Spectrophotometric and spectrofluorimetric studies on the selective sensing of fluoride ions by Co(II) and Ni(II) complexes of naphthoquinone derivative possessing enhanced H-bonding property

A novel colorimetric chemosensor based on aminonaphthoquinone (L) bearing an N-H receptor unit directly attached to quinone signaling unit has been designed, synthesized and demonstrated. The ligand showed a highly selective colorimetric response to fluoride ions based on H-bond formation with the receptor unit. The binding constants of the L and its square planar [Co(L)Cl-2]center dot 3H(2)O and [Ni(L)Cl-2]center dot 4H(2)O complexes, computed using fluorescent enhancement data, were found to be 0.6, 1.5 and 0.9 x 10(8) M-1, respectively, indicating enhancement of H-bond donor ability of the receptor unit, as a result of complexation with metal ions, towards fluoride ion sensing. Also, these sensors had high selectivity for fluoride ion detection over other common anions, such as Cl-, Br-, I-, AcO-, NO3-, H2PO4- and CN- in acetonitrile. (C) 2012 Elsevier B.V. All rights reserved.