| Full text | |
| Author(s): |
Paschoal, Vitor Hugo
;
Ribeiro, Mauro C. C.
Total Authors: 2
|
| Document type: | Journal article |
| Source: | Physical Chemistry Chemical Physics; v. 25, n. 39, p. 11-pg., 2023-10-11. |
| Abstract | |
Protic ionic liquids (PILs) typically show a complex band shape in their infrared (IR) spectra in the high-frequency range due to the hydrogen stretching vibrations of functional groups forming rather strong hydrogen bonds (H-bonds). In the low-frequency range, the intermolecular stretching mode of the H-bond leaves a mark in the far-IR spectrum of PILs. In this study, the IR spectrum of the PIL 2-hydroxyethylammonium formate, [HOCH2CH2NH3][HCOO], is investigated in order to identify the different modes that contribute to the high-frequency band shape, i.e. the cation nu(NH), nu(OH), and nu(CH) modes, and the anion nu(CH) mode, as well as the intermolecular mode of the strongest H-bond in the far-IR spectrum. The assignment is validated by quantum chemistry calculations of clusters at the density functional theory (DFT) level for four ionic pairs and by ab initio molecular dynamics (AIMD) simulations of ten ionic pairs. There is good agreement between the vibrational frequencies obtained from DFT and AIMD simulations for both the high- and low-frequency ranges. Based on the calculations, the strong H-bond interaction between the cation -NH3 group and [HCOO](-) gives a broad band envelope associated with the nu(NH) mode in the high-frequency range of the IR spectrum on which there are narrower peaks corresponding to the nu(OH) and nu(CH) modes. In the far-IR (FIR) spectrum, the anions' rattling motion gives a broad feature with a maximum at 160 cm(-1), while the H-bond ' s intermolecular NH & ctdot;O stretching mode appears as a peak at 255 cm(-1). (AU) | |
| FAPESP's process: | 16/21070-5 - Vibrational spectroscopy with spatial resolution |
| Grantee: | Mauro Carlos Costa Ribeiro |
| Support Opportunities: | Research Projects - Thematic Grants |
| FAPESP's process: | 19/00207-0 - Density functional theory applyed to vibrational dynamics of crystals of ionic systems. |
| Grantee: | Vitor Hugo Paschoal |
| Support Opportunities: | Scholarships in Brazil - Post-Doctoral |