温度扰动下CuCl2/DMF溶液的二维相关拉曼光谱分析

Two-Dimensional Correlation Raman Spectroscopic Analysis of CuCl2/DMF Solution Under Temperature Disturbance

溶液的光谱研究一直受到化学工作者的关注,但大多研究是以一维光谱技术为主,存在分辨率低,误差较大,重叠峰难以分辨等诸多弊端,无法清晰地给出需要的信息。二维光谱通过对外部扰动下的动态光谱进行相关分析计算,从而得到光谱强度的整体变化信息,显著提高一维光谱的分辨率以及重叠峰的分离度。在判断特定外扰下不同官能团的响应次序以及研究分子间、分子内的弱相互作用上具有独特优势。采用二维相关拉曼光谱和理论计算相结合,对溶液内微观团簇及其变化进行了研究。利用显微共焦激光拉曼光谱仪对目标溶液(纯DMF与0.84 mol·L^-1的CuCl2/DMF溶液)进行了升温实验。结果发现在C—N键伸缩振动谱带范围内,由于CuCl2的加入,特征峰强度整体大幅下降,峰宽变大,在1115 cm^-1有新峰产生,随温度升高,伸缩振动峰强度逐渐下降,峰形变缓。为了获得C—N键振动内各特征峰随温度的变化情况,采用移动窗口二维拉曼(MW2D Raman)光谱技术,对光谱数据进行分析。结果表明溶液内不同类别的微观团簇对温度的敏锐程度不同,随温度升高,它们之间存在相互转化,且变化速度不同。为了获取溶液内各微观团簇运动的实质,以温度为外扰,采用二维拉曼(2D Raman)光谱对目标溶液进行分析,通过对二维光谱中特征峰进行归属和变化次序判断,发现金属Cu^2+的加入,使得溶液体系变得更加复杂,除存在原溶剂内所含的团簇构型,还存在与Cu^2+发生溶剂化的团簇构型,它们之间存在着一定的相互转化。利用密度泛函理论对溶液中可能存在的团簇构型进行结构优化和热力学计算,结果证实了Cu^2+与DMF存在相互作用,且由此产生的团簇构型[Cu(DMF)n]^2+(n=1~6)的稳定性随n的增大逐渐变差,进一步验证了二维相关光谱分析的可行性与正确性。

The spectroscopic study of the solution has always attracted the attention of chemists,but most of them are based on one-dimensional spectroscopy.There are many disadvantages,such as low resolution,greatly affected by the error,overlapping peaks are difficult to distinguish and so on.So that we cannot get the information we need clarification.These problems were well solved by the introduction of two-dimensional correlation spectroscopy.By correlation analysis and calculation of dynamic spectra under external disturbances,the overall change information of spectral intensity can be obtained,which can significantly improve the resolution of one-dimensional spectroscopy and the separation degree of overlapping peaks.It has unique advantages in judging the response order of different functional groups under specific external disturbance and studying the weak intermolecular and intramolecular interactions.In this article,two-dimensional correlation Raman spectroscopy and theoretical calculation have been combined to the analysis of the micro clusters in solution.The target solution(pure DMF and CuCl2/DMF solution of 0.84 mol·L^-1)was studied by micro confocal laser Raman spectrometer.The results have shown that,in the range of C—N bond stretching vibration band,due to the addition of CuCl2,thestrength of the characteristic peak decreases greatly,and the peak width becomes large.Furthermore,it could be found that there is a new peak at 1115 cm^-1,With the rise of temperature,the strength of stretching vibration peak decreases gradually,and the peak shape becomes slow.It is concluded that different types of micro clusters have different sensitivity to temperature with the help of moving-window two-dimensional Raman(MW2D Raman)spectroscopy.in addition,with the increase of temperature,they transform into each other and change at different rates.In order to obtain the essence of the micro cluster movement in the solution,the target solution was analyzed by two-dimensional Raman(2D Raman)spectroscopy with temperature as the external disturbance.It is found that the addition of Cu^2+ makes the solution system more complex.In addition to the cluster structure existing in the original solvent,there is also the cluster structure solvated with Cu^2+,and there is a certain transformation between them.Furthermore,the optimized possible cluster structures and thermodynamic data were calculated by densityfunctional theory.The results confirmed the interaction between Cu^2+ and DMF,and the stability of the cluster configurations[Cu(DMF)n]^2+(n=1~6)gradually deteriorated with the increase of n.The feasibility and correctness of two-dimensional correlation spectroscopy analysis are verified.