在水相中的相反电荷分子开关的光电子光谱:理论和实验
E Ikonnikov1, M Paolino2, J C Garcia-Alvarez3
1Max Born Institute, Max-Born-Straße 2A, 12489 Berlin, Germany.
The journal of physical chemistry letters
|June 26, 2023
概括
这项研究验证了分子开关水相X射线光电子光谱 (XPS) 的理论模型. 准确的溶解模型对于解释溶液中的电子结构至关重要,特别是对于带电的分子.
科学领域:
- 物理化学 物理化学
- 计算化学计算化学
- 频谱学是一种光谱学.
背景情况:
- 射线光电子谱学 (XPS) 探测分子电子结构.
- 解释凝聚相XPS需要准确的理论解法模型.
- 现有的气相模型无法预测实验水相结合能.
研究的目的:
- 用充电生物模拟分子开关的水相XPS进行理论溶解模型的基准测试.
- 评估隐式和显式溶剂模型在预测电子结合能量转移方面的准确性.
- 研究 counterions 在稳定溶液中充电的分子状态中的作用.
主要方法:
- 在NAIP和p-HDIOP的水相XUV光电子光谱 (XPS) 试验中.
- 使用隐性溶剂模型 (非平衡极化连续模型) 进行理论计算.
- 使用显式溶剂模型进行理论计算,采用平均溶剂静电配置和自由能量梯度 (ASEC-FEG) 方法.
主要成果:
- 实验水相XPS揭示了NAIP和p-HDIOP之间的1.1 eV电子结合能差 (ΔeBE).
- 气相计算预测了8 eV ΔeBE,强调了溶解的重要性.
- 隐式和ASEC-FEG显式溶剂模型都在三个计算协议中准确地复制了实验 ΔeBE.
- ASEC-FEG的计算表明,明确包含的 counterions 对分子状态的稳定作用.
结论:
- 理论上的溶解模型,特别是像ASEC-FEG这样的明确溶剂方法,对于准确解释水相XPS数据至关重要.
- 通过适当的计算方法,可以准确预测溶液中的电子结构变化.
- 在充电的分子系统中,对电离子在调节电子结合能方面发挥着重要作用.
相关概念视频
01:16UV–Vis Spectroscopy: Molecular Electronic Transitions
1.6K
In Ultraviolet–Visible (UV–Vis) spectroscopy, the absorption of electromagnetic radiation is used to probe the electronic structure of molecules. This technique provides insights into molecular electronic transitions, particularly the movement of electrons between different molecular orbitals. Radiation is absorbed if the energy of the electromagnetic radiation passing through the molecule is precisely equal to the energy difference between the excited and ground states. During this...
1.6K
01:14Molecular Spectroscopy: Absorption and Emission
2.4K
Molecules possess discrete energy levels called quantum states. Unlike atoms, which have simpler energy levels, molecules possess additional rotational and vibrational energy levels. Each energy level is separated by an energy gap, with the gaps between adjacent electronic, vibrational, and rotational levels varying significantly. The three types of energy levels in a diatomic molecule are shown in Figure 1.
2.4K
01:27π Electron Effects on Chemical Shift: Overview
1.1K
An applied magnetic field causes loosely bound π-electrons in organic molecules to circulate, producing a local or induced diamagnetic field over a large spatial volume. As the molecules tumble in solution, the field generated by π-electrons in spherical substituents results in a zero net field. However, the net field generated by π-electrons in non-spherical substituents is not zero. The effect of this induced field depends on the orientation of the molecule with respect to B0,...
1.1K
01:26Photochemical Electrocyclic Reactions: Stereochemistry
1.9K
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
1.9K
01:17Electron Paramagnetic Resonance (EPR) Spectroscopy: Organic Radicals
2.6K
Ideally, an unpaired electron shows a single peak in the EPR spectrum due to the transition between the two spin energy states. However, coupling interactions can occur between the spins of the unpaired electron and any neighboring spin-active nuclei. This hyperfine coupling results in hyperfine splitting, where the EPR signal is split into multiplets. The signals split into 2nI + 1 peaks, where n is the number of equivalent nuclei and I is the nuclear spin. These splitting patterns provide...
2.6K
01:14π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds
1.2K
In aromatic compounds, such as benzene, the circulation of (4n + 2) π-electrons sets up a diamagnetic or diatropic ring current around the perimeter of the molecule. This current induces a magnetic field that opposes the external field inside the ring and reinforces it on the outside. The protons in benzene are deshielded and exhibit high chemical shifts in the range 6.5–8.5 ppm. The shielding effect at the center of the ring is evident in complex aromatic molecules, such as...
1.2K