Spectroscopic Properties of Some Metal Complexes of Gossypol
The spectroscopic properties of a number of important metal-gossypol complexes have been studied and compared with those of 2-hydroxy-l-naphthaldehydes. Gossypol and its derivatives exhibit three bands, α, β, and p. The α and β bands are assigned to π→π * transitions and the p-band to electronic transition from highest occupied to lowest unoccupied molecular orbital. In the complexes, the α-band is shifted to longer wavelengths and the p-band disappears. The infrared spectra of gossypol exhibits a strong band at 6.lµ (C-O stretching); but in the complexes, this band disappears and a new band at 5.7 µ appears. The infrared data on 2-hydroxy-l-naphthaldehyde-anthranilic acid indicates that carbonyl groups are involved in a salt-type linkage (dimer) with copper atoms. Electronic absorption spectra of several Schiff base complexes of 2-hydroxy-l-naphthaldehyde, in conjunction with magnetic susceptibility data, are evaluated to draw conclusions on the structure of gossypol complexes.
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