A study of the luminescent complexes formed by the dye 1,4-dihydroxyanthraquinone (quinizarin) and Ga(III) and In(III)

Fluorescent species form when Ga(III) and In(III) ions interact with 1,4-dihydroxyanthraquinone (quinizarin), in aqueous and non-aqueous media. Time dependence, temperature, solvent, counterion and pH effects studies have been performed in order to interpret the behaviour of this ligand in the presence of Ga(III) and In(III) ions. arin by itself is not fluorescent, but both its absorbance and fluorescence intensity increase proportionally to the complexation with Ga(III) and In(III), thus suggesting the supramolecular nature of these complexes, which could be used as fluorescence sensors. uorescent quantum-yield values of the QNZ complexes with Al(III), Ga(III) and In(III) ions are negatively affected by the increase of the size of M(III) ions, suggesting that the increase in metal size weakens the supramolecular interaction with QNZ. iometric studies, performed between pH 3 and 6, suggest the formation of 2:1 QNZ/In(III) species, having a high β formation constant.