Porphyrin derivatives are well-known to have unique photochemical, electrochemical and catalytic properties and then have extensively used as a building block in construction of molecular devices. In order to construct molecular devices using porphyrin with higher efficiency, we should control porphyrin ring orientation, namely porphyrin ring should be adsorbed parallel to the substrate surface. Moreover, ordered multilayers of porphyrins can be constructed by alternating construction of ligand and porphyrin layers if the flatly adsorbed porphyrin monolayer is formed on the substrate surface as a first layer. In this report, a novel porphyrin derivative with 4 thiol groups as surface binding groups to gold, 5,10,15,20-tetrakis(m-mercapto-p-methoxyphenyl) porphyrin (TMMPP) was designed and synthesized, and self-assembly process of TMMPP on Au(111) single crystal surface was investigated by electrochemical and scanning tunneling microscopy (STM) measurements.After annealing and quenching of Au(111) single crystal disk, TMMPP self-assemled monolayer (SAM) on Au(111) was prepared by dipping the Au(111) substrate into benzene solution containing 0.05 mM TMMPP for certain periods. Linear sweep voltammograms of the Au(111) electrodes modified with TMMPP SAM, which was prepared for several dipping periods, were measured in 0.1 M KOH solution. Ex situ STM measurement of each TMMPP SAM on Au(111) was performed in air at room temperature.Based on the experimental results, we found that TMMPP molecule was flatly adsorbed in the initial stage of SAM formation process and flatly adsorbed TMMPP was arranged in order on the atomic arrangement of the underlying Au(111) surface at the final stage of TMMPP self-assembly.

Formation process studies of flatly oriented porphyrin self-assembled layers on Au(111)

247th National Meeting (2014)

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