论文部分内容阅读
The Hartree-Fock and DFT/B3LYP methods have been employed to investigate the electronic structures of 1-ethy1-3-methyl-imidazolium cation(EMIM~+),BF_4~-,PF_6~-,EMIM~+-BF_4~-,and EMIM~+-PF_6~- using the Gaussian-94 soft-package at 6-31+G(d,p)basis set level for hydrogen,carbon,nitrogen,boron, phosphorus,and fluorine atoms.Comparison of the electronic structures of the lowest energy of EMIM~+- BF_4~- and EMIM~+-PF_6~- pairs,and single EMIM~+,BF_4~- and PF_6~- showed that the optimized EMIM~+-BF_4~- and EMIM~+-PF_6~- pair conformers were BF_4~- and PF_6~- outside the 5-ring plane between the ethyl group and the methyl group.The cohesion of C—H…F hydrogen bond between cation and anion is reinforced by charge assistance.The interaction energy between EMIM~+ and PF_6~- is 328.8 kJ/mol at the B3LYP level and 326.6 kJ/mol at the Hartree-Fock level,whereas that between EMIM~+ and BF_4~- is 353.5 kJ/mol at the B3LYP level and 350.5 kJ/mol at the Hartree-Fock level.The low energy interactions caused by bulky asymmetric EMIM~+,and charge dispersion of cation and anion give rise to the low melting point of ionic liquid EMIM~+-BF_4~- and EMIM~+-PF_6~-.The two hydrogen bonding models of single hydrogen bond formation,and the hydrogen transfer between C_2 in EMIM~+ and F in BF_4~- or PF_6~- were principally depicted.
The Hartree-Fock and DFT / B3LYP methods have been employed to investigate the electronic structures of 1-ethy1-3-methyl-imidazolium cation (EMIM ~ +), BF4 ~ -, PF6 ~, EMIM ~ + -BF4 ~ and EMIM ~ + -PF_6 ~ - using the Gaussian-94 soft-package at 6-31 + G (d, p) basis set level for hydrogen, carbon, nitrogen, boron, phosphorus, and fluorine atoms. Comparison of the electronic structures the lowest energy of EMIM ~ + - BF_4 ~ - and EMIM ~ + -PF_6 ~ - pairs, and single EMIM ~ +, BF_4 ~ - and PF_6 ~ - showed that the optimized EMIM ~ + -BF_4 ~ - and EMIM ~ +, - PF_6 ~ - pair conformers were BF_4 ~ - and PF_6 ~ - outside the 5-ring plane between the ethyl group and the methyl group. The cohesion of C-H ... F hydrogen bond between cation and anion is reinforced by charge assistance. The interaction energy between EMIM ~ + and PF_6 ~ is 328.8 kJ / mol at the B3LYP level and 326.6 kJ / mol at the Hartree-Fock level, but that between EMIM ~ + and BF_4 ~ is 353.5 kJ / mol at the B3LYP level and 350.5 kJ / mol at the Hartree-Fock level. The low energy interactions caused by bulky asymmetric EMIM ~ +, and charge dispersion of cation and anion give rise to the low melting point of ionic liquid EMIM ~ + -BF_4 ~ - and EMIM ~ + -PF_6 ~ -The two hydrogen bonding models of single hydrogen bond formation, and the hydrogen transfer between C_2 in EMIM ~ + and F in BF_4 ~ - or PF_6 ~ were were principally depicted.