Copper(II) complex as selective turn-on fluorescent probe for nitrite ion

•Cu(II) complex of 3-(pyren-8-yl)-1-(pyridine-2-yl)prop-2-en-1-one with a fluorophore was prepared.•Addition of aqueous nitrite to acetonitrile solution of the complex resulted in reduction of Cu(II) center.•Nitrite ion was oxidized to nitrate during the reaction. Labeling studies suggested water as the source of oxygen atom.•The reduction of Cu(II) center restored the quenched fluorescence intensity of the ligand in the complex.

The Cu(II) complex, 1 of a chalcone ligand L, [L = 3-(pyren-8-yl)-1-(pyridine-2-yl)prop-2-en-1-one] with a fluorophoric group has been prepared. In acetonitrile solution, the copper(II) center of complex 1 was found to undergo reduction upon addition of aqueous nitrite. The nitrite ion was found to be oxidized to nitrate during the reaction. Titration experiment revealed that 0.5 equivalent of nitrite ion is required for the stoichiometric conversion from copper(II) to copper(I). Labeling studies suggested water as the source of oxygen atom in the process. The reduction of copper(II) center restored the quenched fluorescence intensity of the ligand in the complex and thus can be utilized as turn-on fluorescent sensor for nitrite.

Graphical abstractCopper(II) complex 1 of a chalcone ligand L, [L = 3-(pyren-8-yl)-1-(pyridine-2-yl)prop-2-en-1-one] with a fluorophoric group has been prepared. Addition of aqueous nitrite solution to the methanol or acetonitrile solution of the complex resulted in reduction of copper(II) center. The nitrite ion was found to be oxidized to nitrate during the reaction. The reduction of copper(II) center restored the quenched fluorescence intensity of the ligand in the complex and thus can be utilized as turn-on fluorescent sensor for nitrite.Figure optionsDownload full-size imageDownload as PowerPoint slide