Formation of Dendrimer Nanoassemblies by Oligomerization-Induced Liquid-Liquid Phase Separation

Composition-defined nanosized assemblies that contain heterometallic early 4d/5d-transition-metals

The controlled assembly of early transition metals remains a challenging research target, especially with respect to the generation of heterometallic molecules and nanomaterials. In this study, metal chlorides of the early 4d/5d-transition-metals, i.e., ZrCl₄, NbCl₅, MoCl₅, HfCl₄, TaCl₅, and WCl₆, were stoichiometrically introduced into a tetraphenylmethane-core dendritic-phenylazomethine generation 4 dendrimer in the presence of an optimal amount of organic ligands such as pyridine and 3-chloropyridine. The coordinative interactions between the metal chlorides and the imines in the dendrimers indicated a positive correlation for the Lewis acidity of the metals. Moreover, it was clearly demonstrated for the first time that heterometallic assemblies of defined composition contain four kinds of early 4d/5d-transition-metals, such as Ta^V, Nb^V, Mo^V, and Zr^IV, which was confirmed by UV-vis titration, XPS, and HAADF-STEM/EDS measurements. The results of this study should provide access to new routes to produce nanomaterials composed of heterometallic early 4d/5d-transition metals.