Synthesis and self-organization characteristics of amide dendrons with focal ferrocenyl moiety

Abstract

Supramolecular materials are constructed from a variety of building blocks i.e. small molecules or macromolecules. In particular, self-organization of dendritic building blocks towards supramolecular architectures has been demonstrated in a thermotropic fashion, in aqueous phase, in organic media, and at solid-liquid interface. This approach has been of great interest in that it would provide a new route to functional supramolecular materials with precise shape and functionality. In our previous studies, we reported on the amide dendrons that can self-organize not only in organic media but also in aqueous phase. For example, dendron 1 forms thermoreversible supramolecular gels through selforganization of amide dendrons in organic media, and then lamella or columnar hexagonal arrays in dry state depending on the structures of the dendron building blocks. The key elements for self-organization are hydrogen bonding of the dendritic branches and van der Waals interactions of the alkyl peripheries for the stabilization of assembled structures. In addition, the amphiphilic nature due to the hydrophilic amide branches and the hydrophobic alkyl chains at the periphery provides an opportunity for the amide dendrons to self-organize in aqueous phase as well. For example, depending on the size of the hydrophilic MeO-PEG incorporated at focal moiety, the amide dendrons exhibited multiple morphologies such as vesicle, rod, and spherical micelle in water. The amide dendrons with a focal moiety of methyl ester also self-organize in water. The amide dendrons have capability of organizing various types of organic focal moieties into ordered states in aqueous phase. Therefore, we reasoned that the amide dendrons should be able to organize not only organic but also organometallic focal units into ordred state. Here, we report on the selforganization behavior of the amide dendrons with organometallic focal unit, ferrocenyl moiety in this work, in organic and aqueous media. This type of self-assembly of dendrons would provide a unique methodology for the construction of supramolecular materials which have functional elements in a well-defined fashion.