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Ionic Liquids: Not only Structurally but also Dynamically Heterogeneous
Author(s) -
Zheng ZhuanPing,
Fan WenHui,
Roy Soham,
Mazur Kamila,
Nazet Andreas,
Buchner Richard,
Bonn Mischa,
Hunger Johannes
Publication year - 2015
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201409136
Subject(s) - ionic liquid , chemical physics , ionic bonding , relaxation (psychology) , alkyl , chemistry , molecular dynamics , femtosecond , ion , computational chemistry , organic chemistry , physics , social psychology , psychology , laser , optics , catalysis
In recent years, the complex and heterogeneous structure of ionic liquids has been demonstrated; however, the consequences on the dynamics have remained elusive. Here, we use femtosecond IR spectroscopy to elucidate the local structural dynamics in protic alkylammonium‐based ionic liquids. The structural relaxation after an ultrafast temperature increase, following vibrational excitation and subsequent relaxation of the N‐D (or N‐H) stretching vibration, is found to vary substantially between the ionic and hydrophobic subdomains. The dynamics in the ionic domains are virtually unaffected by the alkyl chain length and is, therefore, decoupled from viscosity. Equilibration within the hydrophobic subdomains, as evident from the dynamics of the C‐H stretching vibration, is faster than that in the ionic domains and shows a remarkably low thermal activation.