Properties of Porphyrin- and Phthalocyanin-Monolayers at Metal-Electrolyte Interfaces

The adsorption of organic layers on solid surfaces is a promising route to produce surfaces of designed functionality. In this lecture an overview will be given about state-of-the-art investigations of the structural and chemical properties of porphyrin- and phthalocyanin-monolayers adsorbed electrochemically in the form of their molecular cations on anion-modified single-crystal metal electrode surfaces as a function of the nature of the metal (copper, gold), the kind of the pread-sorbed anions (chloride, iodide, sulfate), the symmetry of the surface ((100), (111)), and the electro-chemical potential, using besides classical electrochemical methods Electrochemical Scanning Tunneling Microscopy (EC-STM), and ex-situ Synchrotron X-Ray Photoelectron Spectroscopy (S-XPS). Particular attention will be paid to the self-assembly- vs. template-effects in the structure formation process, to structural phase transitions as a function of electrochemical potential, as well as to the chemical reactivity of selected porphyrins and phthalocyanins. Fig. 1b shows 5,10,15,20-Tetrakis(4-trimethylammonio-phenyl)porphyrin molecules adsorbed on a Cl-precovered Cu(111) surface. Instead of the threefold symmetry of the substrate (Fig. 1a) the molecules self-assemble into a square molecular superlattice (Fig.1b) [1]. Fig.2 shows coexisting square and hexagonal structure domains of 3-pyridyloxy-appended phthalocyanine on iodide precovered Cu(100) [2].

References

[1] Thanh Hai Phan, Tomasz Kosmala, and Klaus Wandelt, in preparation

[2] Thanh Hai Phan, Stephan Breuer, Uwe Hahn, DucThanh Pham, Tomás Torres, and Klaus Wandelt,

      J.Phys.Chem.C, submitted

 Fig. 1 5,10,15,20-Tetrakis(4-trimethylammonio-phenyl)porphyrin               Fig. 2 3-pyridyloxy-phthalocyanine

                                     on Cl-precovered Cu(111) [1]                                   on iodide precovered Cu(100)   [2].