Novel PAMAM light-harvesting antennae based on 1,8-naphthalimide Synthesis, energy transfer, photophysical and pH sensing properties

This work presents the design convergent synthesis and spectral characteristics of novel PAMAM dendrons core and peripherally functionalized with 1 8-naphthalimide fluorophores The novel compounds were configured as light-harvesting antennae where the system surface is labeled with a different number of blue-emitting 4-allyloxy-1 8-naphthalimide donor fluorophores capable of absorbing light and efficiently transferring the energy to a single yellow-green emitting 4-alkylamino-1 8-naphthalimide acceptor dye The overlap between the blue emission of the donor periphery and the absorption of the acceptor (focal dye) was more than 95% Novel light-harvesting systems showed highly efficient energy transfer (91-94%) Nevertheless fluorescence quenching of the core chromophore was observed which is related to a possible photoinduced electron transfer (PET) from the 4-alkoxy-1 8-naphthalimide periphery towards the focal 4-alkylamino-1 8-naphthalimide Novel PAMAM light-harvesting systems were also configured in a "fluorophore-spacer-receptor format and as such displayed sensitive fluorescence signaling over a wide pH scale which is attributed to a PET process from the tertiary amines in the dendron bone to the fluorophores This assigns the synthesized light-harvesting antennae to potential use as highly efficient pH chemosensing materials (C) 2010 Elsevier B V All rights reserved