Selectivity in changes of fluorescence emission of 1,4-naphthoquinone derivatives by manganese and cadmium ions

Interactions of various metal ions with pyridine tethered 1,4-naphthoquinone derivatives (1-4) are studied by fluorescence spectroscopy. The fluorescence emission of 2-(pyridine-2-yl-methylamino) naphthalene-1,4-dione (1) is influenced by various metal ions and show highly selective fluorescence emission with Mn2+ ions and fluorescence ON and OFF states can be generated at different concentrations of Mn2+ ions. Sequential addition of Ni2+ and Mn2+ ions to a solution of I also generates ON and OFF emission states. The fluorescence responses towards the metal ions by two isomers 2-(pyridine-nyl-methylamino)naphthalene-1,4-dione (n = 3,4) are non-specific. The 2-(pyridine-2-yl-ethylamino)naphthalene-1,4-dione (4) shows fluorescence response to various metal ions; but its fluorescence response upon interaction with cadmium ions is very unique. Three stages in emission upon increase in concentration of Cd2+ ions, namely OFF-ON-ON are observed. (C) 2012 Elsevier Ltd. All rights reserved.