title: Assembling molecular Sierpiński triangle fractals.
abstract: Fractals, being "exactly the same at every scale or nearly the same at different scales" as defined by Benoit B. Mandelbrot, are complicated yet fascinating patterns that are important in aesthetics, mathematics, science and engineering. Extended molecular fractals formed by the self-assembly of small-molecule components have long been pursued but, to the best of our knowledge, not achieved. To tackle this challenge we designed and made two aromatic bromo compounds (4,4″-dibromo-1,1':3',1″-terphenyl and 4,4‴-dibromo-1,1':3',1″:4″,1‴-quaterphenyl) to serve as building blocks. The formation of synergistic halogen and hydrogen bonds between these molecules is the driving force to assemble successfully a whole series of defect-free molecular fractals, specifically Sierpiński triangles, on a Ag(111) surface below 80 K. Several critical points that govern the preparation of the molecular Sierpiński triangles were scrutinized experimentally and revealed explicitly. This new strategy may be applied to prepare and explore various planar molecular fractals at surfaces.
authors.affiliation: SKLSCUSS, BNLMS, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Shang
authors.affiliation: Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871, China.
authors.forename: Yongfeng
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse, Marburg 35032, Germany.
authors.forename: Min
authors.initials: M
authors.lastname: Chen
authors.affiliation: SKLSCUSS, BNLMS, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
authors.forename: Jingxin
authors.initials: J
authors.lastname: Dai
authors.affiliation: SKLSCUSS, BNLMS, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
authors.forename: Xiong
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse, Marburg 35032, Germany.
authors.forename: Julian
authors.initials: J
authors.lastname: Kuttner
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse, Marburg 35032, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Hilt
authors.affiliation: Department of Chemical Physics, School of Chemistry and Materials Science, University of Science and Technology of China, Hefei 230026, China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Shao
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse, Marburg 35032, Germany.
authors.forename: J Michael
authors.initials: JM
authors.lastname: Gottfried
authors.affiliation: 1] SKLSCUSS, BNLMS, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China [2] SPURc, 1 CREATE Way, #15-01, CREATE Tower, Singapore 138602, Singapore.
authors.forename: Kai
authors.initials: K
authors.lastname: Wu