Raman and IR studies and DFT calculations of the vibrational spectra of 2,4-Dithiouracil and its cation and anion.
Raman and FTIR spectra of solid 2,4-Dithiouracil (DTU) at room temperature have been recorded. DFT calculations were carried out to compute the optimized molecular geometries, GAPT charges and fundamental vibrational frequencies along with their corresponding IR intensities, Raman activities and depolarization ratios of the Raman bands for the neutral DTU molecule and its cation (DTU+) and anion (DTU-) using the Gaussian-03 software. Addition of one electron leads to increase in the atomic charges on the sites N1 and N3 and decrease in the atomic charges on the sites S8 and S10. Due to ionization of DTU molecule, the charge at the site C6 decreases in the cationic and anionic radicals of DTU as compared to its neutral species. As a result of anionic radicalization, the C5C6 bond length increases and loses its double bond character while the C4C5 bond length decreases. In the case of the DTU+ ion the IR and Raman band corresponding to the out-of-phase coupled NH stretching mode is strongest amongst the three species. The anionic DTU radical is found to be the most stable. The two NH out-of-plane bending modes are found to originate due to out-of-phase and in-phase coupling of the two NH bonds in the anion and cation contrary to the case of the neutral DTU molecule in which the out-of-plane bending motions of the two NH bonds are not coupled.
Lasers and Spectroscopy Laboratory, Department of Physics, Banaras Hindu University, Varanasi 221005, India.
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Singh
Lasers and Spectroscopy Laboratory, Department of Physics, Banaras Hindu University, Varanasi 221005, India. Electronic address: ray1357@gmail.com.
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Yadav
D000465:Algorithms; D000838:Anions; D002244:Carbon / Q000737:chemistry; D002412:Cations; D006859:Hydrogen / Q000737:chemistry; D006860:Hydrogen Bonding; D007477:Ions; D015394:Molecular Structure; D009584:Nitrogen / Q000737:chemistry; D016011:Normal Distribution; D010100:Oxygen / Q000737:chemistry; D012984:Software; D013055:Spectrophotometry, Infrared; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D013455:Sulfur / Q000737:chemistry; D013889:Thiouracil / Q000031:analogs & derivatives* / Q000737:chemistry; D014732:Vibration
D000838:Anions; D002412:Cations; D007477:Ions; C056582:2,4-dithiouracil; D013889:Thiouracil; D013455:Sulfur; D002244:Carbon; D006859:Hydrogen; D009584:Nitrogen; D010100:Oxygen
2,4-Dithiouracil and its cation and anion; DFT studies; FTIR and Raman spectra; GAPT charges; Optimized molecular geometries; Vibrational characteristics