Sakhtemanian Leila, Duwadi Anjeeta, Baldelli Steven, Ghatee Mohammad Hadi
Department of Chemistry, Shiraz University, 71946, Shiraz, Iran.
Department of Chemistry, University of Houston, Houston, TX, 77204-5003, USA.
Sci Rep. 2024 Oct 5;14(1):23220. doi: 10.1038/s41598-024-74561-8.
Molecular dynamics (MD) simulation of the green ionic liquid [C₄mim][PF₆] mixed with polar benzonitrile (BNZ) solvent provides detailed insights into their structural and dynamic properties, essential for electrochemistry and materials science applications. The simulations we carried out at varying mole fractions (X) reveal the mixtures' physical, structural, and dynamic properties, with radial, spatial, and combined distribution functions, highlighting the effective interaction through H-bonding involved. The simulation indicates that BZN stacks on the cation butyl tail, providing a significant explanation for the unique experimental observations (following). Adding BZN causes the mixture's liquid dynamics to increase linearly at low X and exponentially at high X, with a notable singular transition at 0.5X. Comprehensive efforts were made to verify and support experimental sum frequency generation (SFG) spectroscopy by simulating the surface structure of the mixtures. Consequently, the simulated BZN stacking structure explains (1) the absence of the C≡N vibrational mode in the SFG spectrum for X < 0.8, and (2) the gradual diminishing of the CH SFG signal, which disappears as X approaches 0.5. Finally, this research removes a persistent ambiguity, proving that only the molecular moieties on the surface generate the SFG vibrational signal, while those in the subsurface do not.
对绿色离子液体[C₄mim][PF₆]与极性苯甲腈（BNZ）溶剂混合体系进行分子动力学（MD）模拟，能够深入了解其结构和动力学性质，这对于电化学和材料科学应用至关重要。我们在不同摩尔分数（X）下进行的模拟揭示了混合物的物理、结构和动力学性质，通过径向、空间和组合分布函数，突出了通过氢键参与的有效相互作用。模拟表明，BNZ堆积在阳离子的丁基尾部，这为后续独特的实验观察结果提供了重要解释。添加BNZ会使混合物的液体动力学在低X时线性增加，在高X时呈指数增加，在0.5X处有明显的奇异转变。我们通过模拟混合物的表面结构，做出了全面的努力来验证和支持实验和频产生（SFG）光谱。因此，模拟的BNZ堆积结构解释了：（1）对于X < 0.8，SFG光谱中不存在C≡N振动模式；（2）CH SFG信号逐渐减弱，在X接近0.5时消失。最后，这项研究消除了一个长期存在的歧义，证明只有表面的分子部分产生SFG振动信号，而次表面的分子部分则不会。
