Toward Ionic-Liquid-Based Model Catalysis: Growth, Orientation, Conformation, and Interaction Mechanism of the [Tf2N]- Anion in [BMIM][Tf2N] Thin Films on a Well-Ordered Alumina Surface
Toward Ionic-Liquid-Based Model Catalysis: Growth, Orientation, Conformation, and Interaction Mechanism of the [Tf2N]- Anion in [BMIM][Tf2N] Thin Films on a Well-Ordered Alumina Surface
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DOI：
10.1021/la904319h
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发表时间：
2010-05-18
期刊：
影响因子：
3.9
通讯作者：
Libuda, Joerg
中科院分区：
文献类型：
--
作者：
Sobota, Marek;Nikiforidis, Ioannis;Libuda, Joerg
为了更好地理解离子液体（IL）薄膜与氧化物载体的相互作用，我们在超高真空（UHV）条件下进行了模型研究。我们采用红外反射吸收光谱（IRAS）结合密度泛函理论（DFT）。利用一种新型的与超高真空兼容的蒸发器在NiAl（110）衬底上的原子级平整、有序的氧化铝膜上生长了1-丁基-3-甲基咪唑双（三氟甲基磺酰基）酰亚胺[BMIM][Tf 2N]薄膜。时间分辨IRAS测量过程中的增长和随后的热解吸点可逆的分子吸附和解吸。没有腐烂的迹象。借助I）FT计算对振动带进行了归属。在单层区域中观察到单个[Tf 2N]（-）条带的强相对强度变化。这表明阴离子具有明显的取向效应。通过与DEL的详细比较，确定了[Tf_2N]（-）的吸附几何构型。结果表明，[Tf_2N]（-）阴离子在亚单分子层区域采用顺式构象。它们以相对于表面略微倾斜的方向吸附，主要通过磺酰基与载体相互作用。
Aiming at a better understanding of the interaction of ionic liquid (IL) thin films with oxide supports, we have performed a model study under ultrahigh vacuum (UHV) conditions. We apply infrared reflection absorption spectroscopy (IRAS) in combination with density functional theory (DFT). Thin films of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIM][Tf2N] are grown on an atomically flat, well-ordered alumina film on NiAl(110) using a novel UHV-compatible evaporator. Time-resolved IRAS measured during the growth and subsequent thermal desorption points toward reversible molecular adsorption and desorption. There was no indication of decomposition. The vibrational bands are assigned with the help of I) FT calculations. Strong relative intensity changes in individual [Tf2N](-) bands are observed in the monolayer region. This indicates pronounced orientation effects for the anion. The adsorption geometry of [Tf2N](-) is determined on the basis of a detailed comparison with DEL The results suggest that [Tf2N](-) anions adopt a cis conformation in the submonolayer region. They adsorb in a slightly tilted orientation with respect to the surface, mainly interacting with the support via the sulfonyl groups.