Tetragonal porous networks made by rod-like molecules on Au(111) with halogen bonds

Abstract

Supramolecular structures of two rod-like molecules whose both ends are terminated with Br-ligands were studied using scanning tunneling microscopy (STM). Rectangular and square porous networks were observed in 4,4 ''-dibromo-p-terphenyl (DBTP) and 4,4 ''-dibromo-p-quaterphenyl (DBQP) molecules on Au(1 1 1) with the void areas of 3.5 and 5.6 nm(2), respectively. Both networks had chiral quadrupole nodes that could be explained with four Br center dot center dot center dot Br halogen bonds and four Br center dot center dot center dot H hydrogen bonds. The reversible transformations of network structures were observed in consecutive STM images, possibly mediated by a liquid phase surrounding the networks. The molecules also formed close-packing ladder-like networks with triple nodes that could be explained with four Br center dot center dot center dot H bonds. Our study shows that Br-ligands play key roles in forming molecular networks for both rod-like molecules. (C) 2014 Elsevier B.V. All rights reserved.