The Effect of Adsorbed Amines on the ESR of Copper Oxide

概要

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The effect of several additives on the ESR of copper oxide was studied. Among the additives studied, amines and NH3 had peculiar effects on the ESR spectra. From the spectrum formed by NH3 it is concluded that the (Cu–NH3)2+ complex cation is formed on the surface of a CuO particle. The formation of this complex cation obeyed a pseudo-flrst-order rate and can be interpreted in terms of the surface reaction between the exposed Cu2+ and NH3. Among the amines studied, only primary amines gave ESR spectra which provide evidence for the existence of (Cu-amine)2+complex cations. The foregoing fact and the results obtained on the three isomers of chloroaniline indicate that a strong s-character of the lone-pair orbital is needed if an amine molecule is to occupy a surface defect of the O2−, by which the Cu2+ is exposed on the surface, thus forming a complex cation. By these facts, the d-orbital of Cu2+, which can overlap with the nitrogen lone pair of the amine molecule, is concluded to be dz2. The three principal values of the g-tensor for the (Cu–NH3)2+complex cation depend greatly on the temperature, indicating that this cation has some rotational and vibrational motions below 130°C, at which point Cu2+ and NH3 dissociate.
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