Imine ligands based on ferrocene: Synthesis, structural and Mössbauer characterization and evaluation as chromogenic and electrochemical sensors for Hg2+

The compounds 1-naphthyliminoferrocene, 1, and 2-methyl-1-naphthyliminoferrocene, 2, were prepared by the reaction of ferrocenecarboxaldehyde and the corresponding amine, 1-naphthylamine and 2-methyl-1-naphthylamine with one drop of pyrrolidine as the catalyst, in CH₂Cl₂, under an inert atmosphere. The compounds were fully characterized by elemental analyses, matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF), FT-IR, ¹H and ¹³C NMR as well as two-dimensional, NOESY, COSY and HSQC, NMR spectroscopy. Mössbauer spectroscopic studies were performed to characterize iron species in both compounds. The solid-state molecular structures of compounds 1 and 2 were determined by single crystal X-ray diffraction. Analysis of the electrochemical behaviour of complexes 1 and 2 was performed by cyclic and square wave voltammetry. Compounds 1 and 2 were tested as chromogenic and electrochemical sensors for Hg²⁺.