FLUORESCENCE ENHANCEMENT IN AN UNSYMMETRICALLY-SUBSTITUTED COPPER PHTHALOCYANINE

Amongst all the properties that phthalocyanines possess, their photochemical behavior is extremely peculiar and useful for an extremely wide range of applications such as photodynamic therapy and photovoltaics. During the last years we have synthesized and tested a considerable number of new macrocyclic-based dyes for Dye-Sensitized Solar Cells bearing zinc in the central cavity. We have recently chosen to change the central ion to investigate the potentialities of other metals and we have focused our attention on copper derivatives because of their extremely high stability, fundamental for a long lifetime of the solar cell, and color intensity which is needed in order to maximize the light harvesting properties of the device. Even if Cu(II) is a well known fluorescence quencher because of its capability to induce an intersystem crossing in the molecular systems that interact with it, a consistent number of copper chlorines, porphyrins and corroles have been reported as photosensitizers1,2 showing interesting results in terms of efficiencies. Our contribution will deal with the fluorescence properties of some copper phthalocyanines with increasing degree of substitution synthesized as potential photochemical sensitizers, analyzed both with steady-state and time-resolved measurements. The results will be compared with those of the corresponding free-base and, when possible, zinc derivatives and in one specific case the evidence of a consistent fluorescence in a copper derivative has been highlighted.