Crystal-growth inhibition of solid porphyrin micro-crystals by G4 PAMAM dendrimer

We report on the effect of G4 PAMAM dendrimer on the formation of a previously reported solid porphyrin micro-crystals formed by two oppositely charged porphyrins [meso-tetra(N-methy-4-pyridyl)porphyrin tetratosylate (TMPyP) and zinc-tetrakis(4-sulphonatophenyl)porphyrin (Zn-TPPS)], by self-assembly at room temperature without acidification. The crystals were characterized by UV–visible spectroscopy, fluorescence spectroscopy, optical microscopy, and powder X-ray diffraction techniques. The addition of the G4 PAMAM dendrimer to the starting solution of the monomer porphyrins alters the size and morphology of the crystals as well as their absorbance and fluorescence spectra. However, the dendrimer is not incorporated in the structure.