Department of Chemistry, University of Alberta , Edmonton, Alberta, Canada T6G 2G2.
J Phys Chem B. 2013 Oct 31;117(43):13619-30. doi: 10.1021/jp407469f. Epub 2013 Oct 21.
The one-dimensional IR (1D-IR) absorption and IR pump-probe spectra of a hydrogen stretch in a model hydrogen-bonded complex dissolved in a polar solvent confined in spherical hydrophobic cavities of different sizes were simulated using ground-state mixed quantum-classical dynamics. Due to a thorough analysis of key properties of the complex and solvent from equilibrium trajectory data, we were able to gain insight into the microscopic details underlying the spectra. Both the 1D-IR and IR pump-probe spectra manifested the effects of confinement on the relative stabilities of the covalent and ionic forms of the complex through pronounced changes in their peak intensities and numbers. However, in contrast to the 1D-IR spectra, the time-resolved pump-probe spectra were found to be uniquely sensitive to the changes in the molecular dynamics as the cavity size is varied. In particular, it was found that the variations in the time evolutions of the peak intensities in the pump-probe spectra reflect the differences in the solvation dynamics associated with the various forms of the complex in different locations within the cavities. The ability to detect these differences underscores the advantage of using pump-probe spectroscopy for studying nanoconfined systems.
采用基态混合量子经典动力学模拟了溶解在不同大小的球形疏水腔中的极性溶剂中氢键复合物的氢伸缩一维红外（1D-IR）吸收和红外泵浦探测光谱。由于从平衡轨迹数据中对复合物和溶剂的关键性质进行了彻底分析，我们能够深入了解光谱背后的微观细节。1D-IR 和 IR 泵浦探测光谱都通过显著改变它们的峰强度和数量，表现出了受限对复合物共价和离子形式相对稳定性的影响。然而，与 1D-IR 光谱不同，发现时分辨泵浦探测光谱对随腔尺寸变化的分子动力学变化非常敏感。特别是，发现泵浦探测光谱中峰强度的时间演化的变化反映了与腔体内不同位置的复合物各种形式相关的溶剂化动力学的差异。检测这些差异的能力突出了使用泵浦探测光谱学研究纳米受限系统的优势。
