Infrared spectra of 5-fluorouracil molecules isolated in inert Ar matrices, and their films on graphene oxide at 6 K

Abstract

The FTIR spectra of 5-fluorouracil (5FU) molecules isolated in low-temperature (T = 6 K) argon matrices were observed in the infrared range of 3800–200 cm−1. The FTIR spectra of graphene oxide (GO) films on a copper mirror at a temperature of 6 K and the spectra of 5FU films grown on GO films were recorded for the first time. Estimates of the 5FU tautomer population using quantum-mechanical methods DFT/B3LYP and MP2, and calculations of the 5FU vibrational spectra using the DFT/B3LYP/6-311++G(df,pd) method with a correction to the calculated frequencies by a third-order polynomial were performed. It is found that the population of the minor 5FU tautomers at an evaporation temperature of 375 K does not exceed 0.1%. In the spectral range of 1900–500 cm−1 ten 5FU combination modes are registered, which are amplified by the Fermi resonance. In the region of fundamental vibrations νCO, triple Fermi resonance is observed. It is demonstrated that low temperatures have little effect on the spectral characteristics of GO films. Furthermore, multiple thermal cycling between 6 and 295 K does not violate the integrity of the GO films and their thermal contact with the copper mirror. The FTIR spectra of 5FU matrix and film samples grown on different substrates are compared. A gain in the absorption band of thin-film 5FU grown on GO, in comparison to samples grown on a Cu substrate, is recorded. It is established that the infrared spectrum changes when the 5FU deposited on GO film is annealed. The relationship between these spectral changes and the polymorphism of the 5FU crystal structure is discussed.

Hydroxypropyl methylcellulose/graphene oxide composite as drug carrier system for 5‐fluorouracil

“…[ 34 ] The spectrum with frequencies less than 1000 cm −1 attributes the absorption bands of stretching vibrations of the pyrimidine ring and planar/nonplanar deformation vibrations of 5‐FU. [ 35,38 ]…”

Interaction of 5‐fluorouracil with β‐cyclodextrin: A density functional theory study with dispersion correction

“…This is in agreement with earlier work on 5FU with four water molecules [ 23 ] and with experimental findings. [ 31,37,65 ] The authors also observed a difference between keto and enol forms with four water molecules of about 30 kJ/mol at the MP2/6‐31+G(d,p) level of theory. Early infrared (IR) studies in the Ar matrix revealed signals from the keto form of 5FU only, [ 37 ] and the potential concentration of minor tautomers was assumed to be below 0.1%.…”

“…Similar conclusion from low‐temperature IR matrix studies were reported recently. [ 65 ] In addition, recent photoluminescence studies also indicate the keto form as the most abundant form. [ 31 ] Thus, on the previously optimized structures of K_5w and K_5m complexes, we performed single‐point calculations, with the original B3LYP functional lacking a dispersion correction term.…”

Spectral and structural features of bio-composite films of graphene oxide and molybdenum disulphide with molecules of 5-bromouracyl and 5-bromo-2’-deoxyuridine

“…Поэтому, изучение взаимодействия галогенпроизводных урацила с наночастицами представляет интерес для создания композитных наноструктур с различными биотехнологическими и биомедицинскими функциями. Исходя из опыта наших предыдущих исследований композитных пленок [9][10][11], в качестве объектов данного исследования были выбраны биокомпозитные пленки: 5BrU/GO, 5BrU/MoS 2 , 5BrdU/GO и 5BrdU/MoS 2 .…”