How does the ionic liquid organizational landscape change when nonpolar cationic alkyl groups are replaced by polar isoelectronic diethers?

Hemant K Kashyap; Cherry S Santos; Ryan P Daly; Jeevapani J Hettige; N Sanjeeva Murthy; Hideaki Shirota; Edward W Castner Jr; Claudio J Margulis

doi:10.1021/jp311032p

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How does the ionic liquid organizational landscape change when nonpolar cationic alkyl groups are replaced by polar isoelectronic diethers?

Journal article

Peer reviewed

How does the ionic liquid organizational landscape change when nonpolar cationic alkyl groups are replaced by polar isoelectronic diethers?

Hemant K Kashyap, Cherry S Santos, Ryan P Daly, Jeevapani J Hettige, N Sanjeeva Murthy, Hideaki Shirota, Edward W Castner Jr and Claudio J Margulis

The journal of physical chemistry. B, Vol.117(4), pp.1130-1135

01/31/2013

DOI: 10.1021/jp311032p

PMID: 23259707

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Abstract

X-ray scattering experiments and molecular dynamics simulations have been performed to investigate the structure of four room temperature ionic liquids (ILs) comprising the bis(trifluoromethylsulfonyl)amide (NTf(2)(-)) anion paired with the triethyloctylammonium (N(2228)(+)) and triethyloctylphosphonium (P(2228)(+)) cations and their isoelectronic diether analogs, the (2-ethoxyethoxy)ethyltriethylammonium (N(222(2O2O2))(+)) and (2-ethoxyethoxy)ethyltriethylphosphonium (P(222(2O2O2))(+)) cations. Agreement between simulations and experiments is good and permits a clear interpretation of the important topological differences between these systems. The first sharp diffraction peak (or prepeak) in the structure function S(q) that is present in the case of the liquids containing the alkyl-substituted cations is absent in the case of the diether substituted analogs. Using different theoretical partitioning schemes for the X-ray structure function, we show that the prepeak present in the alkyl-substituted ILs arises from polarity alternations between charged groups and nonpolar alkyl tails. In the case of the diether substituted ILs, we find considerable curling of tails. Anions can be found with high probability in two different environments: close to the cationic nitrogen (phosphorus) and also close to the two ether groups. For the two diether systems, anions are found in locations from which they are excluded in the alkyl-substituted systems. This removes the longer range (polar/nonpolar) pattern of alternation that gives rise to the prepeak in alkyl-substituted systems.

Cations - chemistry

X-Rays

Models, Molecular

Ethers - chemistry

Scattering, Radiation

Ionic Liquids - chemistry

Alkanes - chemistry

Molecular Dynamics Simulation

Details

Title: Subtitle: How does the ionic liquid organizational landscape change when nonpolar cationic alkyl groups are replaced by polar isoelectronic diethers?
Creators: Hemant K Kashyap - Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, USA
Cherry S Santos
Ryan P Daly
Jeevapani J Hettige
N Sanjeeva Murthy
Hideaki Shirota
Edward W Castner Jr
Claudio J Margulis
Resource Type: Journal article
Publication Details: The journal of physical chemistry. B, Vol.117(4), pp.1130-1135
DOI: 10.1021/jp311032p
PMID: 23259707
NLM abbreviation: J Phys Chem B
ISSN: 1520-6106
eISSN: 1520-5207
Publisher: American Chemical Society; United States
Language: English
Date published: 01/31/2013
Academic Unit: Chemistry
Record Identifier: 9983985851302771

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