Ab initio study, investigation of NMR shielding tensors, NBO and vibrational frequency of catechol thioethers
The electrochemical oxidation of dopamine and 3,4-dihydroxymethamphetamine (HHMA) has been studied in the presence of GSH and cysteine as a nucleophile. In order to determine the optimized geometries, energies, dipole moments, atomic charges, thermochemical analysis and other properties, we performed quantum chemical ab initio and density functional calculations at B3LYP level with 6-31G* basis set. The structural and vibrational properties of 5-S-glutathionyldopamine, 5-S-cysteinyldopamine and 5-S-N-acetylcysteinyldopamine are studied. The chemical shifts of anisotropy and ∆δ are calculated. The gauge-invariant atomic orbital (GIAO) method was employed to calculate isotropic atomic shielding of compounds. These calculations yield molecular geometries in good agreement with available experimental data. The bond lengths, bond angles, dipole moment, electron affinity, ionization potential, electronegativy, absolute hardness, highest occupied molecular orbital (HOMO) and the energy of the lowest unoccupied molecular orbital (LUMO) of the studied compounds were calculated in gas phase and water. NMR analysis of dopamine-o-quinone-glutathione conjugate revealed that the addition of glutathione was at C-5 to form glutathionyl-dopamine.
KEY WORDS: Catechol thioether, Dopamine, NMR, GIAO, B3LYP, NBO
Bull. Chem. Soc. Ethiop. 2010, 24(2), 227-237.