Molecular Design of Amphiphiles Containing Mixed Ligand Transition Metal Complexes

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(1) Cobalt(III) and nickel(II) complexes having an alkyl long chain are newly prepared. They showed clear break points in the surface tension-concentration curves, indicating their aggregation in aqueous solutions. Critical micelle concentration (cmc) and surface tension reducing ability largely depended on the length of the alkyl-chain, the position of its substitution on the ligand, and counter ions. The results indicate that the structure of the complex part can influence the aggregation behavior considerably. Therefore, amphiphilic metal complexes are expected to be used to construct a variety of aggregation molphologies.(2) Mixed ligand amphiphilic cobalt(III) complexes containing N-dodecylethylenediamine and a chiral tetraamine provided a novel example that the chirality around the octahedral metal center affects the aggregation behavior of the complexes.(3) Solvatochromism was observed for a nickel(II)-tetraamine complex having a dodecyl chain, due to an interconversion between a paramagnetic octahedral (blue) and a diamagnetic square planar (orange) nickel complex. The interconversion of the steric structure of the polar head will be useful in designing amphiphiles whose aggregation can be highly controlled by external stimulations.