Direct calculation of the temperature dependence of 2D-IR spectra: Urea in water
Ashley K Borkowski1, N Ian Campbell1, Ward H Thompson1
1Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, USA.
Abstract:
A method for directly calculating the temperature derivative of two-dimensional infrared (2D-IR) spectra from simulations at a single temperature is presented. The approach is demonstrated by application to the OD stretching spectrum of isotopically dilute aqueous (HOD in H2O) solutions of urea as a function of concentration. Urea is an important osmolyte because of its ability to denature proteins, which has motivated significant interest in its effect on the structure and dynamics of water. The present results show that the temperature dependence of both the linear IR and 2D-IR spectra, which report on the underlying energetic driving forces, is more sensitive to urea concentration than the spectra themselves. Additional physical insight is provided by calculation of the contributions to the temperature derivative from different interactions, e.g., water-water, water-urea, and urea-urea, present in the system. Finally, it is demonstrated how 2D-IR spectra at other temperatures can be obtained from only room temperature simulations.
Related Concept Videos
IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations
IR and UV–Vis Spectroscopy of Aldehydes and Ketones
IR Frequency Region: X–H Stretching
NMR Spectroscopy Of Amines
IR Spectrum Peak Broadening: Hydrogen Bonding
However, the extent of hydrogen bonding influences the observed stretching frequency and band broadening. Intermolecular or intramolecular...
IR and UV–Vis Spectroscopy of Carboxylic Acids
However, the stretching absorptions for the C=O bond vary depending on the structure of carboxylic acids. The C=O bond of the free carboxylic acids shows a higher stretching frequency, 1760 cm−1, while H-bonded carboxylic acids (dimers) exhibit stretching absorptions at a lower frequency,...


