Characterization of copper heterocyclic compounds: X-ray photoelectron spectroscopy study

Abstract

Several Cu–azole complexes were synthesized by mixing solutions of cupric chloride and an azole ligand at the appropriate metal-to-ligand ratio. The products were isolated as powders and analyzed by elemental analysis, diffuse reflectance Fourier transform infrared spectroscopy, and x-ray photoelectron spectroscopy. Both the bulk and the surface elemental atomic ratios were identical suggesting no surface reconstruction. This paper primarily addresses the radiation effect on the surface composition of the exposed powder. All powders exhibited Cu(2p) line shape typical of paramagnetic copper; no elemental or diamagnetic copper atoms were observed over a very short period of exposure to x radiation. The position and intensity of the Cu(2p) shakeup satellite revealed differences among the complexes that can be attributed to the nature of the azole ligand and to the coordination geometry. Upon exposure to x radiation or electron beam no change was observed in the relative atomic ratios; however, a new peak evolved on the low-binding-energy side of the Cu(2p) suggesting the formation of diamagnetic copper. The evolution of the Cu+1/Cu+2 ratio and the relative intensity of the shakeup satellite suggested that radiation affects the coordination geometry and electronic structure of the surface layers of these complexes.