The initial growth behavior and structures of free base and metal complexes of 5,10,15,20-tetrakis(3,5-di-t-butylphenyl)porphyrin (H-2-TBPP, M-TBPP) on Cu(100) surface were studied by scanning tunneling microscopy. Conformational flexibility of H2-TBPP led to bridging over the step edges and to formation of single supramolecular chains on the step edges, which were separated from the supramolecular islands on the terraces. M-TBPP adsorbed on the upper and lower edge of the step and 2D growth of islands began from here. These results suggest that the step edges could be useful as a template for fabrication of well-ordered single supramolecular chains. (c) 2005 Elsevier B.V. All rights reserved.