Validation of Structural Grounds for Anomalous Molecular Mobility in Ionic Liquid Glasses.

Mikhail Yu Ivanov,Nicolay Yu Adonin,Olga D Bakulina,Alexey S Kiryutin,Sergey A Prikhod'Ko,Matvey V Fedin

doi:10.3390/molecules26195828

Mikhail Yu Ivanov, Nicolay Yu Adonin + Show 4 more

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https://doi.org/10.3390/molecules26195828

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Abstract

Ionic liquid (IL) glasses have recently drawn much interest as unusual media with unique physicochemical properties. In particular, anomalous suppression of molecular mobility in imidazolium IL glasses vs. increasing temperature was evidenced by pulse Electron Paramagnetic Resonance (EPR) spectroscopy. Although such behavior has been proven to originate from dynamics of alkyl chains of IL cations, the role of electron spin relaxation induced by surrounding protons still remains unclear. In this work we synthesized two deuterated imidazolium-based ILs to reduce electron–nuclear couplings between radical probe and alkyl chains of IL, and investigated molecular mobility in these glasses. The obtained trends were found closely similar for deuterated and protonated analogs, thus excluding the relaxation-induced artifacts and reliably demonstrating structural grounds of the observed anomalies in heterogeneous IL glasses.

Highlights

Ionic liquids (ILs) exhibit a number of unusual and advanced properties [1,2,3], making them prospective media for various chemical processes in many fields of modern science and technology [4,5,6,7,8]
Anomalous suppression of molecular mobility in imidazolium IL glasses vs. increasing temperature was evidenced by pulse Electron Paramagnetic Resonance (EPR) spectroscopy
Scheme 1 shows the structures of ILs in deuterated and protonated forms studied in this work, along with the structure of nitroxide radical used as a spin probe

Summary

Introduction

Ionic liquids (ILs) exhibit a number of unusual and advanced properties [1,2,3], making them prospective media for various chemical processes in many fields of modern science and technology [4,5,6,7,8]. In this work we synthesized two deuterated imidazolium-based ILs to reduce electron–nuclear couplings between radical probe and alkyl chains of IL, and investigated molecular mobility in these glasses.

Results

Conclusion