Reply to ‘Comment on “Understanding the infrared spectrum of the protic ionic liquid [DEMA][TfO] by atomistic simulations”’ by J. Joo and A. L. L. East, Phys. Chem. Chem. Phys., 2026, 28, DOI: 10.1039/D5CP02379C

Abstract

Joo and East have recently published a Comment on our article (F. Parisi et al., Phys. Chem. Chem. Phys., 2024, 26, 28037, https://doi.org/10.1039/D3CP06047K). The Comment is based on the wrong assumption that we misassigned the infrared spectrum of liquid diethylmethylammonium triflate [DEMA][TfO]. The authors incorrectly claim that our hypothesis was that the two bands are due to the NH stretch mode in two different ion-pair structural types. We clarify here that our original analysis did not invoke two separate, static ion-pair structures, but rather a continuum of dynamically evolving hydrogen-bonding environments that naturally produce a broadened, bimodal band shape. The results presented in our paper are aligned with the ones presented in the Comment. The Comment brings up the concept of Fermi resonance, which indeed gives a plausible explanation of the features seen in the experimental absorption spectra.