RESUMEN

The vertical excitation and emission energies of the cytosine oxo-amino form were calculated at the TD DFT level of theory with several functionals, basis sets, and solvents with different polarity (PCM). They were compared with the experimental UV absorption and fluorescence maxima, revealing that the minimal deviation of the vertical excitation energies from the of UV absorption maxima can be achieved when the hybrid functional B3LYP is applied within the calculations. Regular correlations like curves with saturation between the vertical excitation/emission energies and the dielectric constants were registered. The relaxation of the 1ππ* excited state through an ethylene-like conical intersection S0/S1 should occur through decrease of the decay rate (commented qualitatively here) with the rise of the solvent polarity.

Asunto(s)

Citosina , Teoría Funcional de la Densidad , Fluorescencia , Solventes

RESUMEN

We performed a theoretical and experimental study of the (photo)stability of 3,5-dinitrocatechol (DNC) and its complexes with W(VI) and V(V). The investigation showed that irradiation of DNC is accompanied by a parallel proton migration from the hydroxy group to the neighboring NO2 group, which results in a large Stokes shift of the absorption and emission bands. It was found that W(VI) forms a more stable 1:2 complex than V(V). The complex is stable even under UV irradiation. The most stable W(VI)(DNC)2 conformer is comprised of two mutually perpendicular DNC molecules as ligands.