| Abstract
| - The synthesis of a new family of phosphorus dendrimers built from an octasubstituted metal-free phthalocyanine core is described up to generation 5. This core is used as a sensor and a probe foranalyzing the properties of the internal structure and the influence of each structural part (core, branches,surface) upon the whole structure. UV−visible spectra show both a hyperchromic and bathochromic effecton the Q-bands with increasing generation, indicating that the chromophore is more isolated, and that thedendritic shell mimics a highly polar solvent. There is no evidence for aggregation, except for generation0, showing again the isolation of the core. However, the dendritic shell is permeable to aqueous acids andbases, as demonstrated by the reversible splitting of the Q-band in an acidic medium (neutral form of thephthalocyanine) and the single Q-band in a basic medium (dianionic form), even for generation 4. Thefluorescence quantum yield for the neutral form increases with increasing generation. The dianionic formof generation 0 is poorly fluorescent, whereas generations 3 and 4 (G3 and G4) exhibit better fluorescence.The cores of G3 and G4 are highly sensitive optical sensors for H3O+ and OH-. These experiments arecarried out in THF/water mixtures, and the influence of water on the structure has been checked. Thehydrodynamic radius of generation 4 is measured by NMR diffusion (pulse gradient spin−echo) experiments.RH varies from 35.4 Å at 4 mol % of water to 32.5 Å at 64 mol % of water in THF, indicating the hydrophobicnature of these dendrimers.
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