A spectroscopic study of self-assembled monolayer of porphyrin-functionalized oligo(phenyleneethynylene)s on gold: the influence of the anchor moiety
Journal article, 2008

Porphyrin-functionalized oligo(phenyleneethynylene)s (OPE) are promising molecules for molecular electronics applications. Three such molecules (1-3) with the common structure P-OPE-AG (P and AG are a porphyrin and anchor group, respectively) and different anchor groups, viz. an acetyl protected thiol, -S-COCH 3 (1), an acetyl protected thiol with methylene linker, -CH 2 -S-COCH 3 (2), and a trimethylsilylethynyl group, -C≡C-Si(CH 3 ) 3 (3) have been synthesized and the corresponding self-assembled monolayers (SAMs) on Au(111) substrates have been prepared. The integrity and structural properties of these films were studied by X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy. The results suggest that the films formed from 1 have a high orientational order with an almost upright orientation and dense packing of the molecular constituents, i.e. represent a high quality SAM. In contrast, molecule 2 formed disordered molecular layers on Au, even though the molecule-surface bonding (thiolate) is the same as in the case of molecule 1. This suggests that the methylene linker in molecule 2 has a strong impact on the quality of the resulting film, so that a well-ordered SAM cannot be formed. The silane system, 3, is also able to bind to the gold surface but the resulting SAM has a poor quality, being significantly disordered and/or comprised of strongly inclined molecules. The above results suggest that the nature of the anchor group along with a possible linker is an important parameter which, to a high extent, predetermines the entire quality of OPE-based molecular layers.


S. Watcharinyanon

Karlstad University

Daniel Nilsson


E. Moons

Karlstad University

A. Shaporenko

Heidelberg University

M. Zharnikov

Heidelberg University

Bo Albinsson

Chalmers, Chemical and Biological Engineering, Physical Chemistry

Jerker Mårtensson

Chalmers, Chemical and Biological Engineering, Organic Chemistry

L. S. O. Johansson

Karlstad University

Physical Chemistry Chemical Physics

1463-9076 (ISSN) 1463-9084 (eISSN)

Vol. 10 34 5264-5275

Subject Categories

Chemical Sciences



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