AN AMPHIPHILIC TRINUCLEAR COBALT CLUSTER-CONTAINING MOLECULAR UNIT - SYNTHESIS, CHARACTERIZATION AND LANGMUIR-BLODGETT-FILMS

An amphiphilic polynuclear transition-metal cluster has been prepared and its capability for forming layers at the air-water interface and Langmuir-Blodgett films on different substrates investigated. The compound was obtained by linking a Co3(CO)9 cluster to a hydrophobic cholesterol framework. A polar head was introduced by substituting one CO ligand by an isocyanide derivative bearing a hydrophilic functional group. The surface pressure and surface potential vs. area isotherms and Brewster-angle microscopy indicated the formation of stable Langmuir films. Up to thirty-six transfers were performed on hydrophobized solids (mica, glass, quartz and silicon wafers). Structural characterization of the transferred films (UV and IR spectroscopy, atomic force microscopy, small-angle X-ray scattering) demonstrated the formation of stable, highly organized crystals. The results represent a novel strategy towards the development of supramolecular assemblies from polynuclear transition-metal compounds and organometallic surfaces. The structure of [Co3(CO)8(CCO2Me)(CNC6H4CN)] has been established by X-ray crystallography.