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Title: From hydrogen bonding to metal coordination and back: Porphyrin-based networks on Ag(111)

The self-assembly of a metal-free porphyrin bearing two pyridyl coordinating sites and two pentyl chains at trans meso positions was investigated under ultrahigh vacuum on a Ag(111) surface by scanning tunneling microscopy (STM). The STM measurements revealed a well-ordered close-packed structure with a rhombic unit cell for coverages ≤1 monolayer with their molecular plane parallel to the surface. The growth direction of the molecular islands is aligned along the step edges, which are restructured due to molecule-substrate interactions. The shorter unit cell vector of the molecular superstructure follows the 〈1-10〉 direction of the Ag(111) substrate. Hydrogen bonds between pyridyl and pyrrole groups of neighboring molecules as well as weak van der Waals forces between the pentyl chains stabilize the superstructure. Deposition of cobalt atoms onto the close-packed structure at room temperature leads to the formation of a hexagonal porous network stabilized by metal-ligand bonding between the pyridyl ligands and the cobalt atoms. Thermal annealing of the Co-coordination network at temperatures >450 K results in the transformation of the hexagonal network into a second close-packed structure. Changes in the molecule-substrate interactions due to metalation of the porphyrin core with Co as well as intermolecular interactions can explain the observed structural transformations.
Authors:
; ;  [1] ; ; ;  [2]
  1. Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AG Groningen (Netherlands)
  2. Laboratoire de Tectonique Moléculaire, UMR UDS-CNRS 7140, Université de Strasbourg, 4 rue Blaise Pascal, 67070 Strasbourg (France)
Publication Date:
OSTI Identifier:
22415485
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 10; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ANNEALING; ATOMS; CHEMICAL BONDS; COBALT; HYDROGEN; LIGANDS; MOLECULES; POROUS MATERIALS; PORPHYRINS; PYRROLES; SCANNING TUNNELING MICROSCOPY; SILVER; SUBSTRATES; SURFACES; TEMPERATURE RANGE 0273-0400 K; VAN DER WAALS FORCES