2Hâ Tetrakis(3,5â diâ tertâ butyl)phenylporphyrin on a Cu(110) Surface: Roomâ Temperature Selfâ Metalation and Surfaceâ Reconstructionâ Facilitated Selfâ Assembly

Abstract

The adsorption behavior of 2Hâ tetrakis(3,5â diâ tertâ butyl)phenylporphyrin (2HTTBPP) on Cu(110) and Cu(110)â (2Ã 1)O surfaces have been investigated by using variableâ temperature scanning tunneling microscopy (STM) under ultrahigh vacuum conditions. On the bare Cu(110) surface, individual 2HTTBPP molecules are observed. These molecules are immobilized on the surface with a particular orientation with respect to the crystallographic directions of the Cu(110) surface and do not form supramolecular aggregates up to full monolayer coverage. In contrast, a chiral supramolecular structure is formed on the Cu(110)â (2Ã 1)O surface, which is stabilized by van der Waals interactions between the tertâ butyl groups of neighboring molecules. These findings are explained by weakened moleculeâ substrate interactions on the Cu(110)â (2Ã 1)O surface relative to the bare Cu(110) surface. By comparison with the corresponding results of Cuâ tetrakis(3,5â diâ tertâ butyl)phenylporphyrin (CuTTBPP) on Cu(110) and Cu(110)â (2Ã 1)O surfaces, we find that the 2HTTBPP molecules can selfâ metalate on both surfaces with copper atoms from the substrate at room temperature (RT). The possible origins of the selfâ metalation reaction at RT are discussed. Finally, peculiar irreversible temperatureâ dependent switching of the intramolecular conformations of the investigated molecules on the Cu(110) surface was observed and interpreted.Role of the substrate: 2Hâ Tetrakis(3,5â diâ tertâ butyl)phenylporphyrin (2HTTBPP) molecules can selfâ metalate with copper atoms from the substrate on both Cu(110) and Cu(110)â (2Ã 1)O surfaces at room temperature (RT; see figure). The (2Ã 1) surface reconstruction of Cu(110) by oxygen atoms also significantly modifies the moleculeâ substrate interaction and facilitates the selfâ assembly of 2HTTBPP molecules at RT.