Self-assembly structures of a phenol-substituted porphyrin in the solid state: Hydrogen bonding, Kagome lattice, and defect tolerance

The X-ray crystal structure and surface-adsorbed self-assembled structures of the porphyrin 5,10,15,20-tetrakis(3,5-dimethyl-4-hydroxyphenyl)porphyrin (1) were investigated. This compound crystallizes in the space group P2(1)/n with a = 12.727(2) angstrom, b = 13.631(2) angstrom, c = 15.060(3) angstrom, beta = 105.720(4)degrees, and U = 2514.9(7) angstrom(3). The molecules are held in a hatchlike structure with linear arrays of the molecules arranged approximately orthogonally under the strong influence of hydrogen-bonding interactions involving phenolic protons and porphyrin imino nitrogen atoms. Hydrogen-bonding interactions also dictate the surface adsorbed structures with modulation by the underlying substrate lattice [in this case, Cu(111)]. At submonolayer substrate coverage, the molecules exhibit a variety of structural motifs. There is a tendency toward the formation of cyclic trimeric species that are surface-mobile and can act as precursors in the formation of a Kagome 2D porous network structure. At monolayer coverage, molecules of 1 adopt a herringbone-type structure superimposed on linear arrays. The molecular conformation of 1 is dictated by the substrate lattice, with methyl groups of 1 lying at lattice vertices, giving a molecular footprint of dimensions 5l x 4l [where l is the Cu(111) lattice constant].