Vibrational spectroscopic studies on 2′-3′-didehydro-2′-3′-dideoxythymidine using density functional theory method

FTIR and FT-Raman spectra of 2′-3′-didehydro-2′-3′-dideoxythymidine have been recorded and analyzed. The molecular geometry and vibrational frequencies and intensity of the vibrational bands are interpreted with the aid of structure optimization based on density functional theory (DFT) B3LYP method with 6-31G(d,p) and 6-31++G(d,p) basis sets. The results of the optimized molecular structure are presented and compared with the experimental X-ray diffraction data. The theoretical results show that the optimized geometry can well reproduce the crystal structure, and the calculated vibrational frequency values show good agreement with experimental values. A study of the electronic properties, such as HOMO and LUMO energies were performed. Mulliken charges and NBO charges of the title molecule were also calculated and interpreted. Thermogravimetric analysis has been done to study the thermal behavior of 2′-3′-didehydro-2′-3′-dideoxythymidine. The 13C nuclear magnetic resonance (NMR) chemical shift of the molecule are calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results.