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首页> 外文期刊>Chemistry: A European journal >Intramolecular Mixed-Valence State Through Silicon or Germanium Double Bridges in Rigid Bis(Tetrathiafulvalenes)
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Intramolecular Mixed-Valence State Through Silicon or Germanium Double Bridges in Rigid Bis(Tetrathiafulvalenes)

机译：刚性双（四硫富瓦烯）中硅或锗双桥的分子内混合价态

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摘要

The synthesis and characterization of two ortho-dimethyltetrathia-fulvalene(o-DMTTF)-based rigid dimers containing dimethylsilicon(Me2Si)or dimethylgermanium(Me2Ge)linkers are described.Single-crystal X-ray analysis reveals planar geometry for the central 1,4-disilicon or 1,4-digermanium six-membered rings.DFT calculations provide optimized conformations in agreement with the experimental ones,and also emphasize the role of the heteroatomic linkers in the conjugation between the two redox active units.Cyclic voltammetry measurements show sequential oxidation into radical cation,and then dication species.Solution EPR measurements on the radical-cation species indicate full delocalization of the unpaired electron over both electroactive TTF units,with an associated coupling of 0.42 G with twelve equivalent protons.DFT calculations afford fully planar geometry for the radical-cation species and confirm the experimental isotropic coupling constant.Single-crystal X-ray analyses of two charge-transfer compounds obtained upon chemical oxidation,formulated as [(Me2Si)2(o- DMTTF)2]·1/2[TCNQ]·1/2[TCNQF4] and [(Me2Ge)2(o-DMTTF)2]·[TCNQ], demonstrate the occurrence of genuine mixed-valence radical-cation species,as well as a three-dimensional network of short S...S intermolecular contacts. Temperature-dependent conductivity measurements demonstrate semicon ducting behavior for both charge-trans fer compounds,with an increase of the absolute value of the conductivity upon applying external pressure.Band struc ture calculations reveal peculiar pseudo-two-dimensional electronic structures,also confirming electronic interactions through SiMe2 and GeMe2 bridges.
机译：描述和描述了两个含二甲基硅（Me2Si）或二甲基锗（Me2Ge）连接基的邻二甲基四硫杂富富烯（o-DMTTF）基刚性二聚体。单晶X射线分析揭示了中心1,4的平面几何形状-二硅或1,4-二锗六元环。DFT计算提供了与实验吻合的优化构象，同时强调了杂原子连接子在两个氧化还原活性单元之间共轭中的作用。循环伏安法测量显示顺序氧化溶液中的EPR测量表明，未成对电子在两个电活性TTF单元上都完全离域，相关联的耦合有0.42 G和十二个等效质子。DFT计算提供了完全平面几何形状自由基阳离子种类并确定实验各向同性的耦合常数。两个电荷的单晶X射线分析通过化学氧化获得的电子转移化合物，计算为[（Me2Si）2（o- DMTTF）2]·1/2 [TCNQ]·1/2 [TCNQF4]和[（Me2Ge）2（o-DMTTF）2] ·[TCNQ]，证明了真正的混合价自由基阳离子物种的出现，以及短S ... S分子间接触的三维网络。随温度变化的电导率测量结果表明，两种电荷转移化合物的半导体行为都随着施加外压而增加，电导率的绝对值增加。能带结构计算显示出奇异的伪二维电子结构，也证实了电子相互作用通过SiMe2和GeMe2桥。

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