Pyrene-labeled dendrimers functionalized with fullerene C₆₀ or porphyrin core as light harvesting antennas

Pyrene-labeled dendrimers linked to a fullerene C₆₀ or a porphyrin core were designed and synthesized through a convergent synthetic pathway. The energy transfer process that is occuring inside the obtained dendrimers was studied by measuring and analysing their absorbance and fluorescence emission properties. All absorption spectra are showing the typical absorption band of pyrene. No ground state interaction was detected between pyrene and porphyrin whereas a slight interaction was observed between pyrene and fullerene C₆₀. An almost quantitative quenching of the pyrene fluorescence emission was observed when coupled with fullerene C₆₀ as well as with porphyrin, indicating effective energy transfer. In the case of fullerene C₆₀, no emission could be seen due its weak intrinsic emission. When the acceptor was a porphyrin moiety, fluorescence emission was observed from the free porphyrin as well as from the Zn complex analogue.