Infrared Spectra Of Liquids Research Articles

Computationally assisted vibrational spectroscopy of nucleic acid bases. 2. Thymine

As in the case of cytosine [Phys. Chem. Chem. Phys. 2023, 25, 24121–24128], Raman and infrared (IR) spectra of aqueous thymine and its N-deuterated derivative, thymine-d2 have been computationally reproduced and interpreted with the use of the recently developed efficient protocol to explicit quantum mechanical modeling of structure and IR spectra of liquids and solutions [J. Phys. Chem. B, 2020, 124, 6664–6670]. A cluster model of a solute surrounded by 30 water molecules is shown to be sufficient to reproduce experimental vibrational frequencies and relative Raman intensities with the use of B3LYP-D3/def2-TZVP or B3LYP-D3/aug-cc-pVDZ simulations. Analogous PBE-D3 computations provided a less good, but still reasonably accurate, modeling of Raman spectra. It is shown that strong changes of frequencies and relative intensities of the Raman bands of thymine, caused by its hydration, can be interpreted mainly as a result of hydrogen bonding with 6 nearest water molecules. Non-negligible improvement of the quality of simulations for larger clusters comprising water molecules that do not have direct contacts with the solute, suggests that spectroscopic effects of hydration should be ascribed to the joined action of solute–solvent and solvent–solvent interactions. Nevertheless, the moderate number of water molecules required for successful simulations of the Raman spectra of aqueous thymine, suggests that the vibrational modes and derivatives of the polarizability of the solute are mainly locally influenced, while the effect of bulk water is rather modest.

Eine Infrarot-Küvette für Substanzen, die nur bei tiefer Temperatur beständig sind

In using the new infra-red cell it is possible to take infra-red spectra of liquids or solids at a constant low temperature in the range of −160°C to room temperature. The substance to be investigated can be filled in as a liquid or in solution at low temperatures without any heating up during the whole procedure of preparation, filling and recording of the infra-red spectrum.

The Infra-Red Spectra of Liquid and Solid Methane

The Infra-Red Spectra of Liquid and Solid Methane