双光谱二维异步相关光谱表征分子间相互作用的可行性研究

Application of Two-Trace Two-Dimensional Asynchronous Correlation Spectroscopy in Characterizing Intermolecular Interactions: A Feasibility Study

双光谱二维异步相关光谱(2T2D-异步相关光谱)是一种利用两幅一维光谱创建异步相关光谱的新方法。相对于最少需要三幅一维光谱的传统异步相关光谱, 2T2D-异步相关光谱可简化实验过程,有利于样品昂贵体系的表征。利用数学分析、模拟及实际体系实验对2T2D-异步相关光谱应用于表征分子间相互作用的可行性进行了研究。首先建立一个包含P和Q两种溶质的模拟体系,设定P有光谱峰, Q没有光谱峰。数学分析表明:(1)不正确设置P和Q初始浓度,可导致2T2D-异步相关光谱的强度恒为零;(2) 2T2D-异步相关光谱不能反映与分子间相互作用相关的峰强变化;因此,利用2T2D-异步相关光谱表征分子间相互作用可能得到错误的结论。为将2T2D-异步相关光谱发展成为表征分子间相互作用的可靠方法,首先对2T2D-异步相关光谱中P和Q初始浓度的设置方法进行了研究,得出当P和Q初始浓度满足文中式(6)时,可避免不正确设置P和Q初始浓度导致2T2D-异步相关光谱强度恒为零的情况;在此基础上,为解决2T2D-异步相关光谱不能反映与分子间相互作用相关的峰强变化问题,通过向体系中加入具有独立光谱峰和适合浓度的虚拟物质S,发展出带有辅助交叉峰的2T2D-异步相关光谱(ASAP-2T2D-异步相关光谱)。模拟体系实验表明ASAP-2T2D-异步相关光谱可正确反映与分子间相互作用相关的峰宽、峰位及峰强变化,是表征分子间相互作用的可靠方法。最后,将ASAP-2T2D-异步相关光谱应用于表征苯并-15-冠醚-5(BC)与Li^+间的相互作用,实验结果表明ASAP-2T2D-异步相关光谱可同时反映BC特征峰的峰位及峰强变化,进一步证实ASAP-2T2D-异步相关光谱可正确表征分子间相互作用。

Two-trace two-dimensional(2 T2 D) asynchronous correlation spectroscopy is a new method of generating two-dimensional asynchronous correlation spectroscopy based on a pair of one-dimensional(1 D) spectra. Compared with the conventional two-dimensional asynchronous correlation spectroscopy where at least three 1 D spectra are needed, 2 T2 D asynchronous correlation spectroscopy makes the experiment easier, and is a better method for the expensive samples. In the present paper, the feasibility of using 2 T2 D asynchronous correlation spectroscopy to characterize intermolecular interactions was explored. Firstly, a model system containing two solutes P and Q were set up. P possessed a characteristic peak, and Q had no characteristic peaks. The mathematical analysis demonstrated that the intensity of 2 T2 D asynchronous correlation spectra was always zero when the initial concentrations of P and Q were set incorrectly. Furthermore, the variations of the absorptivity induced by intermolecular interactions could not be discerned by 2 T2 D-asynchronous correlation spectra. Therefore, incorrect results may be obtained when 2 T2 D asynchronous correlation spectroscopy is adopted to characterize intermolecular interactions. In order to develop 2 T2 D asynchronous correlation spectroscopy into a reliable method for characterizing intermolecular interactions, the setting method of the initial concentrations of P and Q in the 2 T2 D asynchronous correlation spectroscopy was first studied. The case that the intensity of 2 T2 D asynchronous correlation spectra was always zero induced by incorrectly setting the initial concentrations of P and Q could be avoided when the initial concentrations of P and Q satisfied the requirement of Eq.(6) in the text. On this basis, the 2 T2 D-asynchronous correlation spectroscopy with auxiliary cross peaks(ASAP-2 T2 D-asynchronous correlation spectroscopy) was developed by introducing a virtual substance S with an isolated peak and proper concentration into the research system to solve the problem that 2 T2 D-asynchronous correlation spectra could not reflect the variations of the absorptivity induced by intermolecular interactions. The results of computer simulation experiments demonstrated that the ASAP-2 T2 D-asynchronous correlation spectra could correctly reflect the variation of the peak position, bandwidth and absorptivity indicating that the ASAP-2 T2 D-asynchronous correlation spectroscopy was a reliable method for characterizing intermolecular interactions. Finally, the ASAP-2 T2 D-asynchronous correlation spectroscopy was adopted to characterize the intermolecular interaction between Li^+ and benzo-15-crown-5(BC). The results demonstrated that the variation of the peak position and absorptivity of the characteristic peak of BC could be reflected by the ASAP-2 T2 D-asynchronous correlation spectrum. These results further confirmed that the ASAP-2 T2 D-asynchronous correlation spectroscopy could correctly characterize intermolecular interactions.