Esser Alexander, Forbert Harald, Marx Dominik
Lehrstuhl für Theoretische Chemie , Ruhr-Universität Bochum , 44780 Bochum , Germany.
Center for Solvation Science ZEMOS , Ruhr-Universität Bochum , 44780 Bochum , Germany.
Chem Sci. 2017 Dec 21;9(6):1560-1573. doi: 10.1039/c7sc04040g. eCollection 2018 Feb 14.
Although bare protonated methane is by now essentially understood at the level of intramolecular large-amplitude motion, scrambling dynamics and broadband vibrational spectra, the microsolvated species still offer plenty of challenges. One aspect is the effect of the attached solvent molecules on the infrared absorption spectra of microsolvated CH complexes compared to the bare parent molecule. In this study we analyze, based on molecular dynamics simulations, protonated methane molecules that have been microsolvated with up to three hydrogen molecules, CH·(H) . In particular, upon introducing a novel multi-channel maximum entropy methodology described herein, we are able to decompose the infrared spectra of these weakly-bound complexes in the frequency window from 1000 to 4500 cm into additive single mode contributions. Detailed comparisons to the bare CH parent reveal that these perturbed modes encode distinct features that depend on the exact microsolvation pattern. Beyond the specific case, such understanding is relevant to assess tagging artifacts in vibrational spectra of parent molecules based on messenger predissociation action spectroscopy.
尽管目前对于裸露的质子化甲烷，在分子内大幅度运动、重排动力学和宽带振动光谱层面已基本了解，但微溶剂化物种仍带来诸多挑战。一个方面是，与裸露的母体分子相比，附着的溶剂分子对微溶剂化CH络合物红外吸收光谱的影响。在本研究中，我们基于分子动力学模拟，分析了用多达三个氢分子微溶剂化的质子化甲烷分子CH·(H) 。特别是，通过引入本文所述的一种新颖的多通道最大熵方法，我们能够将这些弱束缚络合物在1000至4500厘米频率窗口内的红外光谱分解为相加的单模贡献。与裸露的CH母体进行的详细比较表明，这些受扰模式编码了取决于精确微溶剂化模式的独特特征。除了这个特定案例外，这种理解对于基于信使预解离作用光谱评估母体分子振动光谱中的标记伪影也具有重要意义。
