Конформеры нуклеозидов в низкотемпературных матрицах аргона: ИК фурье-спектроскопия изолированных молекул тимидина, дейтеротимидина и квантово-механические расчеты

The conformational equilibrium of thymidine and deuterothymidine molecules in low-temperature Ar matrices was investigated with using low-temperature Fourier transform infrared spectroscopy of the matrix isolation and quantum chemical calculations by the DFT/B3LYP and MP2 methods. It was established that two anti-conformers ta2_0, ta3_0 with different structures of the sugar ring: C2′-endo and C3′-endo dominate in low-temperature matrices. In the gas phase, each of these conformers has several low-barrier satellites that can be completely transformed into more stable structures when molecules are frozen in matrices. The main synconformer ts2_0 is stabilized by the intramolecular hydrogen bond O5′H∙∙∙O2, and the dominant conformation of the deoxyribose ring is C2′-endo. The significant loss in the population of ts2_0 structure to the anti-conformers ta2_0, ta3_0 can be explained by a smaller occupation of low-barrier conformer satellites. It is shown that the absorption band of the valence vibration νN3D may be split by the Fermi resonance.