Surface aggregate morphology of chiral porphyrins as a function of constitution and amphiphilic nature

The deposition of molecules onto surfaces from dilute solutions can lead to a variety of layer morphologies depending on the balance of interactions between solvent and molecule, molecules themselves, and these two components and the surface. Here we explore the behaviour of a set of chiral tetra meso-amidophenyl-substituted porphyrins-containing long hydrophobic tails at the periphery of the conjugated pi-electron system-after depositing a drop of each compound from different solutions onto graphite. The synthesis of the new compounds is detailed and the morphology of the aggregates they form on the substrate has been investigated by atomic force microscopy (AFM). Depending on the solvent used and composition and constitution of the compound the structures formed are very different. Round shape aggregates and larger dewetting type patterns were formed from solutions of the compounds in methanol-in which all the molecules exhibit non-specific aggregation-and when chloroform and toluene are used fibril-like structures appear, whose alignment with the graphite axes depends on the length of the alkyl chains attached to the amide moiety in the molecules.