Showing papers by "Jean Roncali published in 1996"
TL;DR: In this paper, it was reported that the introduction of electron-with-drawing groups at selected positions of the conjugated chain represents an efficient approach to bandgap con- trol.
Abstract: n-conju- gated systems can contribute to solving several problems posed by their technological applications in electronic and optoelectronic devices16] or nonlinear optics,[71 such as the increase of the number of charge-carriers, tuning of the emission wavelength, and improvement of the electron transmission properties. It has been reported that introduction of electron-with- drawing groups at selected positions of the conjugated chain represents an efficient approach to bandgap con- trol.[14] In this context, the grafting of cyano groups at the ethylene linkage of poly(ary1enevinylenes) has been shown to produce a significant increase of electron-affinity,181 while application of this approach to electrogenerated poly(dithienylethy1enes) has led to a considerable reduc- tion of the bandgap E,.[91
46 citations
TL;DR: In this article, the synthesis of thienylenevinylene oligomers endcapped with 1,3-dithiole-2-ylidene is described, and CV analysis shows that these compounds can be oxidized up to their tetracationic state within a narrow potential window.
18 citations
TL;DR: In this article, the synthesis of a new series of push-push systems based on furan-2,5-diylvinylene oligomers end-capped with l,3-dithiol-2-ylidene electron-releasing groups is described.
Abstract: The synthesis of a new series of push–push systems based on furan-2,5-diylvinylene oligomers end-capped with l,3-dithiol-2-ylidene electron-releasing groups is described. 1H NMR spectroscopy and X-ray diffraction reveal that the molecules adopt a planar conformation stabilized by strong intramolecular interactions. Electronic absorption spectroscopy indicates that the effective conjugation length increases steadily with the length of the π-conjugated system without any evidence of saturation. Analysis of electrochemical behaviour by cyclic voltammetry shows that, whereas all compounds are easily oxidized into stable dications, with extension of the conjugation length the oxidation process progressively evolves from two successive one-electron steps to a single step two-electron transfer.
17 citations
TL;DR: In this paper, the synthesis of new classes of extended hybrid tetrathiafulvalene analogues built around difuryl and dithienyl polyenic π-conjugated spacers containing n = 1, 2, or 3 conjugated double bonds and bearing CO2Me, SMe, and n-propyl substituents (R) at the 1,3-dithiole ring is described.
Abstract: The synthesis of new classes of extended hybrid tetrathiafulvalene analogues built around difuryl and dithienyl polyenic π-conjugated spacers containing n = 1, 2, or 3 conjugated double bonds and bearing CO2Me, SMe, and n-propyl substituents (R) at the 1,3-dithiole ring is described. The electronic absorption spectra of these compounds show that the wavelength of the absorption maximum and the HOMO−LUMO energy gap depend on the nature of the heterocycle, the length of the π-conjugated spacer and the electronic effects of R. Cyclic voltammetry shows that except for n = 1 and R = CO2Me, all compounds are directly oxidized into their dicationic state through a single-step two-electron transfer. The combined effects of the various structural parameters allow oxidation potentials lying among the lowest reported to date for TTF analogues to be reached.
16 citations
11 citations