Synthesis And Properties Of Radical Compounds Based On Tetrathiafulvalene And Its Derivatives

Tetrathiafulvalene (TTF) has been intensively studied due to its unique π-electron donor and redox properties. TTF and its derivatives have been used as versatile building blocks in supramolecular and material chemistry. The cyclic voltammetry shows that TTF can be oxidized to the radical cation and dication under proper potential. However, the two step-by-step oxidizations are reversible, and both the radical cation and dication are short-life compounds for the sensitivity to oxygen and moisture. So the key problem in preparing the radical cation and dication of TTF lies in how to stabilize these short-life compounds.In this dissertation, in order to stabilize radical compounds of TTF and its derivatives, we use specific silver-salt oxidants involving weakly coordination anions and succeed in producing radical compounds based on three kinds of TTF derivatives under strict moisture-free and oxygen-free conditions. All the compounds are well-soluble in some solvents and have been systematically investigated by X-ray single crystal diffraction, element analysis, UV-Vis absorption spectra,’H-NMR, electron para-magnetic resonance (EPR) and magnetism measurements.1.The Radical Cation and Dication of Tetrakis-(methylthio)tetrathiafulvalene Stabilized by a Weakly Coordinating AnionAfter the chemical oxidation of the neutral tetrakis-(methylthio)tetrathiafulvalene by specific oxidation agents with weakly coordinating anion, [Al(ORF)4]-[ORF =OC(CF3)3],the radical cation TMT-TTF’+ and dication TMT-TTF2+ were successfully stabilized and isolated. All the compounds are well-soluble in some solvents and have been systematically investigated by absorption spectra,1H-NMR, electron para-magnetic resonance (EPR) measurements. Their crystal structures and electronic properties have been studied in conjunction with theoretical calculation. The synthetic approach for chemical oxidation by specific salts of weakly coordinating anions is very useful for stabilizing radical cations of tetrathiafulvalene (TTF) and its derivatives in both solution and solid state, which will extend the further research, including the structure-property relations on stable radicals for TTF derivatives and new functional materials based on them.2. Synthesis and Oxidization of Phenyl Modified TetrathiafulvaleneA new TTF derivative bis(phenylenedithio)tetrathiafulvalene (BPhDT-TTF,5) modified by benzene has been synthesized and characterized, which is hardly soluble in common solvents. The chemical oxidization using two oxidation agents including bulky and weakly coordinating anions, [Al(ORF)4]- and [B(C6F5)4]-, resulted in the formation of three stabilized and well-soluble radical cation salts, namely [5·+][Al(ORF)4] (6), [Ag(5·+)]n[Al(ORF)4]2n (7), and [5·+][B(C6F5)4] (8). Among them, 6 and 8 are typical 1:1 radical cations. The complex 7 is a rare 1-D chain formed by the radical cations 5·+ coordinating to silver (I) ions. Importantly, upon oxidization, all three radical compounds (including the polymeric metal complex 7) made from the slightly soluble TTF precursor become soluble in common organic solvents. Thus, all these compounds are able to be systematically investigated by absorption spectra, EPR and magnetic measurements. Their crystal structures and electronic properties have been studied in conjunction with theoretical calculation.3. Synthesis and Oxidization of Long-chain Tetrathiafulvalene with Multi-sulfurA series of well-soluble long-chain TTFs with multi-sulfur have been synthesized after the introducing of substituent group containing tert-butyl, including compound 12 (TTF-Ph-(SR)4) with twelve sulfurs and compound 15 with sixteen sulfurs. After the chemical oxidation by Ag[Al(ORF)4], the radical cation of 12 has been made and the single crystal suitable for X-ray crystallographic studies was obtained by evaporation in CH2Cl2-CH3CN(1:1 v/v) in air atmosphere under room temperature. The X-ray single crystal diffraction, element analysis, UV-Vis absorption spectra,1H-NMR and electron para-magnetic resonance (EPR) adequately conformed that TTF-Ph-(SR)4 has been oxidized to its radical cation compound.