Asymmetric Synthesis And Electrochemical Properties Of Ttf Derivatives

Tetrathiafulvalene (TTF) and its derivatives have been studied for more than 30 years as π-electron donors. In particular, discoveries of superconductivity in the cation radical salts based on first TMTSF and subsequently BEDT-TTF have stimulated considerable attention for the development of new π-electron donors. Recently, more and more work has been carried out to study n conjugatec system including TTF. For these system, one of the research direction was to reduce coulomb repulsion through extending n conjugated and make donors easier polarized, increase the number of sulfur so that to enhance intermolecular effect.In this thesis, three asymmetric extended π-election systems tetrathiafulvalene deri -vatives, 2,3-vinylenedithio-5,6-didodecylthio tetrathiafulvalene, 2,3-vinylenedithio-5,6 -dihexdecylthio tetrathiafulvalene and 2,3-vinylenedi.hio-6,7-dicyanoethylthio tetrathia -fulvalene, have been synthesized. The molecular structure was identified and characterized by IR, MS, 1H-NMR and elementary ana ysis.Cyclic voltammetry expertiments of synthetical etrathiafulvalene derivatives have been carried out. These compounds exhibit two couple of oxidation waves, but it is not strict electrochemically reversible process. With the increase of the length and number of alkyl chains,the oxidation potentials are turned to small and electron-donating ability is enhanced. The E1/2 value of 2,3-vinylenedithio-5,6 -dihexdecylthio tetrathiafulvalene is the lowest in these TTF derivatives studied here, suggesting the smallest coulombic repulsion.To shed futher light upon the connect of the stucture and the electrochemical propertyes of alkylidenethio tetrathiafulvalene derivatives we synthesized, theoretical calculations were performed. The electron cloud on the highest occupied frontier orbits(HOMO) of system neutral molecules concen:rated at TTF fragment, therefore these fragment is the oxidation center, accorda lting with the electron transfer mechanism that we forecasted. In oxidation, the energy of the HOMO of the radicalcation is -9.12 eV. EHomo between the energy of the TOMO orbital of the radical cation in its optimized form and in the comformation of the neutral species is 3.67 eV. This value was less than the result of 2,3-ethylenedithio-5,6-dialkylidenethio tetrathia -fulvalene (Uhomo=4.07 eV) at the same level compution, meaning that its the second electron removal was easier than 2,3-ethylenedithio-5,6-dialkylidenethio tetrathiaful -valene.The geometric structure of 2,3-vinylenedithio-6,7-dicyanoethylthio tetrathiaful -valene was optimized by the method B3P86/6-31G(d) of quantum chemistry. On the basis of the results, we work out its electronic spectroscopic properties. It is accordant with the experimental value. Electron transitions were discussed.