Structures and Electronic Properties of Lithium Chelate-Based Ionic Liquids

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• 作者：Dawei Si ; Kexian Chen ; Jia Yao ; Haoran Li
• 刊名：Journal of Physical Chemistry B
• 出版年：2016
• 出版时间：April 28, 2016
• 年：2016
• 卷：120
• 期：16
• 页码：3904-3913
• 全文大小：466K
• 年卷期：0
• ISSN：1520-5207

文摘

The conformations, electronic properties, and interaction energies of four chelate-based ionic liquids [Li(EA)][Tf₂N], [Li(HDA)][Tf₂N], [Li(DEA)][Tf₂N], and [Li(DOBA)][Tf₂N] have been theoretically explored. The reliability of the located conformers has been confirmed via the comparison between the simulated and experimental infrared spectra. Our results show that the N–Li and O–Li coordinate bonds in cation are elongated as the numbers of coordinate heteroatoms of alkanolamine ligands to Li⁺ increased. Also the binding energies between Li⁺ and ligands are increased and the interaction energies between cations and Tf₂N anion are decreased. The cation–anion interaction energies follow the order of [Li(DOBA)][Tf₂N] < [Li(HDA)][Tf₂N] < [Li(DEA)][Tf₂N] < [Li(EA)][Tf₂N], which fall within the energetic ranges of conventional ionic liquids. Interestingly, the strongest stabilization orbital interactions in these ionic liquids and their cations revealed by the natural bond orbital analysis lie in the interaction between the lone pair (LP) of the coordinate heteroatoms in ligands or anion as donors and the vacant valence shell nonbonding orbital (LP*) of Li⁺ as acceptors, which are very different from that of conventional ionic liquids. Moreover, the charges transferred from cations to anion are quite similar, and the charge of Li⁺ is proposed for possibly predicting the order of the interaction energies of ionic liquids in series. The present study allows for the deeper understanding the differences between chelate-based ionic liquids and conventional ionic liquids.