Fluorescent character of Cu(I/II) complexes with bisquinoline-based ligands and fluorometric detection of reductants

The fluorescence ligands N,N'-bis(2-methylquinolyl)dimethylethylenediamine (BQDMEN) and N,N'-bis(2-methylquinolyl)dimethyl-1,3-propanediamine (BQDMPN) were synthesized. [Cu(II)(bqdmen)](2+) and [Cu(II)(bqdmpn)](2+) were prepared, and their reduction to [Cu(I)(bqdmen)](+) and [Cu(I)(bqdmpn)](+) was confirmed by the observed UV-Vis spectral change. Then, the fluorescence of [Cu(I/II)(bqdmen)](+/2+) and [Cu(I/II)(bqdmpn)](+/2+) in aqueous solution was characterized; [Cu(I)(bqdmen)](+) and [Cu(I)(bqdmpn)](+) were found to fluoresce in aqueous solution, whereas the fluorescence of [Cu(II)(bqdmen)](2+) and [Cu(II)(bqdmpn)](2+) was completely quenched. On the basis of these findings, fluorometric detection of reductants with a flow-injection system using a [Cu(II)(bqdmen)](2+) or [Cu(II)(bqdmpn)](2+) solution as a carrier was explored.