Supramolecular assemblies of pyridyl porphyrin and diazadithia phthalocyanine

In this paper we report for the first time on a mixed complex between the cationic porphyrin 5, 10, 15, 20-tetra-N- -methyl-pyrydinium-p-il porphyrin (TMPyP) and a new metal phthalocyanine with four 16-membered diazadithia macrocycles (denoted here as Pc16), in order to obtain an active complex with an intense absorption on the lower energy side of the visible spectrum and with a higher sensitivity in photodynamic therapy of cancer. The dimerization constant for Pc16 and also the ratio between the oscillator strengths for monomeric and dimeric forms of this compound, were evaluated. The ratio between these oscillator strengths was 2.01 showing a certain dimerization process. The Job mathematical method allowed the establishment of the stoichiometry and the formation constants for the heteroaggregates between the porphyrin and the phthalocy- anine (a diad between one phthalocyanine molecule and one porphyrin molecule and a triad between two phthalocyanine molecules and only one porphyrin molecule). The coulombic attraction resulting from the p-p interaction of the two highly conjugated macrocycles and from the interaction between the substituents, favors a face-to-face geometry.