Interpretation of electronic spectra of a number of 5-substituted uracils in aqueous solution based on modeling of their H-complexes with water molecules and the orbital approach

Absorption spectra of 5-hydroxymethyluracil, uracil, 5-fluorouracil and 5-bromouracil in a neutral aqueous solution were obtained. The modeling of hydrogen complexes of molecules of the compounds under consideration with water molecules was carried out, and then the absorption spectra in aqueous solution were calculated using the TDDFT B3LYP/6-311+G(d, p) method in combination with the polarizable continuum model. The linear dependence of the energies of electronic transitions obtained from the absorption spectra on the values of the energy gap between the corresponding occupied and vacant molecular orbitals of the calculated hydrogen complexes is shown.