Chisholm Malcolm H, Patmore Nathan J
Department of Chemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, Ohio 43210-1185, USA.
Chem Rec. 2005;5(5):308-20. doi: 10.1002/tcr.20053.
The reaction of M2(O2CBu(t))4 (M = Mo, W) with a dicarboxylic acid in toluene yields compounds of general formula [M2]-O2C-X-CO2-[M2] ([M2] = M2(O2CBu(t))3; X = conjugated spacer). The M2 units are electronically coupled via interactions between the M2 delta and dicarboxylate pi* orbitals, and the magnitude of this coupling is revealed by electronic structure calculations and spectroscopic data. These compounds show intense metal to ligand charge transfer (MLCT) absorptions in the visible region of the electronic spectrum that are temperature and solvent dependent. Evidence of electronic coupling is seen in their cyclic voltammograms, which show two successive one-electron oxidations. The extent of electronic coupling in the mixed valence radical cations [M2]-O2C-X-CO2-[M2]+, generated by oxidation with one equivalent of AgPF6 or FeCp2PF6, is evaluated by EPR and UV-vis-NIR spectroscopic data, and delocalized behavior is observed in compounds with W2 units separated by up to 13.6 angstroms. The simplicity of the frontier M2 orbital interactions with the bridge pi orbitals provides a convenient system with which to study electron transfer in mixed valence systems, as compared to the extensively studied, but more complicated, dinuclear t(2g)6/t(2g)5 mixed valence compounds. Oligomeric and polymeric compounds incorporating M2 units have also been synthesized, having general formula [M2(O2CR)2(O2C-Thio-CO2)]n (Thio = n-hexyl substituted ter- and quinque-thiophenes). They can be deposited as thin films by spin coating, and show photoluminescence and electroluminescence. These metallo-polythiophenes show potential for application in electronic materials. (
M2(O2CBu(t))4（M = Mo，W）与二元羧酸在甲苯中反应生成通式为[M2]-O2C-X-CO2-[M2]的化合物（[M2] = M2(O2CBu(t))3；X = 共轭间隔基）。M2单元通过M2 δ轨道与二羧酸根π*轨道之间的相互作用实现电子耦合，这种耦合的大小通过电子结构计算和光谱数据得以揭示。这些化合物在电子光谱的可见光区域表现出强烈的金属到配体电荷转移（MLCT）吸收，其吸收依赖于温度和溶剂。在它们的循环伏安图中可以看到电子耦合的证据，该图显示了两个连续的单电子氧化过程。通过EPR和紫外可见近红外光谱数据评估了用一当量的AgPF6或FeCp2PF6氧化生成的混合价自由基阳离子[M2]-O2C-X-CO2-[M2]+中的电子耦合程度，并且在W2单元间隔达13.6埃的化合物中观察到了离域行为。与广泛研究但更复杂的双核t(2g)6/t(2g)5混合价化合物相比，前沿M2轨道与桥π轨道相互作用的简单性为研究混合价体系中的电子转移提供了一个便利的系统。还合成了包含M2单元的低聚和聚合化合物，其通式为[M2(O2CR)2(O2C-Thio-CO2)]n（Thio = 正己基取代的三噻吩和五噻吩）。它们可以通过旋涂沉积成薄膜，并表现出光致发光和电致发光。这些金属聚噻吩在电子材料中有应用潜力。
