  We investigate an anthracene derivative, 3(5)-(9-anthryl) pyrazole (ANP),
self-assembled on the Au (111) surface by means of scanning tunneling
microscopy (STM) and density functional theory (DFT) calculations. A
chessboard-like network structure composed of ANP molecules is found, covering
the whole Au (111) substrate. Our STM results and DFT calculations reveal that
the formation of chessboard-like networks originates from a basic unit cell, a
tetramer structure, which is formed by four ANP molecules connected through
C-H-N hydrogen-bonds. The hydrogen bonds inside each tetramer and the molecular
adsorption interaction are fundamentally important in providing a driving force
for formation of the supramolecular networks.
