Spectroscopic characterisation of copper acetohydroxamate and copper n-octanohydroxamate

The nature of the bonding in acetohydroxamic acid, copper acetohydroxamate and copper n-octanohydroxamate has been investigated by chemical analysis, XPS, FTIR and Raman spectroscopy. Vibrational spectra show the acid to be in the keto Z conformation as was previously established for the n-octano homologue. Chemical analysis established that the copper compounds have a copper:hydroxamate stoichiometry of 1:1. XPS confirms that they are Cu^II compounds. The absence of vibrational spectral bands that were previously identified with N-H vibrations for n-octanohydroxamic acid and its potassium compound, together with the presence of a CN stretch band that shifts when the nitrogen is labelled with ¹⁵N, confirms that the hydroxamate moieties in the Cu^II compounds are in the enol configuration. Some interaction between Cu and N is indicated by the spectra and could explain the 1:1 stoichiometry of the Cu^II hydroxamates investigated.