Development of Ordered Monolayer Based on the Self Assembly of Molecular Tripods

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1) Synthesis of Molecular Tripod-Ferrocene Dyads and Their MonolayersDyads consisting of a molecular tripod and ferrocene, connected through oligo (phenyleneethynylene) linkers of different lengths, were synthesized. The tripod has a rigid adamantane core to which three CH_2SH legs are attached in order to enable chemisorption on gold surface. The self-assembled monolayers of these dyads were prepared on Au (111) surface and analyzed by means of electrochemical measurements. The surface densities of the monolayers were shown to be constant irrespective of the length of the linker, demonstrating that the adjacent ferrocene units are fixed with a uniform intermolecular distance due to the rigid framework of adamantane and linear linker. It was also shown that there is negligible interaction among neighboring ferrocene units. This indicates that each ferrocene unit is kept independent from adjacent molecules, suggesting that these dyads are of potential use as molecular memories.2) Synthesis of an Extended Molecular Tripod and Its MonolayerA new adamantane tripod, having C(CH_3)2SH groups in place of the CH_2SH groups, was synthesized. Owing to the bulkiness of the two methyl groups, each tripod molecule is expected to occupy an increased area, resulting in greater molecular distance. Reductive desorption experiments for the self-assembled monolayer on Au(111) surface of this new trithiol showed that the molecular distance is significantly wider(10.9 A) than without the methyl groups. Future synthesis of dyads of this new tripod and functional molecular units would enable formation of monolayers of large-sized functional molecules