Growth of Thin, Anisotropic, π-Conjugated Molecular Films by Stepwise "click" Assembly of Molecular Building Blocks: Characterizing Reaction Yield, Surface Coverage, and Film Thickness versus Addition Step Number

Abel T. Demissie, Greg Haugstad, C. Daniel Frisbie

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

We report the systematic characterization of anisotropic, π-conjugated oligophenyleneimine (OPI) films synthesized using stepwise imine condensation, or "click" chemistry. Film synthesis began with a self-assembled monolayer (SAM) of 4-formylthiophenol or 4-aminothiophenol on Au, followed by repetitive, alternate addition of terephthalaldehyde (benzene-1,4-dicarbaldehyde) or 1,4-benzenediamine to form π-conjugated films ranging from 0.6-5.5 nm in thickness. By systematically capping the OPI films with a redox or halogen label, we were able to measure the relative surface coverage after each monomer addition via Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy, spectroscopic ellipsometry, reflection-absorption infrared spectroscopy, and cyclic voltammetry. Nuclear reaction analysis was also employed for the first time on a SAM to calculate the surface coverage of carbon atoms after each stepwise addition. These six different analysis methods indicate that the average extent of reaction is 99% for each addition step. The high yield and molecular surface coverage confirm the efficacy of Schiff base chemistry, at least with the terephthalaldehyde and 1,4-benzenediamine monomers, for preparing high-quality molecular films with π conjugation normal to the substrate.

Original languageEnglish (US)
Pages (from-to)8819-8828
Number of pages10
JournalJournal of the American Chemical Society
Volume137
Issue number27
DOIs
StatePublished - Jul 15 2015

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