Perylenes are a well-known class of cromophores which have been widely studied due to their stiff structure and mostly flat-lying adsorption on surfaces which is caused because of the well-known attractive interation between their p-system and the metal surface. Thus, they became an archetypal system for studying structural, electrical and optical properties of organic thin films of them on various substrates. Moreover, nowadays basic (and also applied) research also focuses on the construction of 2D functional molecular architectures on solid substrates with perylenes as molecular building blocks.

In our work, we studied the adsorption behavior of two different perylene derivatives called DPDI (4,9-diaminoperylene-quinone-3,10-diimine) and TAPP (1,3,8,10-tetraazaperopyrene) on Cu(111). For DPDI depending on the initial coverage, three different well-organized arrangements are formed (figure 1, right) by annealing the samples at 300°C which leads to a dehydrogenation of the DPDI monomers [1] (figure1, left). The hexagonal honeycomb network exhibits the most appealing and stable organization on the surface. The pores can be used for the creation of hierarchical structures. In particular, the properties of C60 and ZnOEP trapped in the pores were investigated in detail. C60 could be successfully repositioned with the STM tip and even an artificial C60 -porphyrin complex was assembled (figure 2, left). ZnOEP displays a thermally activated hindered rotation inside the pores. [3] (figure 3b, down).

TAPP molecules self-assemble into a porous network on Cu (111) surface after annealing at 150°C as a result of tautomerization process (figure 4, left). After annealing at 250°C polymeric chains appear (figure 4, right) which can also be manipulated by the STM tip and shows a reversible bending and elasticity.

[1] Meike Stöhr, Marcus Wahl, Christian H. Galka, Till, Riehm, Thomas Jung, Lutz H. Gade, “Controlling Molecular Assembly in Two Dimensions: The Concentration Dependence of Thermally Induced 2D Aggregation of Molecules on a Metal Surface”
Angew. Chem. Int. Ed. 2005, 44, 7394-7398.
[2] Meike Stöhr, Marcus Wahl, Hannes Spillmann, Lutz H. Gade, Thomas, Jung “Lateral Manipulation for the Positioning of Molecular Guests within the Confinements of a Highly Stable Self-assembled Organic Surface Network”
Small 2007, 3, No 8, 1336-1340.
[3] Marcus Wahl, Meike Stöhr, Hannes Spillmann, Thomas Jung, Lutz H. Gade “Rotation-libration in a Hierarchic Rotor-stator System: Arrhenius Activation and Retardation by Local Interaction”
Chem. Commun. 2007, 1349-1351.
[4] Manfred Matena, Till Reihm, Meike Stöhr, Thomas Jung, Lutz H. Gade “ Transforming Surface Coordination Polymers into Covalent Surface Polymers: Linked Polycondensed Aromatics through Oligomerization of N-Heterocyclic Carbine Intermediates”
Angew. Chem. 2008, 120, 2448-2451.

Figure 3. (up) STM images (16nm x 16nm) showing the different thermal behaviour of the ZnOEP molecules trapped in the pores of the dehydro-DPDI honeycomb network. The rotation speed of the guest molecules is slowed down going from the RT to 5K. (down) Model to explain the thermally induced hindered rotation of ZnOEP trapped inside the pores of the dehydro-DPDI network. Two subsequent 30° rotations of the confined ZnOEP molecule with respect to the hexagonal network are illustrated. A possible peripheral position of the STM tip is indicated by the red circle and clearly demonstrates the alternation of the molecular environment.

Figure 4. (left) STM image showing the porous TAPP network. Four molecules and four Cu-atoms are superposed to display their arrangement. (right) STM image of the TAPP chains formed after annealing the sample at 250°C.