Structures and infrared spectra of 5-chlorouracil molecules in the low-temperature inert Ar, Ne matrices, and composite films with graphene oxide
A.Yu. Ivanov, Yu.V. Rubin, L.F. Belous, and V.A. Karachevtsev
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Nauky Ave., Kharkiv 61103, Ukraine
Received March 2, 2018
The structures and vibrational spectra of biologically active molecules of 5-chlorouracil (5CU) in various states have been studied. In the infrared range 3800–500 cm–1, the IR-Fourier spectra of 5CU molecules isolated in the low-temperature Ar and Ne matrices were obtained. Estimations of the population of 5CU tautomers and calculations of the vibrational spectra by the DFT/B3LYP method with a basis of 6-311++G (df,pd) are performed. In the Ar matrix, 7 Raman modes of 5CU amplified by Fermi resonance were de-tected in the spectral range 1900–500 cm–1. In the region of fundamental vibrations νCO and in the vibration region of the ring, triple Fermi resonances are observed. Thin films of 5CU on the surface of graphene oxide (GO) and 5CU/GO composite films obtained from an aqueous solution were grown and investigated at cryogenic temperatures. It is shown that as the temperature rises from the helium temperature to room temperature, the 5CU film crystallizes on the GO surface. By comparing the spectra of the 5CU films obtained, oscillations are identified, whose bands are most sensitive to changes in the crystal structure of the film. Most of these fundamental modes are associated with vibrations of the NH group. With an increase in the concentration of 5CU in the 5CU/GO composite films, a nonuniform distribution of the 5CU micro-crystals over the sample area is observed.
PACS: 33.15.–e Properties of molecules; PACS: 33.20.Ea Infrared spectra.