Spectral Properties And Theoretical Calculation Of Salt Solutions System (M=Li,K,Mn)

The study of micro structure and properties in salt solutions is still one of the highlight issues at present.Salt usually exists in the form of ions in the solution,and forms a variety of configurations with the interaction with the solvent.It could exert an effect on inducing the vibration of various bonds of the solvent molecules,which brings changes to the group frequency,thus affecting the spectral properties of the solvent.The study on the microscopic nature of the solution through changes of the spectrum,therefore,is of great guiding significance for the development of biochemistry.In this paper,different salt solution systems were studied through combing various experimental spectroscopy techniques with the calculation of quantum chemistry theory on the basis of the previous work,and water and DMSO were chosen as the target solvents.The main contents are as follows:The hydrated clusters[M?H₂O?_n]⁺?M=Li,K?were studied by Mass spectra,Raman spectra and theoretical calculation.The ion peaks of hydrated clusters of[M?H₂O?_n]⁺?M?Li,K?were analyzed by mass spectra,and thus the maximum hydration number in aqueous solution was deduced.The LiCl and KCl aqueous solutions with the same concentration and gradient were discussed and compared,and the linear rule and strength of hydration of Li+ and K+ in the solution were obtained by Raman spectra.Theoretical calculation of the[M?H₂O?_n]⁺ hydrated cluster structure and the theoretical Raman spectra showed that Li+,K+ formed the second hydration layer under the condition of n>4 and n>6,the blue shift happened on the frequency of O-H stretching vibration,and hydrogen bond structure was destroyed,which were consistent with the experimental results.The MnCl₂/DMSO solutions at different concentrations and temperatures were analyzed by Raman spectra,which showed that the solvation of Mn²⁺ had a great effect on S=O and C-S stretching vibration of DMSO characteristic peaks.Among the range of 0-0.8 mol·L^-1.if the concentration increased,the interaction between Mn²⁺ and DMSO gradually increased.Besides,the rise of temperature would weaken solvation and the temperature could impose a greater influence on solvation than association of solvent.In addition,manganese salt could rapidly diminish the fluorescence peak of DMSO and if the concentrations of manganese salt are high,the peak will basically disappear.Moreover,the optimized possible solvation configurations[Mn?DMSO?_n]²⁺,therrmodynamic properties,and the theoretical Raman spectra were calculated by density functional theory,consisting with the results of the experimental spectrum.Changes of DMSO/H₂O double solvents and the influence of Li+ to it were respectively discussed by experimental spectra.It was found that the existence of a large number of water molecules made C-S and C-H bonds weaken,S=O double bond strengthen,and fluorescence of DMSO quenching.A large number of DMSO molecules made O-H bond weaken and thus great changes happened on various hydrogen bond structures.Added lithium salt affected the internal structure of DMSO/H₂O double solvents,and Lithium salt with high concentration weakened the fluorescent efficiency of DMSO/H₂O.At the same time,ultraviolet absorption peak intensity would be enhanced with the increase of Lithium concentration.Part of the solvent molecule configurations and Li⁺ solvation configurations were obtained by using the density functional theory,confirming that experimental results are reliable and speculation is reasonable.