Linear and branched Fe(tpy)(2) complex oligomer wires were quantitatively formed on hydrogen-terminated silicon wafers by means of hydrosilylation of ethynylterpyridine and following stepwise coordination reactions, and the redox property of surface-attached species and its photosensitivity can be controlled by the doping density of the silicon wafers.

Formation of silicon-aryl and germanium-aryl direct bonds on the semiconductor surface is a key issue to realize molecular electronic devices, but the conventional methods based on radical intermediates have problems to accompany the side reactions. We developed the first example of versatile and efficient methods to form clean organic monolayers with Si-aryl and Ge-aryl bonds on hydrogen-terminated silicon and germanium surfaces by applying our original catalytic arylation reactions of hydrosilanes and hydrogermanes using Pd catalyst and base in homogeneous systems. We could immobilize aromatic groups with redox-active and photoluminescent properties, and further applied in the field of rigid π-conjugated redox molecular wire composites, as confirmed by the successive coordination of terpyridine molecules with transition metal ions. The surfaces were characterized using cyclic voltammetry (CV), water contact angle measurements, X-ray photoelectron spectroscopy (XPS), fluorescence spectroscopy, and atomic force microscopy (AFM). Especially, the AFM analysis of 17 nm-long metal complex molecular wires confirmed their vertical connection to the plane surface.

p-Conjugated bis(terpyridine)metal (M(tpy) 2 ) oligomer wires were prepared by surface coordination programming such that they displayed an inherent potential gradient along the wire through the chain of metals and bridging ligands. The electron transfer properties of these wires were examined. Heterometal complex wires prepared in the sequence Au(111)-Co(tpy) 2 -Fe(tpy) 2 -ferrocene (Fc); that is, Au-[A azo -1CoL H -1FeT Fc ] ((A azo ) 2 ¼ bis((4-(4 0 -2,2 0 ;6 0 ,2 00 -terpyridyl)phenylazo)phenyl)disulfide, L H