Large TTF With 12 Sulfur Atoms For Molecular Conductor

In the several decades development history of the molecular conductors, more than 120 superconductors have been synthesized. Great achievements have been made in the field of molecular conductors. The TTF (tetrathiafulvalene) and its derivatives present the most excellent conductive property in all molecular conductors.The main goal of this thesis is the closed-loop large TTF-based molecular conductors with 12 sulfur atoms. We introduce their syntheses, structures and electronic properties.1. The symmetrical molecular conductor BEDT-TTP (2,5-bis[4,5-(ethylenedithio)--1,3-dithiol-2-ylidene]-1,3,4,6-tetrathiapentalene) has been synthesized and its crystal structure at 295 K has been determined. It crystallizes in the space group C2/c. The structure precision parameters are:R1=0.0516,△p=0.55,-0.35 e/A3 when the completeness is 96%(20=54°). There is not A and B level alert in the checkCIF report of International Union of Crystallgraphy. Meanwhile, the crystal structure of EODT-TTP has been determined.Figure 1 The molecular structure of BEDT-TTP (295 K)Figure 2 The molecular structure of EODT-TTP (220 K) 2. A new phase of the symmetrical molecular conductor BVDT-TTP (2,5-bis[4,5-(vinylenedithio)-1,3-dithiol-2-ylidene]-1,3,4,6-tetrathiapentalene) has been determined. The crystal belongs to the P21 space group. All the hydrogen atoms have been found in the Fourier map.The structure precision parameters are:R1=0.0350,△p=0.54,-0.28 e/(?)3 when the completeness is 99%(2θ=55°). There is not A and B level alert in the checkCIF report of International Union of Crystallgraphy.Figure 3 The molecular structure of BVDT-TTP (130 K)3. The unsymmetrical molecular conductor EVDT-TTP (2-[4,5-(ethylenedithio)-1,3-dithiol-2-ylidene]-5-[4,5-(vinylenedithio)-1,3-dithiol-2-ylide ne]-1,3,4,6-tetrathiapentalene) has been synthesized and its crystal structure at 294 K and 120 K has been determined. The crystal belongs to the P21/c space group. One molecule is planar and the other is ski type in the cell.Figure 4 The molecular structure of EVDT-TTP (P21/c space group,120 K) The structure precision parameters are:R1=0.0377, Ap=0.85,-0.44 e/(?)3 when the completeness is 98%(2θ=56°) at 120 K. There is not A level alert in the checkCIF report.4. The unsymmetrical molecular conductor EMDT-TTP (2-[4,5-(ethylenedithio)-1,3-dithiol-2-ylidene]-5-[4,5-(methylenedithio)-1,3-dithiol-2-yli dene]-1,3,4,6-tetrathiapentalene) has been synthesized and its crystal structure at 150 K has been determined. The crystal belongs to the P-1 space group.The structure precision parameters are:R1=0.059,△p=0.92,-0.57 e/(?)3 when the completeness is 94%(2θ=55°). There is not A level alert in the checkCIF report.Figure 5 The molecular structure of EMDT-TTP (150 K)5. The conductivities of four large TTF-based molecular conductors have been determined. The conductivities are in the 1×10-5～5×10-3 S/cm as single-component molecular conductors. So far, the synthetic single-component molecular conductors which have good conductivities are very few. Furthermore, the four crystals were exposed to iodine vapor. We found that iodine doping can improve the conductivities of the crystals. The sequence of resistivity is BVDT-TTP (1×105)> BEDT-TTP (1×103)> EVDT-TTP (4×102)> EMDT-TTP (2×102). The result is consistent with the calculated LUMO-HOMO energy-band Eg (eV) which is BVDT-TTP (3.497)> BEDT-TTP (3.491)> EVDT-TTP (3.483)> EMDT-TTP (3.462).There exists certain width between LUMO and HOMO bands because of the strong molecular interactions. The band gap of LUMO-HOMO band should be 1eV. 6. The charge transfer properties of the large TTF-based electron donors with 12 sulfur atoms and middle TTF-based electron donors with 8 sulfur atoms have been determined by cyclic voltammogram. The sequence of the first equilibrium potential about four large TTF-based electron donors is BVDT-TTP (0.68)> EVDT-TTP (0.66)> EMDT-TTP (0.63)> BEDT-TTP (0.58). This is consistent with the first ionization by theoretical calculation which is BVDT-TTP (6.17)> EVDT-TTP (6.07)> EMDT-TTP (6.05)> BEDT-TTP (5.99).These bring us some inspiration from the perspective of material design. (Ⅰ) The donating electron capacity of large TTF-based electron donors is easier than the middle TTF-based electron donors. (Ⅱ) For the similar electron donor with the same sulfur atoms numbers, the donating electron capacity of donor which its two ends are single bonds is better than double bonds.Figure 6 The CV curve of BEDT-TTP in the PhCN/CS27. We found the second and the first ionization energy difference AE can reflect theπconjugation of molecule. Theπconjugation became better with the smaller AE.8. We calculated the configuration of large TTF-based electron donors by the density functional theory (DFT). The results shows the free molecule stable configurations are the S-bend. We found that the molecules can became flat with the loss of electron. When the molecule loses two electrons, the molecule is basically flat except the end alkyl. Figure 7 The configuration of EMDT-TTP9. The molecular conductor ofθ-(BEDT-TTF)2(H3O)(CH3PhSO3)2(H2O)5 has been synthesized by the electrocrystallization method and the H3O+ has been determined accurately. The positive charge of the BEDT-TTF cation is+0.5.10. The conductive complex {[Mn(C5O5)(2,2-bipy)(H2O)].H2O}n shows an one-dimensional coordination chain. The conductivity is 2.5x10-7 S/cm and shows semiconductor behavior in the room temperature.Figure 8 The one-dimensional coordination chain of{[Mn(C5O5)(2,2-bipy)(H2O)].H2O}n...