New procedures for the synthesis of mixed-metal and/or mixed-ligand ruthenium(II) and osmium(II) polypyridine supramolecules and the use of these procedures in the preparation of hexanuclear species

The use of a protection/deprotection procedure within the "complexes-as-ligands/complexes-as-metals" strategy for the synthesis of oligonuclear Ru(II) and Os(II) polypyridine complexes is reported. The preparation of the monochelating cationic ligand 2-[2-(1-methylpyridiniumyl)]-3-(2-pyridyl)pyrazine [(2,3-Medpp)+, 1] is described, along with the synthesis of the trinuclear building blocks {(2,3-Medpp)Ru[(mu-2,5-dpp)Ru(bPY)2]2}(PF6)7 (2), {-(2,3-dpp)Ru[(mu-2,5-dpp)Ru(bpy)2]2}(PF6)6 (3), {Ru[(mu-2,3-dpp)Ru(biq)2]2Cl}(PF6)4 (4), and (Ru[(mu-2,3-dpp) Os(bpY)2]2Cl2}(PF6)4 (5) [dpp = bis(2-pyridyl)pyrazine; bpy = 2,2'-bipyridine; biq = 2,2'-biquinoline]. The use of the above building blocks is illustrated in the preparation of four new hexanuclear complexes of general formula {[ML2(mu-2,m-dpp)]2Ru(mu-2,3-dpp)Ru[(mu-2,n-dpp)M'L'2]2}(PF6)12 (6, M = M' = Ru, L = L' = biq, m = n = 3; 7, M = M' = Ru, L = bpy, L' = biq, m = 5, n = 3; 8, M = M' = Os, L = L' = bpy, m = n = 3; 9, M = Ru, M' = Os, L = L' = bpy, m = 5, n = 3). The new synthetic procedure is discussed with reference to the design of "made-to-order" luminescent and redox-reactive compounds of unusual composition and topologies.