a F solution, on the other hand, the polymer film undergoes electrochemical fluorination and:or chemical dissolution.

UV-visible absorption and fluorescence properties of 14 nano-size star-like compounds, being composed of oligothienylene units bridged by silicon atoms, have been studied in dioxane solution. The absorption and emission maximum wavelengths are found to be dependent on the oligothienylene units. High fluorescence quantum yields and longer lifetimes are observed for the star-like compounds containing bithienylene units, being related to the σ-π interaction and the star-like structure.

Electrochemistry of s-p-conjugated polymers, poly[(hexamethyltrisilanylene)oligo(2,5-thienylene)] has been investigated in acetonitrile by using cyclic voltammetric and spectroelectrochemical techniques. Cyclic voltammograms of these polymers films display generally two pairs of main redox peaks, indicating the doping and dedoping processes of the polymers. The electrochemical oxidation of the polymer films results in their partial decomposition, besides the doping, which is shown by electrochemical quartz crystal microbalance and spectroelectrochemical measurements. The decomposition products are characterized by UV-visible absorption spectroscopy, fluorescence spectroscopy, FT-IR, and GPC measurements. It is concluded that the decomposition originates mainly from electrochemical cleavage of silicon-silicon bonds in the polymer chains, and the electrochemical stability of the s-p-conjugated polymers may be improved by decreasing the oligosilanylene block size in the polymer chains.

UV-visible absorption and fluorescence properties of three series of s-pconjugated polymers (copolymers of alternative oligothienylene and oligosilylene units) have been studied in dioxane solution. The energies of the absorption maximum, fluorescence maximum, and the 0-0 transition are found to be linearly dependent on the reciprocal of the number of thiophene rings in the repeating unit of the polymer chain, but almost independent of the silicon atom number. The s-p-conjugation in the polymers results in red shift in the absorption and fluorescence maxima, higher fluorescence quantum yields, and longer fluorescence lifetimes of the polymers, with respect to their corresponding analogous a-oligothiophenes.

Self-assembled monolayers (SAMs) of two tripod-shaped p-conjugated thiols and a disulfide have been grafted onto Au(111)/mica substrates. These SAMs exhibit oxidation and reduction peaks in the cyclic voltammograms arising from the electrochemical responses of the conjugated oligothiophene parts in the molecules. Organic light-emitting devices have been fabricated by using the SAM-coated Au electrode as the anode. In comparison with the device consisting of Au/TPD/Alq3/Mg-Ag, the electroluminescence performance of the device using the SAM grafted Au electrode is much improved for the SAM of the tripod-shaped thiols and worsened for the SAM of the disulfide. The different influences of the SAMs on the performances are explained by considering structures of the molecules and the SAMs, and the energy level alignment at the related interfaces in the devices.