FLUORESCENCE QUENCHING AND COPPER COMPLEXATION BY A CHESTNUT LEAF LITTER EXTRACT - SPECTROSCOPIC EVIDENCE

Fluorescence quenching on addition of Cu(II) to aqueous solutions of chestnut (Castanea sativa L. ) leaf litter extract (LLE) has been interpreted previously in terms of Cu complexation by LLE organic ligands. In order to provide direct evidence for the existence of these complexes, as well as information about their coordination structures, infrared (IR) and electron spin resonance (ESR) spectroscopy were applied to investigate Cu/LLE mixtures that showed increasing fluorescence quenching with increasing pH. The Cu/LLE mixtures were prepared with approximately equimolar concentrations of Cu and LLE binding sites (200 mmol m** minus **3) at pH values in the range 4 to 7. The IR spectra indicated the existence of Cu complexes involving carboxylate groups, even at pH 4.