Self-organization of amphiphilic porphyrins at the air-water interface

The Langmuir-Blodgett film forming properties of a series of pyridyl((hexadecyloxy)phenyl)porphyrins have been examined. Good monolayers of these compounds have been prepared in most cases without the use of matrix molecules and the monolayers are readily transferable to glassy slides. The small mean molecular areas, as obtained from the surface-pressure-area isotherms, indicate a tilted orientation of the porphyrin rings with respect to the water surface. It was found by means of UV-vis absorption spectroscopy at the air-water interface and by Brewster angle microscopy that intermolecular interaction between porphyrin rings mutually directs the organization at submonolayer coverage. Upon compression, the self-assembled domains come into close contact without reorganization of the layer structure. It was also demonstrated that porphyrins with three and four aliphatic side chains self-assembled into a highly-ordered arrangement in contrast to the porphyrins with one and two alkyl chains.