Self-Assembly Structures of a Phenol-Substituted Porphyrin in the Solid State: Hydrogen Bonding, Kagomé 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) Å, b = 13.631(2) Å, c = 15.060(3) Å, β = 105.720(4)°, and U =
2514.9(7) Å3. 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 Kagomé 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 × 4l [where l is the
Cu(111) lattice constant].