The spectroscopic study of formation of complexes of quercetin and onion scale dye with metal ions

The influence of metal ions on the change of the electronic spectra of quercetin and onion scale dye in ethanol and in a binary mixture of ethanol+water was studied. It is shown that adding metal salts of nickel acetate, copper sulfate and aluminum in the binary mixture of 1% ethanol+99% water gives rise to appearance of a new absorption band on the long wavelength side due to the formation of complexes between the molecules of quercetin and onion scale dye with metal ions. Quantum-chemical calculations showed that the complexation is carried out by means of the oxygen atoms of the carbonyl groups of the molecules. (authors)