Vibrational spectra of 1-methylthyminate complexes with mercury(II) and potassium and ab initio calculations of the 1-MeT anion

The FT-Raman and FT-infrared spectra of bis(1-methylthyminato)mercury(II), Hg(1-MeT)2, and potassium 1-methylthyminate, K(1-MeT), are reported. The molecular structure, harmonic vibrational frequencies, infrared intensities and Raman scattering activities of the N3deprotonated 1-MeT anion have been calculated at the HF/6-31++G** and MP2/D95V** levels of theory. A rigorous normal coordinate analysis of the 1-MeT anion has been made. The ab initio predicted frequencies and intensity patterns of the IR and Raman bands as well as the calculated potential energy distribution (PED) have proved to be of great help in assigning the spectra of the title compounds. It is concluded that the potassium cation binds to the oxygen atom of the N3-deprotonated ligand in K(1-MeT). It also follows that the exocyclic C=O bonds in the N3-coordinated mercury(II) complex, Hg(1-MeT)2, are more ionic than those in the neutral 1-methylthymine.