Atifi Abderrahman, Ryan Michael D
Chemistry Department, Marquette University , PO Box 1881, Milwaukee, Wisconsin 53201, United States.
Anal Chem. 2015 Dec 15;87(24):12245-53. doi: 10.1021/acs.analchem.5b03411. Epub 2015 Nov 20.
The presence and effect of RTIL nanodomains in molecular solvent/RTIL mixture were investigated by studying the spectroelectrochemistry and voltammetry of nickel octaethylporphyrin (Ni(OEP)) and nickel octaethylporphinone (Ni(OEPone)). Two oxidation and 2-3 reduction redox couples were observed, and the UV-visible spectra of all stable products in THF and RTIL mixtures were obtained. The E° values for the reduction couples that were studied were linearly correlated with the Gutmann acceptor number, as well as the difference in the E° values between the first two waves (ΔE12° = |E1° - E2°|). The ΔE12° for the reduction was much more sensitive to the %RTIL in the mixture than the oxidation, indicating a strong interaction between the RTIL and the anion or dianion. The shifts in the E° values were significantly different between Ni(OEP) and Ni(OEPone). For Ni(OEP), the E1° values were less sensitive to the %RTIL than were observed for Ni(OEPone). Variations in the diffusion coefficients of Ni(OEP) and Ni(OEPone) as a function of %RTIL were also investigated, and the results were interpreted in terms of RTIL nanodomains. To observe the effect of solvation on the metalloporphyrin, Ni(OEPone) was chosen because it contains a carbonyl group that can be easily observed in infrared spectroelectrochemistry. It was found that the νCO band was very sensitive to the solvent environment, and two carbonyl bands were observed for Ni(OEPone)(-) in mixed THF/RTIL solutions. The higher energy band was attributed to the reduced product in THF, and the lower energy band attributed to the reduced product in the RTIL nanophase. The second band could be observed with as little as 5% of the RTIL. No partitioning of Ni(OEPone)(+) into the RTIL nanodomain was observed. DFT calculations were carried out to characterize the product of the first reduction. These results provide strong direct evidence of the presence of nanodomains in molecular solvent/RTIL mixtures.
通过研究八乙基卟啉镍（Ni(OEP)）和八乙基卟吩镍酮（Ni(OEPone)）的光谱电化学和伏安法，研究了离子液体纳米域在分子溶剂/离子液体混合物中的存在及其影响。观察到两个氧化和2 - 3个还原氧化还原对，并获得了四氢呋喃（THF）和离子液体混合物中所有稳定产物的紫外可见光谱。所研究的还原对的E°值与古特曼受体数以及前两个波之间的E°值差异（ΔE12° = |E1° - E2°|）呈线性相关。还原的ΔE12°对混合物中离子液体的百分比比氧化更敏感，表明离子液体与阴离子或二价阴离子之间存在强相互作用。Ni(OEP)和Ni(OEPone)的E°值变化显著不同。对于Ni(OEP)，E1°值对离子液体百分比的敏感度低于Ni(OEPone)。还研究了Ni(OEP)和Ni(OEPone)的扩散系数随离子液体百分比的变化，并根据离子液体纳米域对结果进行了解释。为了观察溶剂化对金属卟啉的影响，选择了Ni(OEPone)，因为它含有一个羰基，在红外光谱电化学中很容易观察到。发现νCO带对溶剂环境非常敏感，在混合的THF/离子液体溶液中，Ni(OEPone)(-)观察到两个羰基带。能量较高的带归因于THF中的还原产物，能量较低的带归因于离子液体纳米相中的还原产物。仅5%的离子液体就能观察到第二条带。未观察到Ni(OEPone)(+)分配到离子液体纳米域中。进行了密度泛函理论（DFT）计算以表征第一次还原的产物。这些结果提供了分子溶剂/离子液体混合物中存在纳米域的有力直接证据。
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