Molecular mobility in several imidazolium‐based ionic liquids according to data of <scp>¹H</scp> and <scp>¹³C NMR</scp> relaxation

Abstract

Temperature dependences are compared for 1 H and 13 C NMR 1/T 1 curves relaxation rates in three imidazolium‐based ionic liquids (ILs), namely, in [bmim]PF 6 , [bmim]BF 4 , and [emim]CH 3 COO. 13 C curves show alike behavior for all three ILs and follow a well‐known Bloembergen‐Pound‐Purcell (BPP) equation. On the contrary, an essential part of 1 H curves differ strongly from corresponding 13 C ones and also have different shapes for different ILs. For the first time, we have detected the specific, two‐maximum shape of 1 H relaxation curve for hydrogen atom of C(2)H group of the [emim]CH 3 COO. Assuming that this maximum reflects the correlated rotation of several adjoining ion pairs, we have tried to destroy this rotation by addition of glycerol to the [emim]CH 3 COO. The second, high‐temperature maximum has disappeared in the [emim]CH 3 COO–glycerol mixture, and this fact confirms our assumption. Copyright © 2017 John Wiley &amp; Sons, Ltd.