Ru–Zn Heteropolynuclear Complexes Containing a Dinucleating Bridging Ligand: Synthesis, Structure, and Isomerism

Mononuclear complexes in- and out-[Ru­(Cl)­(trpy)­(Hbpp)]+ (in-0, out-0; Hbpp is 2,2′-(1H-pyrazole-3,5-diyl)­dipyridine and trpy is 2,2′:6′,2″-terpyridine) are used as starting materials for preparation of Ru–Zn heterodinuclear out-{[Ru­(Cl)­(trpy)]­[ZnCl2]­(μ-bpp)} (out-2) and heterotrinuclear in,in- and out,out-{[Ru­(Cl)­(trpy)]2(μ-[Zn­(bpp)2])}2+ (in-3, out-3) constitutional isomers. Further substitution of the Cl ligand from the former complexes leads to Ru–aqua out,out-{[Ru­(trpy)­(H2O)]2(μ-[Zn­(bpp)2])}4+ (out-4) and the oxo-bridged Ru–O–Ru complex in,in-{[RuIII(trpy)]2(μ-[Zn­(bpp)2(H2O)]­μ-(O)}4+ (in-5). All complexes are thoroughly characterized by the usual analytical techniques as well as by spectroscopy by means of UV–vis, MS, and when diamagnetic NMR. CV and DPV are used to extract electrochemical information and monocrystal X-ray diffraction to characterize complexes out-2, in-3, out-3, and in-5 in the solid state. Complex out-3 photochemically isomerizes toward in-3, as can be observed by NMR spectroscopy and rationalized by density functional theory based calculations.