Orientation of differently substituted phthalocyanines: First layers and thin films

The molecular orientation of the first layers and thin films of differently substituted phthalocyanines on gold substrates is compared. Due to a relatively strong molecule-substrate interaction the orientation is parallel to the sample surface for all materials in the first layers. At higher film thickness the orientation is determined by the substituents. Materials with short substituents prefer standing orientation, implying the substituents do not inhibit the intermolecular interactions. Molecules with long substituents are not able to build up the same aggregates, they grow disordered in the upper layers.