首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Rapid Molecular Motion of Pyrene and Benzene Moieties Covalently Attached to Silica Surfaces
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Rapid Molecular Motion of Pyrene and Benzene Moieties Covalently Attached to Silica Surfaces

机译:共价结合到二氧化硅表面的Sil和苯部分的快速分子运动

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Remarkably large rotational diffusion rates have been determined for silica-attached 1-pyrene at the solid/air interface through time-dependent fluorescence anisotropy measurements. Diffusion rates D_∥ and D_⊥ were determined to be 4 * 10~6 and 2 * 10~6 s~(-1), respectively, by treating the motion of the attached moiety as an oblate ellipsoid of rotation. ~(13)C NMR measurements on solid, silica-attached benzene-1-~(13)C, acquired using conventional solution NMR methods, gave remarkable, high-resolution spectra. A lower limit for the rate of phenyl group motion was estimated to be 1.5 * 10~5 s~(-1), consistent with the fluorescence anisotropy data measured for silica-attached 1-pyrene. Molecular mechanics models for phenyl attached to representative silanol surfaces predict rotational barriers for phenyl rotations in the 2-5 kcal/mol range.
机译:通过与时间有关的荧光各向异性测量,已确定固/气界面处附着有二氧化硅的1- 1-的旋转扩散速率非常大。通过将附着部分的运动视为扁椭圆形旋转,将扩散率D_∥和D_⊥分别确定为4 * 10〜6和2 * 10〜6 s〜(-1)。使用常规溶液NMR方法在固体,二氧化硅连接的苯-1-〜(13)C上进行〜(13)C NMR测量,得出了显着的高分辨率光谱。苯基基团运动速率的下限估计为1.5 * 10〜5 s〜(-1),这与二氧化硅附着的1-py的荧光各向异性数据一致。附着在代表性硅​​烷醇表面上的苯基的分子力学模型预测了在2-5 kcal / mol范围内苯基旋转的旋转势垒。

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