Dinuclear nitrido-bridged ruthenium complexes bearing diimine ligands

Reactions of K₃[Ru₂NCl₈(H₂O)₂] with 2,2'-bipyridine (bpy), 4,4'-dimethyl-2,2'-bipyridine (dmbpy), and 4,4'-dimethoxy-2,2'-bipyridine (dmobpy) yielded the nitrido-bridged dinuclear complexes [Ru₂N(L)₂Cl₅(DMF)] where L = bpy (1), dmbpy (2), and dmobpy (3). The crystal structures of these complexes reveal a linear Ru-N-Ru moiety with each ruthenium center bearing a bidentate diimine ligand. The complexes were further characterized by NMR, IR, and UV-vis spectroscopic methods and cyclic voltammetry. Because the compounds bear some structural similarities with the mitochondrial calcium uptake inhibitor Ru360, the ability of these complexes to act in this capacity was evaluated. The results demonstrate that 1-3 all fail to block mitochondrial calcium uptake, revealing new facets of the structure-activity relationships for ruthenium-based mitochondrial calcium uptake inhibitors.