Modeling the Structures and Electronic Properties of Uracil and Thymine in Gas Phase and Water

The molecular geometries and electronic properties of Uracil and Thymine are studied at the Restricted Hatree-Fock (RHF) and Density Functional Theory (DFT) levels of theory in gas phase and water. The optimized structures, dipole moments, total energies, charge transfer, quadrupole moments and other electronic properties of the two molecules were computed in gas and water. The two molecules showed higher polarity, stability and band gap in water. The average bond lengths of Thymine are greater than those of Uracil in gas. Thymine has significantly lower bond lengths than Uracil in solution. The average bond lengths of C-C and N-H are respectively the longest and shortest. Thymine molecule has lower total energies compared to Uracil at both levels of theory and in both media. The polarity of both molecules increases in solution. HOMO and LUMO energy values decrease slightly in solution for both molecules at both levels of theory. The Ionization Potential (IP) and Electron Affinity (EA) decreases for both molecules in solution. The chemical potential and electrophilicity of both molecules increase in solution. The chemical hardness of Uracil increases slightly in solution while that of Thymine decreases slightly in solution.