Identification of multiple conformers of the ionic liquid [emim][tf2n] in the gas phase using IR/UV action spectroscopy

Abstract

In this study we investigate the effect of deuteration and molecular beam temperature on the hydrogen bond in the ionic liquid [emim][tf2n]. Using IR/UV double resonance spectroscopy, we probe the microscopic structure of the [emim][tf2n] ion pair and its mono-deuterated, [emim-d₁][tf2n], analog. Comparisons of the infrared absorption frequencies between these two species show that there are multiple conformers of the ion pair present in the gas phase and trapped through the molecular beam cooling process. Furthermore, each conformer has a characteristic red shift in the frequency of its C2–H group that reveals the variation in strength of a hydrogen bond between the cation and anion.