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Comparison of the Electrochemical Properties of Two Structurally Different Novel bis-Schiff Bases

Two novel symmetrical bis-Schiff bases ((1E)-1-N-{; ; ; ; [4-(4-{; ; ; ; [(E)-N-(2-aminophenyl) carboxyimidoyl] phenoxy}; ; ; ; butoxy) phenyl]methylidene}; ; ; ; benzene-1, 2-diamine (compound 1) and (1E)-1-N-{; ; ; ; [4-(4-{; ; ; ; [(E)-N-(4-aminophenyl) carboxyimidoyl] phenoxy}; ; ; ; butoxy) phenyl]methylidene}; ; ; ; benzene-1, 4-diamine (compound 2) were synthesized and characterized by means of single-crystal X-ray diffraction (1), FT-IR and NMR spectroscopy (1, 2), elemental (1, 2), TG/DSC and electrochemical analysis (1, 2). The prepared compounds are positional isomers that display very different electrochemical behaviour. Electrochemical study has shown that the oxidation of the investigated Schiff base (1) is irreversible, diffusion controlled process and that the oxidation products are adsorbed on the glassy carbon electrode surface. Oxidation of a Schiff base (2) is reversible (follows EC reaction mechanism), diffusion controlled and the oxidation products are also adsorbed on the glassy carbon electrode surface. Considering molecular structure of compounds, molecule 1 is planar, with small deviation of atoms from the calculated plane. The planarity of molecule 1 is stabilized by untypical intramolecular interaction of amino and imino nitrogen atoms. In the crystal, the molecules are primarily linked by hydrogen bonds involving primary amino groups and weak C-H•••π interactions. Consequently, these interactions are arranging molecules into herringbone packing motif. Crystal structure of molecule 2 could not be determined but it is predicted based upon similarity with molecule 1 and interpretation of the spectral data (NMR and FTIR).

voltammetry; structure related electrochemical properties; bis-Schiff base; single-crystal X-ray analysis; NMR; IR; TG/DSC

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