Reversible aggregation of porphyrins in the solid state†

This paper reports the reversible aggregation of porphyrin molecules in a thin solid film. A commercially available molecule, p-meso-tetra(4-pyridyl)porphyrin (H2TPyP(4)), was used for these studies. Optical absorption spectroscopy of the solution and solid state forms of this molecule show that even in the solid state the molecules have enough mobility to undergo the movement required to form J-aggregates. Resonance light scattering (RLS), fluorescence spectroscopy and atomic force microscopy (AFM) are used to support these results.