Theoretical Studies Of Li⁺、Na⁺、K⁺、Be²⁺、Mg²⁺、Ca²⁺ Interact With Methanol

Li⁺、Na⁺、K⁺、Be²⁺、Mg²⁺and Ca²⁺are indispensable components in our living environment,and they participate and facilitate in many essential biological processes.The interactions of metal ions with organic molecules have gained widespread attentions.In this dissertation,the interactions of Li⁺/Na⁺/K⁺/Be²⁺/Mg²⁺/Ca²⁺and methanol were studied by quantum chemical method and the atom-bond electronegativity equalization fluctuating charge model（ABEEM/MM）.Firstly,the structures of M（CH₃OH）_n=1⁶(M=Li⁺/Na⁺/K⁺/Be²⁺/Mg²⁺/Ca²⁺)were optimized and the zero point energy were calculated by MP2/6-31++G（d,p）method,then the energies of stable conformations were calculated at the MP2/6-311++G（2d,2p）level with BSSE correction.Results show the most stable configuration of M（CH₃OH）_n=1⁶=1⁶ is that the metal cation binds at the site of O atom of methanol,forming a 4-fold coordinated complex for Li⁺/Na⁺/Be²⁺and a 6-fold coordinated complex for K⁺/Mg²⁺/Ca²⁺.With the increasing ligand methanol number,the distance between the cation and the oxygen atom of methanol R_M-O-O and the binding energy increases gradually,while the successive binding energy and the positive charge of metal cation reduces,for the same ligand number,the order of the magnitude of charge transfer is Li⁺>K⁺>Na⁺,Be²⁺>Ca²⁺>Mg²⁺.For the atoms of methanol,the order of the magnitude of charge transferred to is H（-HO）>H（-H3C）>C>O,but the order is H（-HO）>H（-H3C）>O>C of the Li⁺（CH₃OH）_n=1⁶.Secondly,in the spirit of ABEEMσπ/MM,the valence electronegativity and valence state hardness of methanol,Na⁺,K⁺,Mg²⁺and Ca²⁺of（CH₃OH）_n=3⁶,Na⁺（CH₃OH）_n=4⁶=4⁶ and K⁺/Mg²⁺/Ca²⁺（CH₃OH）_n=6⁸=6⁸ were reparameterized by fitting the structures,charge distributions and binding energies from ab inito calculations,andtwo potential energy functions were constructed to describe the interactions of methanol molecules with metal ions and methanol molecules,respectively.Results show that,compered with the MP2 results for Na⁺/K⁺/Mg²⁺/Ca²⁺,the absolute relative deviation（RAD）of R_M-O-O and the binding energy are within 2.2%and 4.3%,respectively,and the linear correlation coefficients of charge distributions from QM and ABEEM/MM rages from 0.98¹.03,the corresponding linear slope is close to 1,and the intercept is close to zero.