Fabrication and Functions of Molecular Assemblies based on 2D Surface Coordination Chemistry

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1) Molecular self-assembly of metal complexes on solid surface: The layer-by-layer growth by the use of coordination bond is one of the promising synthetic strategy for the construction of well-defined nanostructure on the surface. Redox-active rod-shaped metal complexes bridged by bis tridentate ligands are stereochemically defined, and therefore these complexes are one of potential candidates for molecular devices. We have synthesized several new Ru/Os complexes containing tridentate 2,6-bis(benzimidazol-2-yl)pyridine with disulfide (bimpy-S) or phosphonate (bimpy-P) groups as a anchoring group. These [M(bimpy-S)(bimpy-P)] or [M(bimpy-P)2] complexes (M = Ru and Os) were self-assembled on gold or ITO electrode. Layer-by-layer growth was achieved by the successive immersion of the solid substrate to [M(bimpy-P)2] complex in CH3CN and Zr(IV) aqueous solution, and monitored by the UV spectra and electrochemical technique. The absorbance of MLCT band at 500 nm was linearly increased with … More increasing the number of layers, at the 2) 2D coordination chemistry at the air-water interface: In order to control the formation of coordination polymer between the metal ion and ligand such as 4,41-bipyridien, "two-dimensional coordination chemistry" at the air-water interface was developed by using the Langmuir-Blodgett technique. Surface pressure-area (p-A) isotherm of amphiphilic ligand, 3,3'-bis(N,N'-dioctadecylamide)-4,4'-bipyridine ( 1 ) , on pure water subphase shows a liquid expanding phase at a molecular area of 0.45 nm2 and then a liquid condensed phase with a limiting molecular area of 0.40 nm2 molecule-1 close to that expected from a molecular modeling. The change of subphase from pure water to aqueous solution containing metal sulfate (MSO4) leads to a large expansion of molecular area, accompanied by a phase transition. The molecular limiting areas are 0.61 nm2 and 0.45 nm2 for the first and second phases of Ni2+, respectively. The AFM images of 1 transferred from Ni2+-contained subphase reveals the sheet domain morphology with rectangle pinholes oriented to the same direction at the transferred surface pressure of 5 mNm-1. Less