Ion-sensing properties of ferrocenyl-diaminomaleonitrile derivatives.

Abstract

Mono- (1) and bis (2) -substituted Shiff bases obtained by the reaction between ferrocenecarbaldehyde and diaminomaleonitrile were prepared and characterized by 1H and 13C NMR, IR, UV-vis spectroscopy methods, elemental analysis, and X-ray crystallography. Electrochemical techniques were employed to investigate the possibility of a mixed-valence state of the iron centers in 2, which are connected by a conjugated π-system. Two reversible oxidation potentials were observed in cyclic voltammetry, and spectroelectrochemical experiments revealed the presence of low-energy inter-valence charge transfer band in 2+, corresponding to a weakly-coupled class II system. Both complexes were tested for cation-recognition properties using a variety of main group and transition-metal cations. It was shown that the complex 1 can be used as a selective optical sensor in recognition of Hg(II) and Ag(I) ions.