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Ferrocene Adsorbed on Silica and Activated Carbon Surfaces: A Solid-State NMR Study of Molecular Dynamics and Surface Interactions
Organometallics ( IF 2.5 ) Pub Date : 2020-03-05 , DOI: 10.1021/acs.organomet.9b00800 Patrick J. Hubbard 1 , Jordon W. Benzie 1 , Vladimir I. Bakhmutov 1 , Janet Blümel 1
Organometallics ( IF 2.5 ) Pub Date : 2020-03-05 , DOI: 10.1021/acs.organomet.9b00800 Patrick J. Hubbard 1 , Jordon W. Benzie 1 , Vladimir I. Bakhmutov 1 , Janet Blümel 1
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Ferrocene has been adsorbed on the surface of silica and activated carbon within the pores by dry grinding in the absence of a solvent at room temperature. While the dry adsorption and translational mobility of ferrocene within the pores are already established on the centimeter scale, there is little systematic understanding of the surface site-to-site motions of the ferrocene molecules and their orientation with respect to the surface. In this paper, silica and activated carbon, both widely applied in academia and industry as adsorbents, are used as support materials. Using variable-temperature 13C and 2H solid-state NMR and T1 relaxation time measurements, the dynamics of ferrocene on the surfaces of silica and activated carbon within the pores has been quantitatively characterized on the molecular scale. The obtained data indicate that ferrocene molecules show a liquid-like behavior on the surface. Fast exchange between isotropically moving molecules and surface-attached molecular states of ferrocene has been found in samples with submonolayer surface coverages. The surface-attached molecular states have been characterized by the free energies ΔG⧧ of 6.1 kcal/mol for silica and ΔG⧧ of 6.2 kcal/mol for activated carbon at 223 and 263 K, respectively. The horizontally oriented ferrocene molecules are the most thermodynamically stable states on the surfaces of both materials. These molecules exhibit fast C5 rotation of the Cp rings, as established by low-temperature 13C and 2H NMR. The interactions of ferrocene with the pore surfaces have been characterized by adsorption enthalpies measured as −8.4 to −7.0 kcal/mol and −6.7 kcal/mol for activated carbon and silica, respectively. It has been suggested that the ferrocene–surface interactions for both support materials have a polar character.
中文翻译：
二氧化硅和活性炭表面吸附的二茂铁：分子动力学和表面相互作用的固态NMR研究
在室温下，在无溶剂的情况下，通过干磨将二茂铁吸附在二氧化硅的表面和孔内的活性炭上。尽管二茂铁在孔中的干吸附和平移迁移率已经在厘米尺度上确定，但是对二茂铁分子的表面点到点运动及其相对于表面的取向了解得很少。在本文中，二氧化硅和活性炭均广泛用作学术界和工业界的吸附剂，并被用作支撑材料。使用温度可变的13 C和2 H固态NMR和T 1在弛豫时间测量中，已经在分子尺度上定量表征了二氧化硅表面上的二茂铁动力学和孔内活性炭的动力学。获得的数据表明二茂铁分子在表面上显示出液体状的行为。在具有亚单层表面覆盖的样品中，已经发现各向同性运动的分子与二茂铁的表面附着分子状态之间的快速交换。表面附着的分子态的特点是自由能Δ ģ ⧧ 6.1千卡/摩尔为二氧化硅和Δ ģ ⧧分别为223和263 K时活性炭的6.2 kcal / mol。水平取向的二茂铁分子在两种材料的表面上都是最热力学稳定的状态。这些分子表现出Cp环的快速C 5旋转，这是通过低温13 C和2 H NMR确定的。二茂铁与孔表面的相互作用已经通过吸附焓表征，活性炭和二氧化硅的吸附焓分别为-8.4至-7.0 kcal / mol和-6.7 kcal / mol。已经提出，两种载体材料的二茂铁-表面相互作用都具有极性。
更新日期：2020-04-24
中文翻译：
二氧化硅和活性炭表面吸附的二茂铁：分子动力学和表面相互作用的固态NMR研究
在室温下，在无溶剂的情况下，通过干磨将二茂铁吸附在二氧化硅的表面和孔内的活性炭上。尽管二茂铁在孔中的干吸附和平移迁移率已经在厘米尺度上确定，但是对二茂铁分子的表面点到点运动及其相对于表面的取向了解得很少。在本文中，二氧化硅和活性炭均广泛用作学术界和工业界的吸附剂，并被用作支撑材料。使用温度可变的13 C和2 H固态NMR和T 1在弛豫时间测量中，已经在分子尺度上定量表征了二氧化硅表面上的二茂铁动力学和孔内活性炭的动力学。获得的数据表明二茂铁分子在表面上显示出液体状的行为。在具有亚单层表面覆盖的样品中，已经发现各向同性运动的分子与二茂铁的表面附着分子状态之间的快速交换。表面附着的分子态的特点是自由能Δ ģ ⧧ 6.1千卡/摩尔为二氧化硅和Δ ģ ⧧分别为223和263 K时活性炭的6.2 kcal / mol。水平取向的二茂铁分子在两种材料的表面上都是最热力学稳定的状态。这些分子表现出Cp环的快速C 5旋转，这是通过低温13 C和2 H NMR确定的。二茂铁与孔表面的相互作用已经通过吸附焓表征，活性炭和二氧化硅的吸附焓分别为-8.4至-7.0 kcal / mol和-6.7 kcal / mol。已经提出，两种载体材料的二茂铁-表面相互作用都具有极性。
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