Ground- and excited-state stability of the conformers of 3,5-dinitrocatechol and its complexes with W(VI) and V(V): combined theoretical and experimental study.

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.