The structure of [Ru(bpy)(CN)4]-2 and its solvent shell in aqueous solution has been investigated by the X-ray diffraction technique. The characteristic bond lengths of the complex obtained by this method are in good agreement with those determined by a single-crystal X-ray study. The number of solvent molecules of the hydration shell has been determined. Three water molecules are arranged near to each cyanide ligand. The average distance between the nitrogen atoms of the cyanides and the oxygen atoms of these solvent molecules is found to be 3.2 Å. To examine this specific solvent-solute interaction, DFT calculations were performed on the gas phase complex and on its partially hydrated cluster models [Ru(bpy)(CN)4]2- · (H2O)n (n = 4, 8). These calculations confirmed the relatively strong CN⋯H-OH hydrogen bonds. It has also been demonstrated that the hydrogen bond is notably weaker in the triplet excited state than in the ground state of the complex. The lengthening of the N⋯H bonds due to the formation of the triplet excited complex is about 0.05 Å, and an appreciable influence on the second hydration shell is also demonstrated by the increase of the related O⋯H bond, which is at least 0.02 Å longer in the excited state.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry