Bottom-up synthesis and chemical functions of heterostructures of metal-cluster complexes

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This project has explored synthesis and characterizations of new potential-gradient molecular architectures where multiple units of redox-active moieties (including multinuclear complexes and organic ligands)are built up on Au electrode surfaces in a well-defined sequence. Here we have focused on the construction of molecular systems in which two different metal-cluster units are linked by a bridging ligand on a surface of Au(111) electrode. The hetero-molecular layers have been prepared by immersing an Au (111) electrode covered with the H_2O-terminated triruthenium SAM into a CH_2Cl_2 solution of a new ruthenium dimer. Here, the Ru_3 unit(bottom layer)and the Ru_2 unit (upper layer) are linked with 4,4'-bpy. Owing to the nature of proton-coupled electron transfer reaction in the ruthenium dimer, it was demonstrated that the potential gradient of molecular wire was controlled by pH of the electrolyte media in a reversible manner. Direct and facile immobilization of a solvent-terminated new diruthenium complex onto organic SAM was also demonstrated. For the triruthenium complex SAM, we examined electrolyte anion effects in redox potentials, reactivity of Ru_3 SAM with gaseous molecules such as CO and NO,^3 and photoreactivity. Another achievement in this project was a successful synthetic incorporation of a series of terapyrrol ligands and their metal complexes into the triruthenium complex.