Assembly, characterization, and electrochemical properties of immobilized metal bipyridyl complexes on silicon(111) surfaces

A route to bipyridine-functionalized silicon(111) surfaces has been developed which gave submonolayer surface coverage of immobilized 4-vinyl-2,2'-bipyridyl (vbpy). The remaining atop sites of the silicon surface were passivated with Me groups. The immobilized bipyridyl ligands bound metal ions, thus enabling assembly of metal complexes on the silicon surface. XPS studies demonstrated that [Cp*Rh(vbpy)Cl]Cl, [Cp*Ir(vbpy)Cl]Cl, and Ru(acac)2vbpy were assembled on the surface (Cp* is pentamethylcyclopentadienyl, acac is acetylacetonate). For the surface prepd. with iridium, X-ray absorption spectroscopy at the Ir L_(III) edge showed an edge energy and post-edge features consistent with a powder sample of [Cp*Ir(bpy)Cl]Cl (bpy is 2,2'-bipyridyl). Cyclic voltammetry data for surfaces prepd. on highly doped, conducting silicon confirmed electroactivity of the assembled complexes.