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On the components of the dielectric constants of ionic liquids: ionic polarization?
MedLine Citation:
PMID:  19325978     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Abstract/OtherAbstract:
According to dielectric spectroscopy measurements, ionic liquids (ILs) have rather modest dielectric constants that reflect contributions from distortion and electronic polarization caused by the molecular polarizability as well as the orientation polarization caused by the permanent dipole moment of the ions. To understand the relative importance of these various contributions, the electronic polarizabilities of 27 routinely used ionic liquid ions of different symmetry and size were calculated using ab initio-based methods such as HF and MP2. Using the Clausius-Mossotti equation, these polarizabilities were then used to obtain the electronic polarization contribution (epsilon(op)) to the dielectric constants of six ionic liquids, [C(2)mim][BF(4)], [C(2)mpyr][N(CN)(2)], [C(2)mim][CF(3)SO(3)], [EtNH(3)][NO(3)], [C(2)mim][NTf(2)] and [C(2)mim][EtSO(4)]. Theoretical epsilon(op) values were compared to experimental refractive indices of these ionic liquids as well as to those of traditional molecular solvents such as water, tetrahydrofuran (THF), dimethylsulfoxide (DMSO) and formamide. The dipole moments of the ions were also calculated, and from these it is shown that the molecular reorientation component of the dielectric constants of the ionic liquids consisting of ions with small or negligible dipole moments is quite small. Thus it is concluded that a contribution from a form of "ionic polarization" must be present.
Authors:
Ekaterina I Izgorodina; Maria Forsyth; Douglas R Macfarlane
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2009-02-11
Journal Detail:
Title:  Physical chemistry chemical physics : PCCP     Volume:  11     ISSN:  1463-9076     ISO Abbreviation:  Phys Chem Chem Phys     Publication Date:  2009 Apr 
Date Detail:
Created Date:  2009-03-27     Completed Date:  2009-06-10     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100888160     Medline TA:  Phys Chem Chem Phys     Country:  England    
Other Details:
Languages:  eng     Pagination:  2452-8     Citation Subset:  -    
Affiliation:
School of Chemistry, Monash University, Clayton, Vic 3800 Melbourne, Australia. katya.izgorodina@sci.monash.edu.au
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