多臂TTF类电子给体的合成及物性研究

【作者】 邹雷；

【导师】 朱道本；

【作者基本信息】 复旦大学 ， 有机化学， 2003， 博士

【摘要】 有机导体、有机超导体是从70年代开始兴起的研究领域，它涉及有机化学、物理化学、电子学等学科，属新型交叉研究领域。自1973年第一个有机导体TTF-TCNQ（TTF＝四硫富瓦烯，TCNQ＝7,7,8,8-四氰基对亚甲基苯醌）发现以来，人们为了得到具有电导和超导特性的阳离子盐, 以TTF为结构单元合成了数以百计的衍生物。其中以TTF为基础得到的超导体BEDT-TTF盐，其Tc > 10K。目前临界温度最高的有机超导体Tc可达11-13K（不包括C60体系）。迄今为止，大多数有机导体是准一维导体，低温时存在Peierls-Frohlich相变，由金属态转变为绝缘体。随着研究的不断深入，人们发现提高分子间的相互作用，增加维数可以抑制这种金属态的失稳性，从而使获得超导体成为可能。考虑到在给体分子中引入多个TTF单元可以通过增加分子间的S-S相互作用来增加维数，且对研究多电子氧化还原的分子开关及分子磁体也很有意义，所以我们设计并合成了含有多个TTF单元的多臂给体，并对它们进行了电荷转移复合物和导电LB膜的研究，获得了如下结果：1. 合成了五个含2~4个TTF单元的新型电子给体1-3b，并经1H NMR, FT-IR, 高分辨质谱确定了它们的结构。<WP=6>2. 对所合成的给体1-3a,b进行了电化学研究，采用循环伏安法测得了它们在CH2Cl2中的氧化-还原电位。我们发现它们具有与ET类似的给电子能力，（E11/2 ≈ 0.46-0.51V，E21/2 ≈ 0.84-0.89V vs SCE），说明TTF单元间无明显的相互作用。3. 对2a和3a进行了导电LB膜的研究，对二种LB膜分别进行了AFM, 紫外－可见光谱，红外光谱及电性能测量，发现与溶液中的分子相比，膜的紫外吸收发生了红移（(max从390 nm迁移至410 nm左右），而掺I2前后的红外光谱也都发生了明显变化。电性能测量结果表明，2a掺I2后膜的电导率优于掺I2前,从2.7×10-7 Scm-1提高到1.4×10-5 Scm-1，而3a的膜掺I2前后无显著变化，仍处于同一个数量级：掺I2前为6.25×10-6 Scm-1, 掺I2后为7.57×10-6 Scm-1。4. 对所合成的给体分子4（双-（亚乙基二硫基-四硫富瓦烯硫）-乙烷进行了自身单晶的培养，并通过化学扩散法、电化学氧化法分别得到了给体分子4与TCNQF4形成的电荷转移复合物单晶及与对阴离子PF6-, AsF6-, BF4-形成的阳离子自由基盐的单晶, 对它们用红外光谱、元素分析进行了表征；经X-衍射测定了它们的结构，对其中的分子构型和排列方式进行了比较研究；采用四探针方法对它们的电性能进行了测试，其中4?(TCNQF4)2的电导率σrt < 10-7 Scm-1，所以为绝缘体。其它三个阳离子自由基盐从室温到100K范围内均呈现为半导体特性。更多还原

【Abstract】 Since the first organic metal TTF-TCNQ was discovered in 1973, great progress has been achieved in the field of organic conductors and superconductors. Efforts are still been devoted to improving the interesting conductive properties of the charge-transfer salts or cation-radical salts by increasing the dimensionality of these materials which can suppress the Peierls-Frohlich distortion at low temperature. One of the most interesting approaches employed for increasing dimensionality is enhancing the intermolecular interactions in the cation radical salts by means of chemical modification of TTF molecule, which is essential for the realization of highly conducting metallic and supercondcuting organic charge transfer salts. Here, we would like to report the synthesis and electrochemical properties of one TTF dimmer(1) and two novel TTF trimers(2a,b) as well as two TTF tetramers(3a,b). The studies of their cation-radical salts ( and charge-transfer salts ) and conductive LB films will also be described. Main parts of the research work are listed as follows:(1) New electron donors 1-3b containing two to four TTF nuclei were synthesized and characterized by 1H-NMR, MS and FT-IR.(2) The redox potentials of the new electron donors were measured with cyclic voltammetry and the comparison with ET(bisethylenedithiotetrathiafulvalene) in this respect was made. The results indicated that all of the new electron donors possessed similar electron-donating properties as ET.(3) Both new electron donors 2a and 3a can form stable mono-layer on the air-water interface. The corresponding multi-layer LB films were deposited on various substrates. The room temperature conductivity of the LB films after I2 doping are ranged in 10-7~10-5 S.cm-1. And the absorption spectra, before I2 doping and after I2 doping, were also investigated.Single crystals of four cation radical salts based on an ethylenedisulfanyl linked tetrathiafulvanlene (bis(ethylenedithiotetrathiafulvalenylsulfanyl) -enthane, 4) 4([TCNQF4]2, 4(PF6(CH2Cl2)0.5, 4(AsF6(CH2Cl2)0.5 and 4(BF4 were prepared by chemical oxidation and electrocrystallization. The crystal structures of these salts along with their electrical conducting behaviors are described,. For comparison, the crystal structure of the neutral donor is also reported. In the crysrtal of 4([TCNQF4]2 salt the donor molecules adopt a<WP=8>(4) Z-shape conformation with two TTF moieties loacting at the different side of the bridge, which is similar as what were observed in its neutral crystals. Charges on each TTF moieties are +1, and no continuous (-( overlaps exist in this crystal. This has lead to a insulator behavior of this salt with (rt<10-7Scm-1. The two salts with PF6 and AsF6 are isostructural, in which the donor molecules adopt a U-shape conformation with two TTF moieties loacting at the same side of the bridge. The donor molecules pack into a two-dimensional layer structure with the TTF moieties from different donor molecules forming a dimeric structure, which serve as the conducting path. The stack pattern in the crystal of 4(BF4 is similar as that of 4(PF6(CH2Cl2)0.5 and 4(AsF6(CH2Cl2)0.5. 4(PF6(CH2Cl2)0.5, 4(AsF6(CH2Cl2)0.5 and 4(BF4 display semi-conducting properties from room temperature down to 60 K.更多还原