Premium
Comparing Ullmann Coupling on Noble Metal Surfaces: On‐Surface Polymerization of 1,3,6,8‐Tetrabromopyrene on Cu(111) and Au(111)
Author(s) -
Pham Tuan Anh,
Song Fei,
Nguyen ManhThuong,
Li Zheshen,
Studener Florian,
Stöhr Meike
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201504946
Subject(s) - scanning tunneling microscope , x ray photoelectron spectroscopy , covalent bond , chemistry , crystallography , dissociation (chemistry) , polymerization , density functional theory , annealing (glass) , polymer , materials science , computational chemistry , nanotechnology , chemical engineering , organic chemistry , engineering , composite material
The on‐surface polymerization of 1,3,6,8‐tetrabromopyrene (Br 4 Py) on Cu(111) and Au(111) surfaces under ultrahigh vacuum conditions was investigated by a combination of scanning tunneling microscopy (STM), X‐ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. Deposition of Br 4 Py on Cu(111) held at 300 K resulted in a spontaneous debromination reaction, generating the formation of a branched coordination polymer network stabilized by C−Cu−C bonds. After annealing at 473 K, the C−Cu−C bonds were converted to covalent C−C bonds, leading to the formation of a covalently linked molecular network of short oligomers. In contrast, highly ordered self‐assembled two‐dimensional (2D) patterns stabilized by both Br−Br halogen and Br−H hydrogen bonds were observed upon deposition of Br 4 Py on Au(111) held at 300 K. Subsequent annealing of the sample at 473 K led to a dissociation of the C−Br bonds and the formation of disordered metal‐coordinated molecular networks. Further annealing at 573 K resulted in the formation of covalently linked disordered networks. Importantly, we found that the chosen substrate not only plays an important role as catalyst for the Ullmann reaction, but also influences the formation of different types of intermolecular bonds and thus, determines the final polymer network morphology. DFT calculations further support our experimental findings obtained by STM and XPS and add complementary information on the reaction pathway of Br 4 Py on the different substrates.