An efficient non-reaction based colorimetric and fluorescent probe for the highly selective discrimination of Pd-0 and Pd2+ in aqueous media

摘要

A novel anthraquinone-imidazole based colorimetric and fluorogenic probe 1 is synthesized, which can discriminate the oxidation states of palladium(Pd-0 and Pd2+) by naked eye with high selectivity in aqueous media owing to the difference in coordination within the right sized pocket of the probe molecule. The experimental results (fluorescence, UV/Vis and H-1 NMR spectroscopy) aided by density functional theory (DFT) calculations reveal that charge transfer (CT) is the main cause of the selective detection of the oxidation states of palladium. In the 1-Pd2+ complex, which is deficient in electrons, all the electron transitions represent electron transfers from the probe molecule to the central metal atom i.e. partial ligand-to-metal transition excitation while electronically filled Pd-0 shows electron transfers from the metal atom to the probe ligand i.e. partial metal-to-ligand transition excitation.