We studied the formation of linked porphyrin oligomers from 5,15-diphenylporphyrin (2H-DPP) by thermal, substrate-assisted organometallic and dehydrogenation coupling on Cu(111) by scanning tunneling microscopy. In the range of 300-620 K, we find three distinct stages, at 300 K, the intact 2H-DPP molecules self-assemble into linear structures held together by van der Waals forces. Increasing the substrate temperature, self-metalation and intramolecular ring-closing reactions result in planar and isolated DPP species on the surface. By C-H cleavage, porphyrin oligomers bonded by organometallic and covalent bonds between the modified DPP are formed. The amount of covalently bonded DPP oligomers increases strongly with annealing time and temperature, and they become the dominant species at 570 K. In contrast, the number of organometallically bonded DPP oligomers increases moderately even up to 620 K, indicating that in this case the organometallic bond is no precursor of the covalent bond.
We explore the behavior of two-dimensional patchy colloidal particles with 8 or 10 symmetrically arranged patches by employing Monte-Carlo simulations. The particles interact according to an isotropic pair potential that possesses only one typical length. The patches lead to additional attractions that are anisotropic and depend on the relative orientation of two neighboring particles. We investigate the assembled structures with a special interest in quasicrystals. We found that the patch width is of great importance: Only in case of narrow patch widths we are able to observe metastable octagonal and decagonal quasicrystals, while dodecagonal quasicrystals can also occur for broad patches. These results are important to understand the role of interactions with preferred binding angles in order to obtain quasicrystals. Our findings suggest that in case of sharp binding angles, as they occur in metallic alloys, octagonal and decagonal symmetries might be observed more often than in systems with less sharp binding angles as it is the case in soft matter systems where dodecagonal quasicrystals dominate.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.