Synthesis and electrocatalytic activity towards oxidation of hydrazine of a new family of hydroquinone salophen derivatives: application to the construction of hydrazine sensors

For the first time DHsalophen tetradentate ligands, were DHsalophen denotes N,N′-bis(dihydroxybenzylidene)-1,2-diaminobenzene, have been synthesized by combination of ortho-phenylenediamine and the corresponding isomer of the dihydroxybenzaldehyde in a solvent free system. These ligands containing ortho- and para-quinone functional groups were characterized using UV-vis and FTIR spectroscopies, elemental analysis and cyclic voltammetry in non aqueous solvents, such as dimethylformamide. Adsorption of these compounds onto glassy carbon (GC) electrodes gives rise to stable and redox active films. These modified electrodes present an electrochemical response strongly dependent on pH as can be anticipated for quinone/hydroquinone functional groups confined at the electrode surface. GC electrodes modified with films derived from 3,4-Dhsalophen exhibit a potent and persistent electrocatalytic activity towards the electrooxidation of hydrazine. In addition, the catalytic currents were proportional to the concentration of hydrazine giving rise to calibration curves characterized by two linear segments. The linear segment over the concentration range of 0.010-0.400 mM could be used with analytical purposes to determination of hydrazine with a detection limit of 1.6 μM and a sensitivity of 17.04 μA mM−1. These modified electrodes has been applied to the construction of hydrazine sensors and could be employed as redox mediators in the design of biosensors based on redox enzymes.