Sierpiński triangles formed by molecules with linear backbones on Au(111)

Fractals play an important role in mathematics, aesthetic, science, and engineering. The representative Sierpinski-triangle fractals have been successfully constructed by V-shape molecules in experiments. The molecular Sierpinski triangles formed by molecules with linear backbones have been theoretically predicted but not experimentally discovered. To achieve this goal in the experiment, we used[1,1’;4’,1’’;4’’,1’’’]-quaterphenyl-3,40 0-dicarbonitrile molecules as building blocks and employed cobalt atoms as cements, then successfully obtained metal-organic Sierpinski triangles with an order up to 2 on the Au(111) surface. There are twenty-four types of three-fold coordination nodes formed between the metal atom and organic ligands via coordinate interactions. The coexistence of various nodes is responsible for that the highest order of Sierpinski triangles is limited to 2.