A neutral mixed-valent conducting polymer formed by electron transfer between metal d and ligand π orbitals
A neutral mixed-valent conducting polymer formed by electron transfer between metal d and ligand π orbitals
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DOI：
10.1002/anie.200501189
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发表时间：
2005-01-01
影响因子：
16.6
通讯作者：
Toriumi, K
中科院分区：
文献类型：
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作者：
Mitsumi, M;Goto, H;Toriumi, K
近年来，由单组分分子组成的导电体系引起了人们的广泛关注。[1-3]这些研究将为分子电子器件开发基础技术。小林及其同事报道了[Ni（tmdt）2] 1（tmdt= trimethylenetetrathiafulvalenedithiolate）的晶体是具有3D π带的单组分分子金属，其是基于非常小的HOMO-LUMO带隙以及由HOMO和LUMO形成的交叉带而设计的。[1]另一方面，已经制备了许多直接键合的无限长MPERM链化合物，但具有含金属主链的单组分分子导体尚未报道。[4，5]当通过自下而上的方法构建这种材料时，前沿轨道工程对于获得所需的物理性质和/或功能非常重要。氧化还原活性的二氧戊环衍生物可以通过两个连续的单电子转移产生苯醌（BQ）、半醌（SQC）和儿茶酚（cat 2）的氧化还原异构体。含有这些二氧杂环戊烯配体的几种过渡金属配合物在金属d的前线轨道和二氧杂环戊烯配体π轨道之间具有非常接近的能级，并且在称为价态互变异构的热平衡中在金属和配体之间发生分子内电子转移。[6]另一方面，铑（i）半醌配合物[Rh（3，6-dbsq）（CO）2] 1（3，6-dbsq= 3，6-二叔丁基-1，2-苯并半醌）被报道形成具有直接Rh-Rh相互作用的直链结构。[7]虽然该化合物没有显示出价态互变异构现象，但富电子铑（i）核和缺电子半醌配体的能级被认为是相对接近的。如果配位体π*（SQC）轨道的能级可以被调整到接近或等于由金属dz 2轨道组成的1D d带的能级，则铑（i，ii）半醌/儿茶酚混合价态将通过金属和配位体之间的分子内电子转移实现（图1）。这种方法可能是一个基本的方法，为开发新的中性混合价导电聚合物与含金属骨架的金属配合物。最近，我们通过对配体进行化学修饰，成功地控制了金属配合物中前线轨道的能级。金属和配体之间实现了电子转移，并确定了直接键合的无限MPERM链的混合价态。本文报道了一种新型的直链混合价铑（i，ii）半醌/邻苯二酚配合物[Rh（3，6-dbdiox-4，5-Cl 2）（CO）2] 1（1），其中3，6-dbdiox-4，5-Cl 2表示3，6-二叔丁基-4，5-二氯-1，2-苯并半醌（3，6-dbsq-4，5-Cl 2Cl 2）或3，6-二叔丁基-4，5-二氯邻苯二酚（3，6-dbcat-4，5-Cl 2Cl 2）状态。通过[Rh_4（CO）_（12）]与3，6-二叔丁基-4，5-二氯-1，2-苯醌[8]在正戊烷中的氧化还原反应，得到1的黑色针状晶体。[9]与铑（i）络合物[Rh（3，6-dbsq）（CO）2] 1的光谱相比，1的X射线光电子能谱（XPS）显示出宽的Rh 3d 5/2和3d 3/2信号。1的信号被很好地分辨为Rh+3d 5/2，3/2和Rh 2 + 3d 5/2，3/2双峰（图2），这清楚地表明，1在快速XPS时间尺度上（约...
Recently, conducting systems that consist of a single-component molecule have attracted much attention.[1–3] These studies should develop basic technology for molecular electronic devices. Kobayashi and co-workers reported that a crystal of [Ni (tmdt) 2] 1 (tmdt= trimethylenetetrathiafulvalenedithiolate) is a single-component molecular metal with a 3D π band, which was designed on the basis of a very small HOMO–LUMO gap and crossing bands formed by the HOMO and LUMO.[1] On the other hand, many directly bonded infinite MÀM chain compounds have been prepared, but a single-component molecular conductor with a metalcontaining backbone has yet to be reported.[4, 5] When building such a material by the bottom-up method, frontier-orbital engineering is very important for obtaining the desired physical properties and/or functionalities. Redoxactive dioxolene derivatives can create redox isomers of benzoquinone (BQ), semiquinonate (SQCÀ), and catecholate (cat2À) by two sequential one-electron transfers. Several transition-metal complexes that contain these dioxolene ligands have very close energy levels between the frontier orbitals of the metal d and dioxolene ligand π orbitals, and intramolecular electron transfer occurs between the metal and the ligand in a thermal equilibrium known as valence tautomerism.[6] On the other hand, the rhodium (i) semiquinonato complex [Rh (3, 6-dbsq)(CO) 2] 1 (3, 6-dbsq= 3, 6-ditert-butyl-1, 2-benzosemiquinonate) was reported to form a linear-chain structure with a direct RhÀRh interaction.[7] Although this compound does not show valence tautomerism, the energy levels of the electron-rich rhodium (i) core and the electron-deficient semiquinonato ligand are considered to be relatively close. If the energy level of the ligand π*(SQCÀ) orbital can be adjusted to be close to or the same as the energy level of the 1D d band, which is comprised of metal dz2 orbitals, a rhodium (i, ii) semiquinonato/catecholato mixedvalent state would be achieved by intramolecular electron transfer between metal and ligand (Figure 1). This approach may be a fundamental methodology for the development of novel neutral mixed-valent conducting polymers with metalcontaining backbones based on metal complexes. Recently, we successfully controlled the energy level of the frontier orbitals in the metal complex by chemically modifying the ligand. Electron transfer was realized between metals and ligands, and a mixed-valent state of the directly bonded infinite MÀM chain was ascertained. Herein, we report the synthesis, crystal structure, and electronic properties of the novel linear-chain mixed-valent rhodium (i, ii) semiquinonato/catecholato complex [Rh (3, 6-dbdiox-4, 5-Cl2)(CO) 2] 1 (1), in which 3, 6-dbdiox-4, 5-Cl2 indicates the 3, 6-di-tert-butyl-4, 5-dichloro-1, 2-benzosemiquinonate (3, 6-dbsq-4, 5-Cl2C À) or 3, 6-di-tert-butyl-4, 5-dichlorocatecholate (3, 6-dbcat-4, 5-Cl2 2À) state. This compound is the first example of a neutral mixed-valent conducting polymer with a metal-containing backbone in which the mixed-valent state is formed by electron transfer between metal d and ligand π* orbitals.Black needle crystals of 1 were obtained by a redox reaction of [Rh4 (CO) 12] with 3, 6-di-tert-butyl-4, 5-dichloro-1, 2-benzoquinone [8] in n-pentane.[9] The X-ray photoelectron spectrum (XPS) of 1 exhibits broad Rh 3d5/2 and 3d3/2 signals compared to the spectrum of the rhodium (i) complex [Rh (3, 6-dbsq)(CO) 2] 1. The signals of 1 are well resolved into Rh+ 3d5/2, 3/2 and Rh2+ 3d5/2, 3/2 doublets (Figure 2), which clearly reveal that 1 exists in the mixedvalent state composed of Rh+ and Rh2+ on the rapid XPS timescale (ca …