Sexithiophenes Mediated by MM Quadruple Bonds: MM = Mo2, MoW, and W2

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• 作者：Brian G. Alberding ; Malcolm H. Chisholm ; Yagnaseni Ghosh ; Terry L. Gustafson ; Yao Liu ; Claudia Turro
• 刊名：Inorganic Chemistry
• 出版年：2009
• 出版时间：September 7, 2009
• 年：2009
• 卷：48
• 期：17
• 页码：8536-8543
• 全文大小：951K
• 年卷期：v.48,no.17(September 7, 2009)
• ISSN：1520-510X

文摘

The reactions between MM(TiPB)₄, where TiPB = 2,4,6-triisopropylbenzoate and MM = MoW and W₂, and the (2,2′:5′,2′′-terthiophene)-5-carboxylic acid, TThH (2 equiv) leads to the formation of new compounds trans-MM(TiPB)₂(TTh)₂, II and III, respectively, as well as to the previously reported compound I, when MM = Mo₂. The compounds have been characterized by elemental analysis, ¹H NMR spectroscopy, electronic absorption, and emission spectroscopies together with cyclic voltammetry and differential pulse voltammetry. Calculations on the model compounds I′, II′, and III′, where formate ligands substitute for TiPB, have been carried out employing density functional theory (DFT) and time-dependent DFT. These complexes display intense ¹MLCT absorptions (MMδ to thienyl carboxylate) and have oxidations and reductions that are metal (MMδ) and thienyl ligand based, respectively. All compounds show emission in the near-IR region. At low temperature the NIR emission from I and II shows clear evidence of vibronic features due to υ(MM) 350−390 cm⁻¹, and all compounds show evidence of a vibronic feature due to υ(CO₂) 1200 cm⁻¹. Transient absorption spectroscopy reveals relatively short-lived S₁ states, τ 10 ps, and longer lived T₁ states: τ 72 μs for I, 160 ns for II, and 90 ns for III. The chemistry described here reveals the remarkable influence of MMδ to TTh π electronic coupling on the optoelectronic properties of the thienyl chains.