Novel Functional Groups with Fine-Controlled Metal Assembling Function

Abstract

Abstract Half-substituted dendritic phenylazomethine dendrimers with various substituents (Half-DPA-X Gn, where n is the generation number) were synthesized in order to elucidate the electron gradients in the dendrons by complexation with metal ions. Along with the change in the UV–vis spectra, the isosbestic point shifted about 11 nm from 371 to 360 nm. The number of added equivalents of SnCl2 required to induce a shift was in agreement with the number of the imine sites present in each layer of Half-DPA-H G4. The degree of the electron gradient in the phenylazomethine monodendrons, Half-DPAs, was estimated via titration with trifluoroacetic acid. We found drastic differences in the basicity of the imine sites; the basicity of the core imines is higher than that of the more peripheral imines. The stepwise complexation behavior is thermodynamically controlled from the core to terminal imines in Half-DPA-H. Furthermore, Half-DPA G4 with various substituents possesses the same electron gradients in the dendron, so the complexation behavior with metal ions is the same.