Theoretical Studies On The [M?CH₃OH?_n](M=Li⁺,Na⁺,K⁺,Be²⁺,Mg²⁺,Ca²⁺,n=1?6) Systems

The thesis mainly consists of three parts.Firstly,the structures of[M?CH₃OH?_n](M=Li⁺,Na⁺,K⁺,Be²⁺,Mg²⁺,Ca²⁺,n=1⁶)are optimized by three DFT methods,WB97XD,B3LYP and M062X,with 6-31++G?d,p?basis set,and the stable configurations are obtained by frequency calculations.Then the 6-311++G?2d,2p?basis set was used to obtain the binding energy of the complexes.It can be found that the results of the above three quantum chemical methods are consistent.The solvation free energies in water of[M?CH₃OH?_n](M=Li⁺,Na⁺,K⁺,Be²⁺,Mg²⁺,Ca²⁺,n=1⁶)from B3LYP/6-31++G?d,p?were calculated by three common solvation models,PCM,and CPCM models.With the increases for methanol number n in the complex,the distance between the metal ion and the oxygen atom R_M…O increases and the molecular symmetry are enhanced for the same metal ion.Meanwhile,the polarity and the solubility in water of these systems decreases.And the total binding energy increases with the increasing coordination number of methanol molecules.When the coordination number of methanol is same,with the increasing ionic radius of differnent metal ion,the R_M…O increases and binding energy decreases,and the absolute value of the solvation free energy increases slightly at the same time.However,for the alkali metal and alkaline metal ions in the same period,the methanol clusters of the former are more difficult to dissolve in water than those of the alkaline earth metal ion.In the second part,the minimum energy structures,binding energies and charge distributions of cyclic methanol cluster?CH₃OH?_n?n=3¹2?,[Na?CH₃OH?_n]⁺?n=3⁶?and[K?CH₃OH?_n]⁺?n=5⁸?are studied via ab initio and the atom-bond electronegativity equalization fluctuating charge force field?ABEEM??/MM?.Based on the ab initio results,the ABEEM??/MM fluctuating charge potential functions are constructed and the related parameters are fitted and determined for the above systems.The results of the above systems show that the binding energies and other properties from ABEEM??/MM are more consistent with ab initio values than the commonly used OPLS/AA force field.The average absolute deviation?AAD?of bond length is less than 0.0361?,and the relative root mean square deviations?RRMSD?of bond length,bond angle and binding energy are less than 3.69%,1.62%and 6.58%,respectively.The linear correlation coefficients of the charege distributions of ABEEM??/MM and ab initio are all above 0.99.In the last part,[M?H₂O?](M=Li⁺,Na⁺,K⁺,Mg²⁺,Ca²⁺)systems were studied by the molecular face theory?MFT?.The stable structures have been optimized by MP2/6-31++G?d,p?with keeping different distances between metal ions and oxygen atoms in water fixed.The potential acting on an electron in a molecule?PAEM?and the molecular intrinsic characteristic contour?MICC?are calculated by the ab initio MELD program and a self programming software.Then the molecular faces are calculated and depicted by Matlab software.The contact point between the molecular faces of metal ions and oxygen atoms is determined.The first ionization energy,surface area and volume,D_pb and so on were compared.The order of the distance between the stable structure and the contact-point structure is Mg²⁺>Ca²⁺>Na⁺>K⁺>Li⁺.This distance indicates the decresing interaction between the metal ions with the water as the distance between them increses.Our results also shows that the distance of the in conctact the molecular faces of metal ions and water molecule by using different basis sets is not significant.