Nuclear Magnetic Resonance Studies on the Structure of Ruthenium(II) Complexes of Di-2-pyridylamine in DMSO Solution

The complete assignments of the 1H and 13C NMR spectra of [Ru(bpy)n(Hdpa)3−n]2+ (n = 0—2) have been carried out on the basis of proton–proton coupling constants, H–H COSY, C–H COSY, and the aromatic ring-current effects of the ligand. The observed aromatic ring-current shifts of the assigned 1H NMR signals were compared with the calculated ones by using a current-loop model. The flapping of the Hdpa ligands showed that the structures of [Ru(bpy)2(Hdpa)]2+, [Ru(bpy)(Hdpa)2]2+, and [Ru(Hdpa)3]2+ in solution have apparent C2, C2, and D3 symmetries, respectively.