Supramolecular Synthons on Surfaces: Controlling Dimensionality and Periodicity of Tetraarylporphyrin Assemblies by the Interplay of Cyano and Alkoxy Substituents

The self‐assembly of three porphyrin derivatives was studied in detail on a Cu(111) substrate by means of scanning tunneling microscopy (STM). All derivatives have two 4‐cyanophenyl substituents in diagonally opposed meso‐positions of the porphyrin core, but differ in the nature of the other two mes...

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Bibliographic Details
Published in:Chemistry : a European journal 2008-06, Vol.14 (19), p.5794-5802
Main Authors: Wintjes, Nikolai, Hornung, Jens, Lobo-Checa, Jorge, Voigt, Tobias, Samuely, Tomáš, Thilgen, Carlo, Stöhr, Meike, Diederich, François, Jung, Thomas A.
Format: Article
Language:English
Subjects:
molecular recognition
networks on surfaces
porphyrinoids
scanning probe microscopy
supramolecular chemistry
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Summary:The self‐assembly of three porphyrin derivatives was studied in detail on a Cu(111) substrate by means of scanning tunneling microscopy (STM). All derivatives have two 4‐cyanophenyl substituents in diagonally opposed meso‐positions of the porphyrin core, but differ in the nature of the other two meso‐alkoxyphenyl substituents. At coverages below 0.8 monolayers, two derivatives form molecular chains, which evolve into nanoporous networks at higher coverages. The third derivative self‐assembles directly into a nanoporous network without showing a one‐dimensional phase. The pore‐to‐pore distances for the three networks depend on the size and shape of the alkoxy substituents. All observed effects are explained by 1) different steric demands of the alkoxy residues, 2) apolar (mainly dispersion) interactions between the alkoxy chains, 3) polar bonding involving both cyanophenyl and alkoxyphenyl substituents, and 4) the entropy/enthalpy balance of the network formation. Optimum coverage: The self‐assembly of three different tetrakis(meso‐phenyl)porphyrins with cyano and different alkyloxy substituents is studied on Cu(111) by STM (see graphic). At coverages below 0.8 monolayers (ML), two of these porphyrins show chainlike assemblies, which transform into nanoporous networks with different pore‐to‐pore distances at higher coverages, whereas the third molecular component self‐assembles directly into a nanoporous network.
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.200800746