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Tetrakis(4-pyridyl)porphyrin Supramolecular Complexes with Cyclodextrins in Aqueous Solution

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ABSTRACT

The formation of inclusion complexes of hydroxypropyl-β-cyclodextrin, heptakis(2,6-di-O-methyl)-β-cyclodextrin and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin with 5,10,15,20-tetrakis(4-pyridyl)porphyrin (TpyP) has been studied in aqueous buffer solution (phosphate buffer pH = 7 and I = 0.01 M) to give a structural and spectroscopic characterization of a new class of potential sensitizers for photodynamic therapy. The interaction was investigated by a combination of UVNis absorption, fluorescence anisotropy, time-resolved fluorescence and circular dichroism. The experimental results point to the presence of the pigment in water in a monomeric complexed form. The fluorescence anisotropy measurements suggest that TpyP forms 1:1 complexes with heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin and hydroxypropyl-β-cyclodextrin, while 1:2 complexes are obtained with heptakis(2,6-di-O-methyl)-β-cyclodextrin.

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