“Click” Synthesis of Intrinsically Hydrophilic Dendrons and Dendrimers Containing Metal Binding Moieties at Each Branching Unit

Abstract

A new family of water-soluble triazole dendrimers composed of tri(ethylene glycol) (TrEG) and bis(methylol)propionic acid (bis-MPA) was created through Cu(I)-catalyzed alkyne–azide cycloaddition (CuAAC) between specifically designed complementary building blocks. Dendrimers up to generation three were synthesized by CuAAC to a trifunctional core with yields ranging from 72% for generation one, through 67% for generation two, and 64% for third generation dendrimer. The two triazole rings at each bis-MPA branching site could serve as efficient chelating pockets for some VIIIA group elements. As proof-of-principle, the [PdCl2(PhCN)2] coordination chemistry of these hydrophilic dendritic ligands was studied by 1H NMR, dynamic light scattering, transmission electron microscopy, and DFT calculations. The results showed that the complexation is completed within 5 min. The novel hydrophilic dendritic Pd complexes were able to catalyze Suzuki–Miyaura coupling reactions in water within 3 h at 100 °C, at 60 °C, and even at 50 °C with practically quantitative conversion.