质谱和拉曼光谱对[M(H2O)n]+(M=Li,K)水合团簇的研究

Study on [M(H_2O)_n]^+(M=Li,K) Hydrated Clusters by Mass and Raman Spectra

采用质谱、拉曼光谱及理论计算对[M(H_2O)_n]^+(M=Li,K)水合团簇进行了研究。质谱分析[M(H_2O)_n]^+(M=Li,K)水合团簇的离子峰,推测其水溶液中最大水化数为12和13。采用拉曼光谱对浓度梯度相同的LiCl和KCl水溶液进行了讨论与比较,Li^+和K^+的水化作用导致~3 208cm^(-1)水结构拉曼峰发生了明显的变化,其中LiCl和KCl溶液的浓度分别在0~2.0和0~2.5mol·L^(-1)范围内,水化作用呈线性增强,浓度大于2.0和2.5mol·L^(-1)时,偏离线性关系,出现缔合。理论计算[M(H_2O)_n]^+水合团簇结构和理论拉曼光谱表明,Li^+,K^+分别在n>4和n>6开始第二水化层,O—H伸缩振动频率发生了蓝移,氢键结构遭到了破坏,与实验结果一致。

[M(H 2O)n]+(M=Li,K)hydrated clusters have been studied byMass spectra,Raman spectra and the theoretical calculation.[M(H 2O)n]+(M=Li,K)hydrated clusters ion peaks could be obtained by Mass spectra,which could speculate that their maximum hydration numbers are 12 and 13 in their aqueous solution respectively.The same concentration gradient LiCland KCl aqueous solutions of Raman spectra have been discussed and compared,the^3 208 cm-1 Raman spectra of water structure had obvious changes because of the hydration of Li+and K+.Between the 0~2.0 and 0~2.5 mol·L-1 concentration range of LiCl and KCl aqueous solution,respectively,their differential Raman spectra of^3 208 cm-1 negative peak integral strength decreased in a linear,and hydration increased gradually.While concentration was more than 2.0 and 2.5 mol·L-1,the decrease of^3 208 cm-1negative peak integral strength deviated from linear relationship,and began toappear association.Theoretical calculation of structure and Raman spectra of[M(H 2O)n]+(M=Li,K)hydrated clusters showed that Li+andK+would form their second hydrated layer while n>4 and n>6 respectively,and O-H stretching vibration occurred blue shift,hydrogen bonding structures should been destroyed,thus was in agreement with the experimental results.