Poly(amidoamine) Dendrimers Bearing Electron-Donating Chromophores: Fluorescence and Electrochemical Properties

Abstract

Poly(amidoamine) dendrimers from the zeroth generation (G 0) to the fifth generation (G 5) bearing electron-donating chromophores, i.e. N, N-dimethylphenylamine (PA), carbazole (Cz) and pyrene (Py) chromophores have been synthesized. The macromolecular reactions of chromophoric modifications of PAMAM dendrimers were monitored by fluorescence spectroscopy. The reliability of fluorescence monitoring was confirmed by NMR spectroscopy. Compared with widely applied environment-sensitive fluorescence probe techniques, a distinct feature of the fluorescence monitoring was that it directly reflected the conversion of chemical bonds. A comparative study revealed that the fluorescence quenching of small molecular Py by the high generation dendrimers of PAMAM-PA was a static quenching process. The high generation dendrimers of PAMAM-Py possessed relatively compact Py shells as compared with the same generation PAMAM-PA. Electrochemical studies revealed an architectural transition occurring from an open and flexible structure to a closely packed globular structure between G 2 and G 3. The electron-donating ability of PAMAM-PA was affected by dendritic architectures.