The Infrared Absorption Spectra of Nickel Metal Surfaces Modified with Optically Active α-Alanine from Its Aqueous Solution

Abstract

Abstract The infrared absorption spectra of thin films of α-alanine formed on pure nickel and “Raney nickel” surfaces, modified with its aqueous solution, were measured by the high-sensitivity reflection method. From the infrared dichroism in the reflection spectra, the molecular orientations in the thin films were derived. In the thin film formed on pure nickel modified at 5 °C, the CO2− group of α-alanine is oriented nearly vertical to the metal surface and the O···O axis is inclined to the surface. On the other hand, when the “Raney nickel” film is modified at 5 °C, the Cα–Co(carboxylate) bond is oriented obliquely to the surface. When the “Raney nickel” film is modified at 100 °C, the Ni-alanine chelate is formed on the surface: the Cα–Co bond and the NH2 group are nearly parallel to the substrate surface, while the O···O axis is vertical to that surface.