Applied Surface Science 44 (1990) 301-308 301 North-Holland X-RAY PHOTOELECTRON SPECTROSCOPIC AND X-RAY DIFFRACTOMETRIC CHARACTERIZATION OF ALKYLIMIDAZOLE FILMS ON COPPER OXIDE AND ALKYLIMIDAZOLATO COPPER(II) COMPLEXES S. YOSHIDA, H. ISHIDA * Department of Macromolecular Science, Case Western Reseroe University, Cleveland, OH 44106, USA and J.S. JEN Research and Development Division, Owens-Corning Fiberglass Corporation, Granville, OH 43023, USA Received 4 December 1989; accepted for publication 17 February 1990 The molecular structures of 2-undecylimidazole films on copper and copper oxide are studied using XPS with the reference of synthesized 2-undecylimidazolato copper(II). X-ray diffractograms of synthesized 2-alkylimidazole complexes are studied in order to understand the molecular structure of alkylirnidazole complexes. The difference in molecular structure between the synthesized complexes and the films on copper is discussed. The XPS spectra in the Cu2p region indicate Cu(II) complex regardless of the oxidation state of the copper substrates. The O ls peaks appeared at a binding energy higher than corresponding to oxide indicating the presence of water or peroxide between the copper ions. A linear relationship between the d(200) spacing of 2-alkylimidazole complexes and the number of carbons of alkylimidazole complexes indicates the same flat orientation of alkylimidazoles around the copper ions. The difference between the infrared spectra of imidazole films on copper and synthesized complex is due to the amorphous structure of the film. 1. Introduction A good knowledge on the molecular structure of imidazoles on copper is important for under- standing the mechanism of corrosion inhibition. Evaluations of imidazole derivatives as inhibitors and/or anti-corrosion chemicals have been carried out in several publications [1-5], from which the usefulness of the imidazole derivatives was evi- dent. However, only a few papers [6,7] reported the molecular structure of imidazole derivatives on copper. Imidazoles were initially studied because they possess a similar molecular structure to ben- zotriazole. Benzotriazole is useful and is widely used as an inhibitor for copper [8-10]. However, the molecular structure of benzotriazole is not well understood in spite of intensive study. Imidazoles * To whom correspondence should be addressed. can overcome the disadvantages of benzotriazole: the loss of anti-corrosion ability in water [11,12]. Copper plate with a benzotriazole pre-treatment does not show any anti-corrosion effect without benzotriazole in water [11]. On the other hand, imidazole pre-treatment indicates an excellent anti-corrosion effect even in water [12]. Also, a much faster rate of alkylimidazole film formation, which is the most important factor for an anti-cor- rosion film, was reported when compared to ben- zotriazole [13]. From these points of view, an extensive study of imidazole derivatives is war- ranted. X-ray photoelectron spectroscopy (XPS) is a useful technique for a surface study as it identifies not only the surface species, but also its chemical state. Tompkins and Sharma [6] reported that the valence state of a Cu-benzimidazole surface com- pound is cuprous. We used XPS to study 2-unde- 0169-4332/90/$03.50 © 1990 - Elsevier Science Publishers B.V. (North-Holland)