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Supramolecular Synthons on Surfaces: Controlling Dimensionality and Periodicity of Tetraarylporphyrin Assemblies by the Interplay of Cyano and Alkoxy Substituents
Author(s) -
Wintjes Nikolai,
Hornung Jens,
LoboCheca Jorge,
Voigt Tobias,
Samuely Tomáš,
Thilgen Carlo,
Stöhr Meike,
Diederich François,
Jung Thomas A.
Publication year - 2008
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.200800746
Subject(s) - alkoxy group , synthon , porphyrin , steric effects , supramolecular chemistry , chemistry , monolayer , crystallography , nanoporous , scanning tunneling microscope , stereochemistry , materials science , nanotechnology , crystal structure , organic chemistry , alkyl , biochemistry
Abstract 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.