Gas phase model of an ionic liquid: Semi-empirical and ab initio bonding and molecular structure
Meng, Zhizhong Dölle, A. Carper, W. Robert
Meng, Zhizhong
Dölle, A.
Carper, W. Robert
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2002-05-17
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Article
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Ab initio ion pairs,Bminm <sup>+</sup>PF<sub>6</sub><sup>-</sup>,Hydrogen bonding,Ionic liquids,Semi-empirical ion pairs
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Z. Meng, A. Dölle, W. Robert Carper,Gas phase model of an ionic liquid: semi-empirical and ab initio bonding and molecular structure,Journal of Molecular Structure: THEOCHEM,Volume 585, Issues 1–3,2002,Pages 119-128,ISSN 0166-1280https://doi.org/10.1016/S0166-1280(02)00056-8..
Abstract
Semi-empirical (AM1 and PM3) and ab initio structures of the gas phase ion pair, bmim + (1-butyl-3-methyl imidazolium)-PF6-, have been calculated. The ab initio calculations include fully optimized structures at the RHF/3-21G(*), RHF/6-31G*, RHF/6-31G**, MP2/6-31G*, B3LYP/6-31G* and B3LYP/6-31G** levels. Semi-empirical structures (AM1 and PM3) are similar to those obtained from ab initio methods. The non-bonded interactions in these ion pairs are of the C-H···X type (C-H···F hydrogen bonds) and exist between F's on PF6- and (a) the imidazolium ring N-H, (b) the methyl group H adjacent to the ring and (c) H's on the butyl (bmim+) side chain. The ab initio ion pair structures contain hydrogen bonds that shorten with increasing basis set complexity. The movement of the bmim+ imidazolium ring C2-H along the proton transfer coordinate towards PF6- produces similar anharmonic functions for the RHF/6-31G*//6-31G**, MP2/6-31G*//6-31G**, RHF/6-31G**/6-31 + G(d,p)//6-31G**, MP2/6-31G**/6-31 + G(d, p)//6-31G**, B3LYP/6-31G*//6-31G** and B3LYP/6-31G**/6-31 + G(d, p)//6-31G** levels. The existence of anharmonic functions that describe the proton transfer coordinate is consistent with the Del Bene model of hydrogen bonding. © 2002 Elsevier Science B.V. All rights reserved.
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Elsevier
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Computational and Theoretical Chemistry
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01661280