2D Raman-THz spectroscopy of binary CHBr3-MeOH solvent mixture

TL;DR

This study employs hybrid 2D Raman-THz spectroscopy to investigate solvent interactions in a CHBr3-MeOH mixture, revealing coupling of intramolecular and intermolecular modes and the formation of hydrogen bonds at specific compositions.

Contribution

It introduces the use of 2D Raman-THz spectroscopy to analyze solvent interactions and hydrogen bonding in binary mixtures, providing new insights into low-frequency mode couplings.

Findings

Detection of a new cross peak at 0.3 molar fraction indicating hydrogen bonding.

Observation of coupling between intramolecular bending and collective modes.

Support from measurements on related solvent systems and 1D absorption data.

Abstract

Hybrid two-dimensional (2D) Raman-terahertz spectroscopy is used to measure the interactions between two solvents pair in the binary CHBr3-MeOH mixture in the frequency range of 1-7 THz. Changes in the cross peak signature are monitored, originating from the coupling of an intramolecular bending mode of CHBr3 to the collective intermolecular degrees of freedom of the mixture. The appearance of a new cross peak in the 2D spectrum measured for solvent mixture with MeOH molar fraction of 0.3 indicates a coupling to a new set of low-frequency modes formed due to the hydrogen bond interactions between the two solvents. This interpretation is supported by the measurement of the CHBr3-CS2 binary solvent mixture as well as by 1D absorption measurements of neat MeOH.